Simrad PI44 Installation Manual

Installation manual

Simrad PI44
Catch monitoring system

www.simrad.com

M A X I M I Z I N G Y O U R P E R F O R M A N C E A T S E A

851-165101 / Rev.A

Simrad PI44

Catch monitoring system

Installation manual

NOTICE

Operation of the PI44 system assumes that the
communication between the Operator Unit and the
sensors is fully functional. Ensure that the
communication channels defined on the Operator Unit
matches those of the sensors.

About this document

Rev Date Written by Checked by Approved by

Rev.A

03.06.05 RBr KR KR

Original issue.

© 2005 Simrad AS
ISBN 82-8066-048-8
All rights reserved. No part of this work covered by the copyright hereon may be

reproduced or otherwise copied without prior permission from Simrad AS.
The information contained in this document is subject to change without prior notice.

Simrad AS shall not be liable for errors contained herein,or for incidental or consequential
damages in connection with the furnishing, performance, or use of this document.

The equipment to which this manual applies must only be used for the purpose for which
itwasdesigned.Improperuseormaintenancemay causedamagetotheequipment or injury
topersonnel. The usermustbefamiliar with the contentsof the appropriate manuals before
attempting to operate or work on the equipment. Simrad AS disclaims any responsibility
fordamageorinjurycausedbyimproperinstallation,useormaintenanceoftheequipment.

If you require maintenance on your Simrad equipment, contact your local dealer. You can
also contact Simrad using the following e-mail address: [e-mail]

Sections

1Introduction

This section provides a general introduction to the PI44 installation. Refer
to page 1.

2 Echo sounder transducer installation

This section provides general guidelines for the installation of the optional
echo sounder transducer. Refer to page 18.

3 Purse hydrophone installation

This section provides general guidelines for the installation of the PI44
purse seine hydrophone. Refer to page 42.

4 Trawl hydrophone installation

This section provides general guidelines for the installation of the PI44
trawl hydrophone. Refer to page 79.

Installation manual

5 Portable hydrophone

This section provides general guidelines for the use of the PI44 portable
hydrophone. Refer to page 120.

6OperatorUnit

This section explains how to install the PI44 Operator Unit cabinet. Refer to
page 127.

7Sensors

This section provides an introduction to PI44 sensors and the configuration
of these. Refer to page 133.

8 Cable layout

This section details all cabling. Refer to page 142.

9Interfacesetup

This section explains how to connect external equipment, such as navigation
and positioning sensors. Refer to page 165.

10 Installing sensor adapters

This section explains how to install the PI Spread and PI Remote sensors on
the trawl doors. Refer to page 179.

11 Software updates

If you need to upgrade the software in your PI44 Operator Unit, the necessary
procedures can be found here. Refer to page 194.

851-165101 / Rev.A

I

Simrad PI44

1 INTRODUCTION 1.........................................

System diagram 2..........................................

Scope of supply 3..........................................

Supply conditions 5........................................

General installation requirements 6............................

Equipment handling 7......................................

11 TRANSDUCER INSTALLATION 18..........................

Purpose 18................................................

Transducer location 19.......................................

External mounting 23........................................

Transducer blister 28........................................

Box keel 33...............................................

Cable glands 35............................................

Cable in steel conduit 39.....................................

Handling and maintenance 40.................................

Approved anti-fouling paints 41...............................

12 PURSE SEINE HYDROPHONE 42...........................

Purpose 42................................................

Installation precautions 43....................................

Considerations 44...........................................

Pre-installation check-list 48..................................

Optimal location of purse seine hydrophones 50...................

Coverage area, orientation and tilt 51...........................

Mounting arrangement 54....................................

Dual hydrophone installation 57...............................

Hydrophone protection 59....................................

Hydrophone cable 62........................................

Installation drawings 67......................................

13 TRAWL HYDROPHONE 79...................................

Purpose 79................................................

Installation precautions 80....................................

Considerations 81...........................................

Pre-installation check-list 86..................................

Optimal location of trawl hydrophones 88.......................

Coverage area, orientation and tilt 91...........................

Mounting arrangement 95....................................

Dual hydrophone installation 101...............................

Hydrophone protection 102....................................

Hydrophone cable 105........................................

II

851-165101 / Rev.A

Installation manual

Installation drawings 110......................................

14 PORTABLE HYDROPHONE 120...............................

Purpose 120................................................

General guidelines 121........................................

Deployment over the side 122..................................

Paravane arrangement 123.....................................

Portable hydrophone storage 126................................

15 OPERATOR UNIT 127.........................................

Purpose 127................................................

Installation choices 128.......................................

16 SENSORS 133.................................................

Introducing the sensors 134....................................

Sensor configuration 139......................................

8 CABLE LAYOUT 142..........................................

System cabling 143..........................................

Cable plan 144..............................................

Cable specifications 146......................................

Basic cabling requirements 162.................................

19 INTERFACE SETUP 165.......................................

Hydrophones 166............................................

Echo sounder transducers 167..................................

Positioning and navigation data 170.............................

Water depth, speed and temperature 173..........................

Data output on NMEA format 177..............................

NMEA Interface verification 178................................

20 INSTALLING SENSOR ADAPTORS 179......................

Introduction 179.............................................

Installation keypoints 180.....................................

Before work begins 183.......................................

Procedure 183...............................................

21 SOFTWARE UPDATES 194....................................

Overview 194...............................................

DSP Software upgrade 195....................................

MMI Software upgrade 199....................................

PI DSP Upload 202..........................................

851-165101 / Rev.A

III

Simrad PI44

IV

851-165101 / Rev.A

Introduction

1INTRODUCTION

The purpose of this manual is to provide the information and
basic drawings required for installation of the Simrad PI44 catch
monitoring system. These instructions must be followed
carefully to ensure optimal system performance. As a guide,
installation procedures are presented in the order they are to be
performed. After installation, this document must be stored on
board the vessel for later reference when updating or servicing
the equipment.

Note: The installer is responsible for the equipment during the

installation. The guarantee is only valid when the installation is
made in accordance with this manual.

Topics

→ System diagram, page 2
→ Scope of supply, page 3
→ Supply conditions, page 5
→ General installation requirements, page 6
→ Equipment handling, page 7

851-165101 / Rev.A

1

Simrad PI44

System diagram

(A) = Operator Unit
(B) = PI charger
(C) = Hydrophone

(provides communication
with the sensors)

(D) = Optional echo
sounder transducer.
Several types are
available.

(E) = Sensors mounted on
the net. Maximum six
sensors may be used
simultanously, and several
types are available.

(F) = Interfaces to
external sensors (serial
lines, NMEA format)

(G) = DC power input

2

851-165101 / Rev.A

Introduction

Scope of supply

Main units

The standard Simrad PI44 catch monitoring system is comprised
of the following main units. All must be ordered separately.

Unit Order number

Operator Unit PI3--208872

Hydrophone, purse seine HYD--202711

Hydrophone, trawl HYD--205254

Hydrophone, portable HYD--202713

Paravane kit for portable hydrophone KIT--207284

+24 Vdc 5 A Power supply (230 vac) 290--076359

+13,2 Vdc 10 A Power supply (230 vac) 290--087521

Echo sounder transducers

The echo sounder transducers are optional. Note that only one
of the echo sounder transducers is required. Only the
transducers recommended by Simrad for use with the PI44
system are listed.

Transducer Order number

38/200 Combi C KSV--202192

38/200 Combi D KSV--203004

38/200 Combi W KSV--208845

50/200 Combi C KSV--202193

50/200 Combi D KSV--203005

Sensors

The Simrad PI44 catch monitoring system can operate with six
sensors simultanously. Several sensor types are available.

Sensor Order number

PI Bottom Contact sensor PI3--207642

851-165101 / Rev.A

PI Catch sensor PI3--207641

PI Depth sensor, 300 m PI3--207637

PI Depth sensor, 600 m PI3--207638

PI Depth sensor, 1000 m PI3--207639

PI Height sensor PI3--280002

PI Spread sensor PI3--206869

3

Simrad PI44

Sensor Order number

PI Twin Spread sensor PI3--206896

PI Remote 1 sensor PI3--206870

PI Remote 2 sensor PI3--206871

PI Remote 3 sensor PI3--206872

PI Remote 4 sensor PI3--206885

PI Temperature sensor PI3--207640

Sensor chargers

In order to charge the PI44 sensor batteries, the following
charger is available.

Sensor Order number

PI Sensor charger LAD--207624

4

851-165101 / Rev.A

Introduction

Supply conditions

The following supply conditions are applicable to standard
Simrad PI44 deliveries and associated optional equipment.

Equipment responsibility

The shipyard performing the installation and/or dealer becomes
fully responsible for the equipment upon receipt unless
otherwise stated in the contract. The duration of responsibility
includes:

• The period of time the equipment is stored locally before
installation.

• During the entire installation process.

• While commissioning the equipment.

• The period of time between commissioning and the final

acceptance of the equipment by the end user (normally the
owner of the vessel which the equipment has been installed).

The Simrad PI44 system guarantee period (as specified in the
contract) begins when the acceptance documents have been
signed unless other arrangements have been made in the
contract.

Receipt, unpacking and storage

Upon accepting shipment of the equipment, the shipyard and/or
the dealer should ensure that the delivery is complete and
inspect each shipping container for evidence of physical
damage. If this inspection reveals any indication of crushing,
dropping, immersion in water or any other form of damage, the
recipient should request that a representative from the company
used to transport the equipment be present during unpacking.

All equipment should be inspected for physical damage, i.e.
broken controls and indicators, dents, scratches etc. during
unpacking. If any damage to the equipment is discovered, the
recipient should notify both the transportation company and
Simrad so that Simrad can arrange for replacement or repair of
the damaged equipment.

Once unpacked, the equipment must be stored in a controlled
environment with an atmosphere free of corrosive agents,
excessive humidity or temperature extremes. The equipment
must be covered to protect it from dust and other forms of
contamination when stored.

851-165101 / Rev.A

5

Simrad PI44

General installation requirements

Responsibility and approval

The Simrad PI44’s hydrophone and echo sounder i nstallation
must be approved on a case-by-case basis with regard to the
vessel’s national registry and corresponding maritime authority.
The shipowner and shipyard performing the installation are
responsible for obtaining installation approval.

Environmental requirements

All equipment, unless otherwise specified, must be protected
from temperature extremes and excessive humidity.

Compass deviation

Once the installation is complete, the vessel must be swung with
the PI44 system in both the operative and inoperative modes.
The shipowner and captain are responsible for updating the
deviation table accordingly with regard to the vessel’s national
registry and corresponding maritime authority.

Noise sources

The vessel’s hull, rudder(s) and propeller(s) should be
thoroughly inspected in dry dock prior to installation.
Roughness below the water-line deformities in the shell plating
and protruding obstacles can create underwater noise. These
sources of turbulence must be smoothed or removed as best as
possible. It is especially important that the propeller(s) is not
pitted or damaged.

Dry docking

Make sure that ample clearance under the hydrophone and e cho
sounder transducer is provided when dry docking the vessel.
Avoid locating supporting blocks or structures in the vicinity of
this equipment.

Note: The location of the hydrophone and echo sounder transducer

must be noted on the vessel’s docking plan for future reference.

Wiring

The cables from the wheelhouse to the hydrophone and echo
sounder transducer must be supported and protected along its
entire length using conduits and/or cable trays. Note that the
cables must not be installed in the vicinity of high-power
supplies and cables, antenna cables or other possible sources of
interferences.

6

851-165101 / Rev.A

Introduction

Equipment handling

The units may be supplied as spare parts, or as parts of a
delivery.

Transportation

Unless otherwise stated in the accompanying documentation,
electronic, electro-mechanical and mechanical units supplied by
Simrad can be transported using all methods approved for
delicate equipment; (by road, rail, air or sea). The units are to be
transported in accordance with general or specific i nstructions
for the appropriate unit(s), using pallets, transport cases, or
carton boxes as appropriate.

Note: Special local restrictions concerning air transportation may be

applied to units containing certain types of batteries. The units
should be checked and the regulations investigated by the
packer/shipper before the unit is dispatched.

All local transportation must be carried out according to the
same specifications as for the initial delivery. In general, all
units must be handled with care. The carton or case containing
the equipment must be kept dry at all times, and must be
sheltered from the weather. It must not be subjected to shocks,
excessive vibration or other rough handling.

The carton or case will normally be marked with text or symbols
indicating which way up it is to be placed. Follow any
instructions given and ensure the case is always placed with its
“top” uppermost.

The carton or case must not be used for any purpose for which it
was not intended (step, table, etc.), and in the absence of other
information, no other cartons or cases must be stacked on top of
it.

Lifting

A heavy crate will normally be marked with its weight, and the
weights of other cartons or crates will normally be entered on
the packing list.

851-165101 / Rev.A

• Always check the weight of a crate before attempting to lift
it.

• Always use lifting apparatus that is certified for the load.

7

Simrad PI44

Heavy units may be equipped with lifting lugs for transportation
by crane within the workshop or installation area. Before a crane
is used, check:

• The applicable weight certificate for the crane.

• The security of the lifting lugs.

Ensure that all available lifting lugs are used. Ensure the unit
remains under control during the operation to avoid damage to
the unit, equipment or personnel.

Heavy units may be transported using a fork-lift truck. Special
attention must then be paid to the position of the unit’s centre of
gravity. The units must be properly secured to the truck.

Initial preservation

When a system, a unit or a spare part has been delivered to the
customer, it may be subject to long-time storage prior to
installation and use. During this storage period, certain
specifications must be met.

The equipment must be preserved and stored in such a way that
it does not constitute any danger to health, environment or
personal injury.

Specific specifications are presented below.

→ For further information about storage, refer to page 12.
→ For further information about re-packing, refer to page 15.
→ For further information about temperature protection, refer to

page 17.

Preserving the original packing crate

1 The equipment must be stored in its original transportation

crate.

2 Ensure that the units are clearly separated in the shelves

and that each unit is easily identifiable.

3 The crate must not be used for any purpose for which it

was not intended (eg. work platform etc.).

4 The crates must not be placed on top of each other, unless

specific markings permit this.

5 The crates must not be placed directly on a dirt-floor.
6 Do not open the crate for inspection unless special

circumstances permit so.

- “Special circumstances” may be suspected damage to
the crate and its content, or inspections by civil
authorities.

8

851-165101 / Rev.A

Introduction

- If any units are damaged, prepare an inspection report
stating the condition of the unit and actions taken.
Describe the damage and collect photographic evidence
if possible. Re-preserve the equipment.

- If the units are not damaged, check the humidity
absorbing material. If required, dry or replace the bags,
then repack the unit(s) according to the packing
instructions.

7 If the crate has been opened, make sure that is it closed

and sealed after the inspection.

- Use the original packing material as far as possible.

→ Refer to information on page 15.

Ambient temperature and humidity during
storage

1 The storage room/area must be dry, with a non-condensing

atmosphere. It must be free from corrosive agents.

2 The storage area’s mean temperature must not be lower

than -30°C, and not warmer than +70° C.

- If other limitations apply, the crates will be marked
accordingly.

Note: Transducers must not be stored in temperatures below -20°C, or

higher than +60°C.

3 The crate must not be exposed to moisture from fluid

leakages.

4 The crate must not be exposed to direct sunlight or

excessive warmth from heaters.

Shock and vibration during storage

1 The crate must not be subjected to excessive shock and

vibration.

851-165101 / Rev.A

ESD precautions during storage

→ Refer to the information on page 16.

If the unit contains normal batteries, these may have been
disconnected/isolated before the unit was packed. These must
only be reconnected before the installation starts. Units
containing batteries are marked.

9

Simrad PI44

Caution: Units containing lithium or alkaline batteries must be

handled separately and with care. Such units are
marked accordingly. Do not attempt to recharge such
batteries, open them or dispose of them by
incineration. Refer to the applicable product data
sheets.

Inspection and unpacking

An inspection must be carried out immediately after the unit(s)
have arrived at their destination.

• Check all wooden or cardboard boxes, plastic bags and
pallets for physical damage. Look for signs of dropping,
immersion in water or other mishandling.

• If damage is detected externally, you will have to open the
packaging to check the contents.

- Request a representative of the carrier to be present while

the carton is opened, so any transportation damage can be
identified.

• If any units are damaged, prepare an inspection report stating
the condition of the unit and actions taken. Describe the
damage and collect photographic evidence if possible. Send
the inspection report to Simrad as soon as possible.

• If the units are not damaged, check the humidity absorbing
material. If required, dry or replace the bags, then repack the
unit(s) according to the packing instructions.

Inspection and unpacking: General procedure

Normal precautions for the handling, transportation and storage
of fragile electronic equipment must be undertaken.

Note: If the unit is not to be prepared for immediate use, you may

consider storing it unopened in its original packing material.
However, it may be useful to open the case to check its contents
for damage and retrieve any accompanying documentation.

10

• Check the carton before opening it to ensure it shows no
signs of dropping, immersion in water or other mishandling.

- If the carton shows signs of such damage, refer to the

paragraph covering Inspection on receipt.

851-165101 / Rev.A

Introduction

• Place the carton on a stable work bench or on the floor with
the top of the carton uppermost.

• In the absence of other instructions, always open the top of
the carton first. The contents will normally have been
lowered into the carton from above, so this will usually be
the easiest route to follow.

- Care must be used when opening the carton to ensure the

contents are not damaged.

Caution: Do not use a knife to open cardboard cartons - the

contents may lie close to the surface, and may be
damaged by the blade.

• If the carton has been closed using staples, remove the staples
from the carton as you open it. This will reduce the
possibilities of scratch injury to yourself and damage to the
contents.

• If a wooden crate has been closed using screws, always
remove them using a screw-driver. Do not attempt to prise
the lid off with a crow-bar or similar.

• Once the carton is open, carefully remove all loose packing
and insulation material. Check for manuals and other
documents that may have been added to the carton during
packing, and put these to one side. Check also for special
tools, door keys etc.

Unpacking electronic and electro-mechanical
units

Caution: Beware of the dangers of Electro-Static Discharge

(ESD) both to yourself and to the equipment, when
handling electronic units and components. Refer to the
precautions starting on page 16.

Electronic and electro-mechanical units will normally be
wrapped in a clear plastic bag. Lift the unit, in its bag, out of the
carton and place it in a stable position on the floor/work bench.

Inspect the unit for damage before opening the plastic bag.

Note: Cables must never be used as carrying handles or lifting points.

851-165101 / Rev.A

11

Simrad PI44

Note: Do not break the seal to open a circuit board package before the

board is to be used. If the board package is returned to the
manufacturers with the seal broken, the contents will be
assumed to have been used and the customer will be billed
accordingly.

Assuming all is well, open the bag and remove the unit.
Open the unit and check inside. Remove any packing and

desiccant material that may be inside.

Unpacking mechanical units

Mechanical units may be heavy. Using a suitably certified lifting
apparatus, lift the unit out of the crate and place it in a stable
position on the floor/work bench.

Inspect the unit for damage and remove any packing material
that may be inside the unit.

Unpacking transducers

Transducers may be supplied mounted to a hull unit (if any), or
packed separately. Crates are normally identified by the order
number and the serial number.

The transducer face must be protected by a rigid, padded cover
(e.g. a wooden box lined with foam rubber) all the time it is
exposed to the risk of physical damage.

Note: Once the units are unpacked, great care must be taken to ensure

that transducers and cabling are not exposed to any mechanical
stress.

Re-packaging

If the unit is not to be installed immediately, re-pack it in its
original packing material to prevent damage in the intervening
period.

12

→ Refer to the information on page 15.

Pre-installation storage

The equipment should be stored in its original transportation
crate until ready for installation. The crate must not be used for
any purpose for which it was not intended (eg. work platform
etc.).

851-165101 / Rev.A

Introduction

Once unpacked, the equipment must be kept in a dry, non
condensing atmosphere, free from corrosive agents and isolated
from sources of vibration.

Note: Do not break the seal to open a circuit board package before the

board is to be used. If the board package is returned to the
manufacturers with the seal broken, the contents will be
assumed to have been used and the customer will be billed
accordingly.

The unit must be installed in its intended operating position as
soon as possible after unpacking.

If the unit contains normal batteries, these may have been
disconnected/isolated before the unit was packed. These must
then be reconnected during the installation procedure. Units
containing batteries are marked.

Caution: Units containing lithium or alkaline batteries must be

handled separately and with care. Such units are
marked accordingly. Do not attempt to recharge such
batteries, open them or dispose of them by
incineration. Refer to the applicable product data
sheets.

After use storage

If a unit is removed from its operating location and placed into
storage, it must be properly cleaned and prepared before
packing.

Cleaning cabinets

If a cabinet has been exposed to salt atmosphere while it was in
use, it must be thoroughly cleaned both i nternally and externally
to prevent corrosion.

• Wipe the cabinet externally using a damp cloth and a little
detergent. Do not use excessive amounts of water as the unit
may not be water tight. On completion, dry the unit
thoroughly.

851-165101 / Rev.A

• All surfaces must be inspected for signs of corrosion, eg.
flaking/bubbling paint, stains etc. Damaged or suspect areas
must be cleaned, prepared and preserved using the correct
preservation mediums for the unit. The mediums to be used
will usually be defined in the units’ maintenance manual.

13

Simrad PI44

• Open the unit, and using a vacuum cleaner, remove all dust
etc. from the unit. Great care must be taken to ensure the
circuit boards and modules are not damaged in the process.

Mechanical units

If a mechanical unit may have been exposed to a salt
atmosphere while it was in use, it must be thoroughly cleaned
both internally and externally to prevent corrosion.

• If the construction materials and type of unit permits, wash
the unit using a high-pressure hose and copious amounts of
fresh water.

Examples:

- The lower parts of hull units (outside the hull)

- Subsea units

• Ensure that all traces of mud and marine growth are removed.
Use a wooden or plastic scraper to remove persistent growth,
barnacles etc. On completion, dry the unit thoroughly.

Caution: Do not use a high pressure hose in the vicinity of cables

or transducers. Do not use sharp or metal tools on a
transducer face.

• If the materials or type of unit prevents the use of a
high-pressure hose, wipe the unit using a cloth dampened
with water containing a little detergent.

Examples:

- The upper parts of hull units (inside the hull)

- Hydraulic systems

• Do not use excessive amounts of water as some components
on the unit may not be water tight. Wipe off the detergent
with a damp cloth, then dry the unit thoroughly.

• All surfaces must be inspected for signs of corrosion, eg.
flaking/bubbling paint, stains etc. Damaged or suspect areas
must be cleaned, prepared and preserved using the correct
preservation mediums. The mediums to be used will
normally be defined in the unit’s maintenance manual.

14

Cables

Wipe clean all exposed cables, and check for damage. If a cable
shows signs of wear or ageing, contact Simrad for advice.

851-165101 / Rev.A

Introduction

Internal batteries

If the unit contains batteries, these may discharge slowly during
storage. If the unit is to be stored for an extended period,
disconnect or remove all internal batteries.

A suitable piece of insulating material can be placed between
the battery and the electrical contacts to prevent electrical
discharge. The battery can then remain in the unit, reducing the
risk of it being misplaced during the storage period.

Caution: Units containing lithium or alkaline batteries must be

handled separately and with care. Such units are
marked accordingly. Do not attempt to recharge such
batteries, open them or dispose of them by
incineration. Refer to the applicable product data
sheets.

Dehumidifier

Place a suitably sized bag of desiccant material (silica gel or
similar) into the unit to keep the electronic components as dry as
possible.

Coatings

Spray the unit externally with a corrosion inhibitor (e.g. a light
oil) before packing.

Re-packing

The unit should be stored and transported in its original packing
material and/or crate. In the event that this material is not
available, proceed as follows:

• Small units must be protected from damp by being placed
within a plastic bag at least 0.15 mm thick. An appropriate
quantity of desiccant material should be placed inside this
bag, and the bag sealed. The sealed unit must then be placed
in an appropriate carton or crate, and supported in the
container by appropriate shock-absorbing insulation
(polystyrene foam chips etc.).

851-165101 / Rev.A

• Large units must be placed in a suitable cardboard box or
wooden crate. The unit must be protected against physical
damage by means of shock-absorbing insulation mats. The
box must be clearly marked with its contents, and must be
stored in a dry and dust-free area.

15

Simrad PI44

ESD precautions

Electro-Static Discharge (ESD) is the transfer of an electrostatic
charge between two bodies at different electrostatic potentials,
caused either by direct contact or induction by an electrostatic
field.

The passing of a charge through an electronic device can cause
localised overheating, and it can also “puncture” insulating
layers within the structure of the device. This may deposit a
conductive residue of the vaporised metal on the device, and
thus create a short circuit. This may result in a catastrophic
failure, or degraded performance of the device.

Sensitive electronic equipment must be transported and stored in
protective packing bags, boxes and cabinets. The equipment
must NOT be transported or stored close to strong electrostatic,
electro-magnetic or radioactive fields.

If it is necessary to open and touch the electronics inside the
boxes/cabinets, then the following precautions MUST be taken:

• The working area must be covered by an approved
conductive service mat that has a resistance of between 50kΩ
and2MΩ, and is connected directly to a reliable earth point
via its earthing cord.

• The service personnel involved must wear a wrist-band in
direct contact with the skin, connected to the service mat.

• Printed circuit boards and other components should be placed
on the conductive service mat during installation,
maintenance etc.

Caution: If, for any reason, it is necessary to move the circuit

board or components from the conductive service mat,
they must be placed in an approved anti-static
transportation container (e.g. static shielding bag)
before transportation.

• During installation and servicing, all electrical equipment
(soldering irons, test equipment etc.) must be earthed.

16

851-165101 / Rev.A

Temperature protection

If the unit must be protected against extremes of temperature,
the carton/crate must be lined on all walls, base and lid with
5 cm thick polyurethane or polystyrene foam.

These units will be identified as delicate i n the applicable
documentation.

The package must then be clearly marked:

Note: Must not be transported or stored in temperatures

below -5 degrees Celsius.

Other units can normally be stored in temperatures
between -30° C and +70° C, refer t o the system’s technical
specifications for details.

Introduction

Transducers must not be stored in temperatures below -20°C
and above +60°C.

851-165101 / Rev.A

17

Simrad PI44

2 TRANSDUCER INSTALLATION

Purpose

Due to the fact that several transducer types may be used with
the PI44 system, you will need to read the installation manual
for the chosen transducer. The information provided in this
chapter will only provide general information. Refer to the
installation manuals provided with the transducers for more
specific information.

The PI44 can be used with maximum two transducers
simultanously, one low frequency (38 or 50 kHz) and one high
frequency (200 kHz). We recommend that any one of the
following transducers are used:

• Simrad 38-200 Combi C (dual frequency)

• Simrad 38-200 Combi D (dual frequency)

• Simrad 38-200 Combi W (dual frequency, wide beam)

Other transducers may also be used. Budget transducers
designed for leasure crafts are however not recommended for
professional fishery applications.

Topics

→ Transducer location, page 19
→ External mounting (Combi C and D), page 23
→ Blister mounting (Combi W), page 28
→ Cable glands, page 35
→ Cable in steel conduit, page 39
→ Handling and maintenance, page 40
→ Approved anti-fouling paints, page 41

Related topics

→ Purse seine hydrophone installation, page 42
→ Trawl hydrophone installation, page 79
→ Portable hydrophone, page 120

18

851-165101 / Rev.A

Transducer installation

Transducer location

General

A single answer to the question where to locate the transducer
cannot be given. It depends very much on the vessel’s
construction. However, there are some important guide lines.

Go deep

The upper water layers of the sea contain a myriad of small air
bubbles created by the breaking waves. In heavy seas the
uppermost 5 to 10 metres may be air-filled, with the highest
concentrations near the surface. Air bubbles absorb and reflect
the sound energy, and may in worst cases block the sound
transmission totally. Therefore, mount the transducer at a deep
position on the hull.

Consider the situation when the vessel is unloaded, and when it
is pitching in heavy seas. The transducer must never be lifted
free of the water surface. Not only will the sound transmission
be blocked, but the transducer may be damaged by slamming
against the sea surface.

Another reason to go deep is cavitation in front of high power
transducers. Cavitation is the formation of small bubbles in the
water due to the resulting local pressure becoming negative
during parts of the acoustic pressure cycles. The cavitation
threshold increases with the hydrostatic pressure.

Vessel heave

Heave is the up and down movement of the vessel. It disturbs
the echo traces in the echogram, so that a flat bottom is
displayed as a wave. A transducer location in the middle of the
vessel minimises the influence of vessel roll and pitch.

Noises from protruding objects on the hull

Objects protruding from the hull, such as zinc anodes, sonar
transducers or even the vessel’s keel, generate turbulence and
flow noise. Also holes and pipe outlets are noise sources. They
may act as resonant cavities amplifying the f low noise at certain
frequencies. Do not place an echo sounder transducer in the
vicinity of such objects, and especially not close behind them.

For the same reason, it is very important that the hull area
around the transducer face is as smooth and level as possible.
Even traces of sealing compound, sharp edges, protruding bolts
or bolt holes without filling compound will create noise.

851-165101 / Rev.A

19

Simrad PI44

Boundary water layer

When the vessel forces its way through the sea, the friction
between the hull and the water creates a boundary layer. The
thickness of the boundary layer depends upon vessel speed and
the roughness of the hull. Objects protruding from the hull, and
dents in the hull, disturb the flow and increase the thickness of
the boundary layer. The flow in this boundary layer may be
laminar or turbulent. A laminar flow is a nicely ordered, parallel
movement of the water. A turbulent flow has a disorderly
pattern, full of eddies. The boundary layer increases in thickness
when the flow goes from laminar to turbulent. The figure below
illustrates the boundary layer of a vessel moving through the
water.

Boundary water layers:
(A) = Turbulent flow
(B) = Laminar flow
(C) = Air bubbles in the water

Furthermore, air bubbles in the sea water are pressed down
below the hull and mixed into the boundary layer. The boundary
layer is thin underneath the forward part of the vessel, and
increases in thickness as it moves towards aft. If the sides of the
hull are steep, some of the air bubbles in the boundary layer may
escape to the sea surface along the vessel sides. It is our
experience that a wide and flat bottom, with a rising angle less
than around 13 degrees, is prone to giving air problems for the
transducer. In any case a transducer location in the forward part
of the hull is preferred in order to minimise the influence of the
boundary layer.

20

851-165101 / Rev.A

Transducer installation

Propeller noise

The propulsion propeller is the dominant noise source on most
fishing vessels, research vessels, merchant vessels and pleasure
crafts. The noise is transmitted through the sea water. For this
reason, the transducer should be placed far away from the
propeller, which means on the fore part of the hull. Positions
outside the direct line of sight from the propeller are favourable.
On small vessels with short distances it is advised to mount the
transducer on that side of the keel where the propeller blades
move upwards, because the propeller cavitation is strongest on
the other side. The cavitation starts most easily when the water
flows in the same direction as the propeller blade, and that is to
some degree the case at that side of the keel where the propeller
blades move downwards.

Bow thruster propellers are extremely noisy. When in operation,
the noise and cavitation bubbles make the echo sounder useless,
almost no matter where the transducer is installed. And when
not in operation, the tunnel creates turbulence, and if the vessel
is pitching, the tunnel may be filled with air or aerated water in
the upper position and release this in the lower position.
Therefore, an echo sounder transducer should be placed well
away from the bow thruster.

851-165101 / Rev.A

21

Simrad PI44

Summary and general recommendation

Some of the above guide lines are conflicting, and each case has
to be treated individually in order to find the best compromise.
Generally the propeller noise is the dominant factor, and a
recommended transducer location is in the fore part of the hull,
with maximum distance from the bow equal to one third of the
total length of the hull at the water line.

General recommendation for transducer location:
(A) = Transducer
(B) = Angle 1 - 2 degrees
(L) = Hull length at water line
(M) = Maximum 1/3 of the hull length at water line (L)

If the vessel hull has a bulbous bow, this may well be a good
transducer location, but also here must be taken into
consideration the flow pattern of the aerated water. Often the
foremost part of the bulb is preferable.

22

851-165101 / Rev.A

Transducer installation

External mounting

This transducer has a streamlined housing, and it is designed for
installation outside the hull.

This transducer is mainly used on smaller vessels. A location
approximately 0.5 m aside from the keel may be adequate for
the passage of water between the keel and the transducer. The
figures illustrate external mounting of transducers on steel hulls
and on wood or polyester hulls respectively.

Inclination of the transducer face

Incline the transducer face approximately 1-2 degrees (D), so
that the flowing water meets it directly. This assures laminar
water flow. Mounting screws must not be extruding from the
transducer, and the space around the screws must be filled with
a compound (C) and/or a locking ring.

Smooth surface

Ensure that the surface of the transducer face, the hull plating
and putty around the transducer is as even and smooth as
possible. Obstructions on these surfaces will create problems
with turbulant flow.

851-165101 / Rev.A

23

Simrad PI44

Steel hull

A fairing (A), made by the shipyard, is placed between the
transducer and the hull. It is required in order to adapt for the
deadrise angle of the hull, and it will also house a cable service
loop (B). The fairing can be made of wood or steel, and should
have the same outline dimensions as the transducer. Remember
to create an air outlet (E) on the fairing, and to fill the bolt holes
with a filling compound to ensure a smooth transducer surface.

24

(A) = Fairing (1) = Steel conduit
(B) = Cable service loop (2) = Stuffing tube
(C) = Filling compound (3) = Washer
(D) = 1-2 degrees inclination (4) = Rubber gasket
(E) = Air outlet (5) = Packing nipple
(F) = Forward
(I) = Threaded rod with nuts and washers, or bolt

851-165101 / Rev.A

Transducer installation

Wood or polyester hull

A fairing (A), made by the shipyard, is placed between the
transducer and the hull. It is required in order to adapt for the
deadrise angle of the hull, and will also house a cable service
loop (B). The fairing is made from wood, polyester or steel, and
should have the same outline dimensions as the transducer. Use
tarred felt (H) between th fairing and the hull. Remember to
create an air outlet (E) on the fairing, and to fill the bolt holes
with a filling compound to ensure a smooth transducer surface.

851-165101 / Rev.A

(A) = Fairing (1) = Steel conduit
(B) = Cable service loop (2) = Stuffing tube
(C) = Filling compound (3) = Washer
(D) = 1-2 degrees inclination (4) = Rubber gasket
(E) = Air outlet (5) = Packing nipple
(F) = Forward
(G) = Shim (wood)
(H) = Tarred felt
(I) = Threaded rod with nuts and washers

25

Simrad PI44

Flat hull

If the vessel’s hull is flat you do not need a fairing. The
transducer is then be bolted directly to the hull using two bronze
or stainless steel bolts (I) and a cable bushing. Note that the
cable bushing must be mounted with proper gaskets (4) under
and over the hull, as well as sealing compound (J) around the its
body. Also, fill the bolt holes with a filling compound to ensure
a smooth transducer surface.

(C) = Filling compound (3) = Washer
(F) = Forward (4) = Rubber gaskets
(I) = Threaded rod with nuts and washers
(J) = Sealing compound

26

851-165101 / Rev.A

Transducer installation

Longitudinal angle

On deplacement hulls, the transducer (A) must be mounted in an
angle of 5 to 8 degrees (B) in relation to the keel (C).

With a planing hull, this angle must be 0 degrees.

(A) = Transducer
(B)=5to8°ondeplacementhulls,0°onplaninghulls
(C) = Keel
(F) = Forward

851-165101 / Rev.A

27

Simrad PI44

Transducer blister

With a transducer with circular housing, one recommended
installation method is by using a blister.

The transducer blister must be designed and manufactured by
the installation shipyard to fit the vessel’s sixe and hull shape.

Mounting and clamping rings

Circular transducers may be provided with mounting and
clamping rings, or with drawings to allow for local production
of these. The mounting ring is welded to the hole in the
transducer blister, while the clamping ring fits around the edge
of the transducer body. Bolts through the clamping ring into the
mounting ring will then secure the transducer between them.
Note that several transducers use direction guides to allow
correct mounting.

Inclination of the transducer face

Incline the transducer face approximately 1-2 degrees, so that
the flowing water meets it directly. This assures laminar water
flow.

Smooth surface

Mounting screws or bolts must not be extruding from the
transducer blister. Ensure that the surface of the transducer face,
the blister, the hull plating and putty around the transducer is as
even and smooth as possible. Obstructions on these surfaces will
create problems with turbulant flow.

Horizontal support bar

Large diameter transducers must be fitted with a horizontal
support bar. This bar can be secured to the mounting ring using
threaded rods.

28

851-165101 / Rev.A

Transducer installation

Example: Large transducer

The illustration below shows a typical transducer blister
designed for a large transducer. Note that due to the physical
size of the transducer, a U-shaped support bar (E) is used to
support the transducer.

(A) = Streamlined blister (F) = Forward
(B) = Stiffening rib (G) = Cable service loop
(C) = Drainage holes (H) = Stuffing tube
(D) = 1-2 degrees angle (I) = Minimum 400 mm
(E) = U-shaped support bar (J) = Rounded corners

(K) = Air outlet

851-165101 / Rev.A

29

Simrad PI44

Example: Small transducer

The illustration below shows a typical transducer blister
designed for a small transducer. The same blister design
principles as for a large transducer apply.

30

(A) = Streamlined blister (E) = Air outlet
(B) = Mounting ring (F) = Forward
(C) = Clamping ring (G) = Transducer cable
(D) = Guide

Note that the transducer cable must be provided with a cable
loop inside the blister. Observe the vertical forward edge of the
blister. This will guide the water to each side of the blister.

851-165101 / Rev.A

Transducer installation

Common guidelines

The best performance is obtained with a blister height of 40 cm
or more. A streamlined shape and rounded edges reduce the
flow noise. A vertical leading edge or front will guide the
aerated water to the sides of the blister. The orientation of the
blister should follow the water flow.

The interior of the blister must be filled with sea water. Use
drainage holes in the bottom and an air outlet on the top. The
water pressure behind the transducer will then compensate for
the outside pressure during vessel movements in rough sea.

Large diameter transducers must be fitted with a horizontal
U-shaped support bar. This bar can then be secured to the
mounting ring using threaded rods.

The transducer cable penetrates the hull in a stuffing tube. Leave
an adequate loop of the cable behind the transducer for easy
mounting or removal of the transducer.

Toe-in

On a conventional hull shape, without a bulb, the front of the
blister should have a few degrees toe-in towards the bow.

(A) = Keel
(B) = Blister
(C) = Toe-in angle 5 to 8 degrees

851-165101 / Rev.A

31

Simrad PI44

Physical location

The blister is placed on one of the sides of the hull, and the
distance from the keel is a trade off between a close distance
giving a turbulent flow of water in a narrow passage, and a large
distance bringing the transducer higher up and also more
affected by vessel roll. Normally a distance of approximately
1 m is a good compromise.

Observe the horizontal and vertical distances (X and Y) between
the keel and the transducer blister. On a medium sized vessel,
the horizontal distance (X) should be approximately 1 meter.
The vertical distance (Y) must in general be as small as possible.
This is important to prevent the keel from shadowing the
transducer beam in shallow waters.

32

(A) = Keel
(B) = Transducer blister
(X) = Horizontal distance between keel and blister
(Y) = Vertical distance between the blister surface and the keel

851-165101 / Rev.A

Transducer installation

Box keel

Vessels with a box keel may use this for transducer installation.
The box keel is already the deepest part of the vessel. If the box

keel is too narrow to accommodate the transducer, it can be
widened, either symmetrically or to one side only. In the last
case the installation could also be described as a blister merged
into the keel.

Mounting and clamping rings

Circular transducers may be provided with mounting and
clamping rings, or with drawings to allow for local production
of these. The mounting ring is welded to the hole in the box
keel, while the clamping ring fits around the edge of the
transducer body. Bolts through the clamping ring into the
mounting ring will then secure the transducer between them.
Note that several transducers use direction guides to allow
correct mounting.

Inclination of the transducer face

If possible, incline the transducer face approximately 1-2
degrees, so that the flowing water meets it directly. This assures
laminar water flow.

Smooth surface

Mounting screws or bolts must not be extruding from the box
keel. Ensure that the surface of the transducer face, the box, the
hull plating and putty around the transducer is as even and
smooth as possible. Obstructions on these surfaces will create
problems with turbulant flow.

Horizontal support bar

Large diameter transducers must be fitted with a horizontal
support bar. This bar can be secured to the mounting ring using
threaded rods.

851-165101 / Rev.A

33

Simrad PI44

Example

The figure below illustrates a symmetrical box keel installation.

(A) = Box keel (D) = Cable in steel conduit
(B) = U-shaped support bar (E) = Cable service loop
(C) = Stuffing tube

34

851-165101 / Rev.A

Transducer installation

Cable glands

The transducer cable must pass through the hull using approved
cable glands for the type of vessel in question.

A steel cable gland is normally used on professional vessels
with steel hulls. A bronze cable gland can be delivered as an
option for vessels with wood or fibreglass construction. Vessel
not to be classified can as an option use a cable gland made of
plastic.

Note: Simrad strongly recommends that a length of conduit is fitted

around transducer cable glands made of steel or bronze and
extended over the water-line inside the vessel. This precaution
reduces the danger of flooding in the event of gland failure and
transducers installed in this manner are also easier to replace.

Some vessels may experience difficulties finding suitable areas
of the hull for mounting transducer cable glands due to existing
water tanks, concrete ballast or other obstacles. A possible
solution in such cases is to run the transducer cables in a steel
conduit aft along the hull until a suitable cable gland location is
available. The respective cable gland can then be installed as
described in the following instructions.

Note: Simrad takes no responsibility for the correct installation of

cable glands, associated hull modifications and/or structural
support of transducer cable penetration. These activities are
subject to individual approval by the respective classification
society for the vessel in question.

Order numbers

Steel hull cable gland kit: 599-202216
Wood/GRP hull cable gland kit: 119-038200
Small vessel cable gland kit: 599-202182

851-165101 / Rev.A

35

Simrad PI44

Cable gland installation for steel hulls

This cable gland kit is designed for steel vessels. It must be
welded to the hull plates.

(A) = Steel conduit
(B) = Stuffing tube, DNV

approved carbon steel st52.3
(C) = Washers, 24 x 8 x 2 mm
(D) = Rubber gasket
(E) = Packing nipple. Make

sure that you do not damage the
transducer cable by tightening
the packing nipple too hard!

(F) = Cable to the echo
sounder (or a junction box)

The gland gland kit includes all
of the necessary parts needed to
install the unit excluding
screws.

Simrad recommends that a one
inch steel conduit (that the
transducer cable will be run
through) with an inside
threaded diameter of
three-quarter inches is welded
to the gland’s stuffing tube. The
conduit must extend to above
the vessel’s water line.

36

851-165101 / Rev.A

Transducer installation

Gland installation for wood or GRP hulled vessels

A bronze cable gland kit is available for wood and GRP vessels.

(A) = Packing nipple. Make
sure that you do not damage the
transducer cable by tightening
the packing nipple too hard!

(B) = Washers
(C) = Rubber gaskets
(D) = Hole diameter 28 mm
(E) = Steel conduit
(F) = Cable to the echo

sounder (or a junction box)

The gland gland kit includes all
of the necessary parts needed to
install the unit excluding
screws.

Simrad recommends that a one
inch steel conduit (that the
transducer cable will be run
through) with an inside
threaded diameter of
three-quarter inches is attached
to the gland’s packing nipple.
This connection must be
watertight, and the conduit must
extend to above the vessel’s
water line.

851-165101 / Rev.A

37

Simrad PI44

Cable gland installation for smaller vessels

This cable glands made of plastic is designed for those smaller
vessels that do not need to be classified.

(A) = Packing nut (bronze).
Ensure that you do not to
damage the transducer cable by
tightening the packing nut too
hard!

(B) = Rubber gasket
(C) = Plastic disk
(D) = Rubber gasket
(E) = Stuffing tube
(F) = Backing nut (bronze)
(G) = Backing washer (plastic)
(H) = O-ring 42.5 x 3.0 N
(I) = O-ring 39.5 x 3.0 N
(J) = Cable to the echo sounder

(or a junction box)

Stuffing tube hole diameter: 36 mm ±1.5 mm.
Apply ample amount of sealant between the backing washer (H)

and the hull plate.
The cable gland kit contains all the listed parts, except the

sealant.

Note: The two O-rings must be clean, in good condition and free of cuts

or other defects which could affect their water-tight integrity.

Splicing

If you need to cut the transducer cable, you must splice it
correctly.

Note: DO NOT solder the wires together with only electrical tape for

insulation, as this will result in electrical noise and reduced
operational performance.

To splice the cable, use a metal junction box. The chassis of the
junction box must be grounded, but the cable shielding must
NOT be connected to the junction box ground.

38

851-165101 / Rev.A

Transducer installation

Cable in steel conduit

It is strongly recommended to lay a steel conduit from the
transducer’s cable gland to the echo sounder transceiver, and to
pull the transducer cable through this conduit. There are two
reasons for this.

• First, it will make it easier at a later stage to replace the
transducer.

• Second, noise and i nterference from other electrical
equipment is greatly reduced.

With a steel conduit the installation will satisfy the EU
regulations for EMC interference. Without a steel conduit, there
is a risk of reduced echo sounder performance.

The steel conduit must be unbroken and watertight from the
transducer to above the water line. From there, the cable can be
pulled further, or a junction box can be installed to facilitate
further connections. Note that the steel conduit must act as a
continuous electrical screen all the way. To ensure proper
shieklding, the conduit must be electrically connected to the
echo sounder transceiver chassis.

Steel conduit dimensions:

• minimum 35 mm inner diameter

• minimum 6 mm wall thickness (4.5 mm if galvanised).

If two or more transducers are installed close to each other it is
possible to pull their cables in the same steel conduit, provided
the conduit diameter is increased accordingly. However, for easy
replacement it is recommended that each transducer has its own
steel conduit.

851-165101 / Rev.A

39

Simrad PI44

Handling and maintenance

Do not lift the transducer by the cable.
Some transducers are delivered with a cover plate on the face

for protection during transport. Let this plate stay on as long as
possible, but do not forget to remove it before the vessel goes
into the sea.

An anti-fouling paint may be applied to the transducer face.
Because some paint types may be aggressive to the polyurethane
in the transducer face, please consult Simrad’s list of approved
paints on the next page.

Note: Arctic tanks have acoustic windows made of polycarbonate.

These must neither be painted nor cleaned with chemicals.

During dry docking of the vessel, the transducer face may be
cleaned for shells and other marine fouling. Be careful not to
make cuts in the transducer face. Use a piece of wood or a very
fine grade emery paper.

40

851-165101 / Rev.A

Transducer installation

Approved anti-fouling paints

This is Simrad’s list of approved antifouling paints on
polyurethane transducer housing.

From Jotun Paints, Sandefjord Norway:

• Antifouling Seamate HB 33

• Antifouling Seamate HB 66

• Antifouling Seamate HB 99

• Racing

• Non-stop

From International Paints:

• Intersleek tie coat + 425 FCS

- BXA386/BXA390/BXA391 Grey

- HKA563/HKA570/HKA571 Yellow

Mix BXA386, BXA390 and BXA391 first, then apply. When
dry, mix HKA563, HKA570 and HKA571, apply.

From Hempel IFA Coatings AS:

• Hempel A/F Classic 76550

From Jotun-Henry Clark Ltd:

• Anti-fouling Seaguardian

From International Marine Coatings:

• Intersmooth 360 Ecoloflex SPC

• Micron Ekstra

Note: Refer to the manufacturer’s documentation and data sheets for a

complete procedure.

851-165101 / Rev.A

41

Simrad PI44

3 PURSE SEINE HYDROPHONE

Purpose

The purpose of this chapter is to provide general guidelines for
the installation of the PI44 hydrophone for purse seining.

Note: If your vessel shall be fitted for trawl operations, DO NOT

install the hydrophone(s) as explained in this chapter!

Order numbers

Purse hydrophone, complete: HYD-202711
Purse hydrophone, without cable gland: HYD-205075

Topics

→ Precautions, page 43
→ Considerations, page 44
→ Pre-installation checklist, page 48
→ Location, page 50
→ Coverage area, orientation and tilt, page 51
→ Mounting arrangement, page 54
→ Dual hydrophones, page 57
→ Hydrophone protection, page 59
→ Hydrophone cable, page 62
→ Installation drawings, page 67

42

851-165101 / Rev.A

Purse seine hydrophone installation

Installation precautions

Caution: The following precautions must be observed. Failure to

do so can result in damage to the hydrophone which
may render the PI44 catch monitoring system
inoperative.

1 Observe the maximum allowable torque warning of 5 Nm

when tightening the hydrophone studs.

2 Use only M8x30 socket countersunk head screws for

mounting the hydrophone.

3 Secure threaded hydrophone hardware with Loctitet 270

or the equivalent.

4 Do not paint the hydrophone.
5 Do not sand-blast, power or steam wash the hydrophone.
6 Do not scrape the hydrophone with metal or other hard

objects that may damage the polyurethane sheathing.

7 Do not strike the hydrophone.
8 Do not expose the hydrophone to harsh chemicals.
9 Do not perform hot work in the vicinity of the

hydrophone.

10 Do not lift the hydrophone by its cable.

851-165101 / Rev.A

43

Simrad PI44

Considerations

Correct installation of the PI44 hydrophone is vital to the
system’s performance. Several variables must be taken into
consideration, the most important of which is the vessel’s
construction. This guide is for use in selecting the best location
for the hydrophone and includes a brief description of areas to
be avoided.

Note: Simrad strongly suggests that this information is read

thoroughly, and that the instructions are understood and
followed. Proper hydrophone placement is difficult to achieve,
but essential for correct system operation.

Depth

Water just below the sea surface contains a myriad of small air
bubbles created by the turbulence of breaking waves. The first
five to ten metres may be heavily saturated in moderate seas
with the greatest concentration and largest bubbles closest the
surface. Air bubbles disrupt sound waves in water. The degree
to which they absorb and reflect such energy vary, but in some
cases they can block hydrophone reception. It is therefore
recommended to mount the unit as deep as possible.

Pounding danger

When a vessel is in ballast and pitching in heavy seas, it is
important that the hydrophone is not lifted out of the water.
Should a vessel pound so heavily that the hydrophone be
exposed, sound reception will be interrupted and the unit may
be damaged on impact.

The boundary layer

The flow of water in the immediate vicinity of the hull of a
moving vessel is known as a boundary layer. This flow is
responsible for underwater noise that can disturb hydrophone
reception and its thickness is contingent on a vessel’s:

• Hull form

• Size and number of underwater protrusions

• Velocity

• Hull roughness

The boundary layer is thin (laminar flow) near the vessel’s bow
and becomes thicker (turbulent flow) as it moves aft. Laminar
flow is smooth with streamlines approximately parallel to the
hull and contributes relatively little to noise created by flow.
Conversely, turbulent flow is more disorderly and in turn
contributes to a greater extent.

44

851-165101 / Rev.A

Purse seine hydrophone installation

Boundary water layers:
(A) = Turbulent flow
(B) = Laminar flow
(C) = Air bubbles in the water

Air bubbles may also be introduced into the boundary layer. If
the vessel’s hull has little flare and is relatively narrow, bubbles
may escape to the sea surface without incident. On the other
hand a wide, flat hull with minimal deadrise is prone to trapping
air bubbles no matter how little flare it has. Regardless of a
vessel’s hull form, hydrophones are generally recommended to
be installed on the forward part of the hull to minimising the
influence of both turbulence and air bubbles.

Bulbous bow

The bulbous bow may be an acceptable hydrophone location.
Should this position be chosen, the foremost part of the bulb is
often best, but also the m ost susceptible to pounding.

851-165101 / Rev.A

Recommended location of the transducer on a bulbous hull:
(A) = Thruster
(B) = Hydrophone location

45

Simrad PI44

Propeller noise

A vessel’s main propeller is the dominant source of underwater
acoustic noise. When ever possible, hydrophone(s) should be
located as far a way as possible from the main propeller and
never closer than ten meters. Hydrophone(s) should not be
mounted in the direct acoustic path (line-of-sight) of the main
propeller unless absolutely necessary.

The primary cause of propeller noise is cavitation (small
bubbles generated by the partial vacuum created by the blades as
they pass through the water). The resulting underwater acoustic
noise from cavitation is normally weakest on the side of the
vessel were the propeller blades rotate toward the surface and
most pronounced on the side were they rotate toward the
bottom. Most vessels have clock-wise rotating propellers
resulting in their port sides being less effected by cavitation
induced noise than their starboard.

To minimise the negative effect of cavitation noise on
hydrophone performance, installation is generally recommended
as follows:

• Single hydrophone - if only one hydrophone is to be
installed on a vessel with a clock-wise rotating propeller, it
should be located on the port side of the hull.

• Dual hydrophones - if two hydrophones are to be installed,
they should be placed on either side of the vessel’s keel.
When in doubt about the best fore-and-aft location for
hydrophones, they can be placed at different distances from
the bow (for example the port hydrophone can be a little
further aft than the starboard, approximately three to five
meters for a thirty-five meter vessel). When trawling in both
deep and shallow water the hydrophones should also be tilted
differently with respect to each other. The hydrophone that is
closest to the propeller should have the greatest tilt and be
located on the port side of the hull for a vessels with
clock-wise rotating propellers.

Bow/sternthruster noise

46

Bow and sternthruster operation may severely effect
hydrophone reception. Hydrophone installation closer than four
meters to either is strongly discouraged.

851-165101 / Rev.A

Purse seine hydrophone installation

When not in operation, bow/sternthruster tunnels create
turbulence and hence underwater noise when a vessel is under
way. Also, as a vessel pitches in heavy weather, thruster tunnels
may fill with air or aerated water which can disturb hydrophone
reception when released. Hydrophone installation should take
into regard the noise and down stream disturbances found
around and aft of thrusters.

Note: Hydrophone installation must take into regard the noise and

down stream disturbances found around and aft of thrusters.

Noise from protruding objects and other sources

The primary sources of underwater disturbance (other than a
vessel’s main propeller and bow/sternthruster) that affect
hydrophone reception are:

• Main or bilge keels

• Zinc anodes

• Cooling elements protruding from the hull

• Equipment such as sonar hydrophones and pitot tubes

• Sea chests

• Overboard discharges

• Dents in the hull

All appendages to the hull, indentations and pipe outlets are
potential sources of underwater noise. They may act as resonant
cavities amplifying noise at certain frequencies, create cavitation
or turbulence. Hydrophones should not be located in the vicinity
of such objects and especially not immediately aft of them.

Minimum distance to sonar and echo sounder
transducers

To avoid interference, PI44 hydrophone(s) must be installed as
far away as possible from other sources of underwater acoustical
energy such as active sonars and echo sounder transducers.
Hydrophones should be placed at least two meters from such
equipment when ever possible and distances of less than one
meter avoided. Hydrophones installed in close proximity to
underwater acoustical sources should be located as far aft as
possible from them, and most importantly, not be subjected to
direct (frontal) transmission from such equipment.

Drop keel

In the event the vessel is equipped with a drop keel, the
hydrophones should be mounted aft of it. The choice between
installing a one, or two hydrophone system should be based on
the same horizontal and vertical coverage requirements for
vessels operating under similar conditions with fixed keels.

851-165101 / Rev.A

47

Simrad PI44

Pre-installation check-list

Choosing the optimal locations for hydrophones is not always
easy, but decisions made at this phase of the installation process
are critical to future system performance. Determining the best
configuration for a given vessel often involves a compromise
between contradicting requirements.

To aid in this evaluation process Simrad recommends that this
installation manual be read thoroughly and the following check
list completed before deciding on a final installation strategy for
the PI44 system.

1 Hydrophones do not have a direct line-of-sight to the main

propeller and are placed where the vessel’s hull protects
them from underwater acoustic noise as well as possible.

2 Hydrophones must always have an unobstructed

line-of-sight to the sensors attached to the gear for the
system to operate properly.

3 The distance from the main propeller to the hydrophones

should be greater than ten meters. A separation of less
than ten meters can reduce system range significantly.

4 If thrusters are installed, hydrophones should be located at

least four meters from them.

5 Avoid locating hydrophones behind thrusters where air

bubbles from their tunnels generated when the vessel
pounds can block sensor signals.

6 Hydrophone should not be placed forward of other

underwater acoustic equipment and preferably behind it as
far away as possible, distances of less than one meter
should be avoided.

7 There should never be possible sources of underwater

acoustic noise placed in front of hydrophones.

8 Remember that hydrophones are to be mounted with their

long axis up (in the vertical plane).

9 Hydrophones installed in blisters should be located away

from the vessel’s keel and as deep as possible on the hull.

10 Hydrophones installed in shoes along the vessel’s keel

should be mounted as deeply as possible.

48

11 Hydrophone cables that are run in conduit along the

outside of the vessels hull should be arranged as to
produce the least amount of underwater acoustic noise as
possible.

12 Blisters and shoes should be as streamlined as possible and

have all of their corners rounded to minimize the
generation of underwater acoustic noise.

851-165101 / Rev.A

Purse seine hydrophone installation

13 Conduit used to run hydrophone cables in the interior of a

vessel’s hull should extend well over its water line.

14 If you install both trawl and purse seine hydrophones, do

not confuse the two types. The Trawl hydrophones are
marked with order number 314-205250, while the Purse
seine hydrophones are marked with order number

314-202275.

15 Other well-founded information or experience regarding

hydrophone installation be available should also be
evaluated even though not directly mentioned in these
instructions.

851-165101 / Rev.A

49

Simrad PI44

Optimal location of purse seine
hydrophones

The most influential factors effecting hydrophone reception
common to most vessels are:

• Noise from cavitation generated by the main propeller.

• Air bubbles in the water around the hydrophone which

impede acoustic signals.

• Noise from other acoustic equipment mounted in close
proximity.

Taking these main sources of disturbance into consideration, the
generally recommended location for mounting a single
hydrophone is approximately one third the vessel’s water-line
length from the bow.

Installations requiring the use of two hydrophones may position
the first as described above and the second forward of the bow
thruster in conjunction with the transducer shoe for the echo
sounder. Both hydrophones must be located at least four meters
from the bow thruster.

Optimal hydrophone placement differs from vessel to vessel.
Variables effecting hydrophone performance must be understood
so that the best location may be chosen given a vessel’s design
and particular operation.

The illustration shows the recommended fore (B) and aft (A)
locations for single hydrophone locations. For a dual
installation, both are used. (L) is the total length of the hull
measur ed at the waterline.

50

851-165101 / Rev.A

Purse seine hydrophone installation

Coverage area, orientation and tilt

General

Once the fore and aft placement of the purse seine hydrophone
is decided, it is equally important to carefully consider its
horizontal and vertical orientation. Hydrophone orientation can
have a large influence on system performance.

The hydrophone’s beam sensitivity is concentrated within a 90_
horizontal and -30_ vertical sector. Both keel and hull
installations are to be located on the side of the vessel that the
seine is shot.

Note: These installation instructions and related drawings are for

vessels shooting and pursing to STARBOARD.

Horizontal cove rage area

When the seine is normally located forward of the starboard
beam when pursing the following information should be taken
into consideration:

1 When the seine is pursed in the sector from approximately

000_ to 120_ relative to the bow, the hydrophone should
be installed at an angle of 70_ to the vessels centre line.

2 When the seine is pursed in the sector from approximately

030_ to 150_relative to the bow, the hydrophone should
be installed at an angle of 90_ to the vessel’s centre line.

The most important elements with regard to the horizontal
coverage area of the hydrophone are:

1 An unobstructed line-of-sight to the PI44 sensor(s)

attached to the purse seine.

2 The hydrophone is directed at the middle of the net when

pursing.

3 Two hydrophones may be used for applications requiring a

large coverage area.

851-165101 / Rev.A

51

Simrad PI44

Figure 1 Horizontal
coverage area

The illustration shows a hydrophone installed at an angle of 70
degrees to the vessel’s center line.

(A) = The PI44 hydrophone
(B) = The horizontal coverage area

Vertical coverage area

The hydrophone has a vertical beam width of -30_ and should
be tilted so that the most important part of the seine is
adequately covered. Tilt should be no less than -15_ in most
instances with the optimal tilt angle depending on the size
(length/depth) of the seine in use. Heeling of the vessel after the
seine is set must also be taken into consideration. For a large
purse seine (about 1000m or longer) the recommend a tilt angle
is -15_ plus the estimated angle of heel when the net is set. For
smaller and deeper seines it may be necessary to increase the tilt
angle.

52

851-165101 / Rev.A

Tilt angle

The tilt angle is a function of net length and depth and may be
estimated as follows:

α = - [arctan (depth/length*π)-15_+β]

α = tilt angle
β=angle of heel (to port) after deploying the purse seine to

starboard
The following table gives some examples of recommended tilt

angles for common size pure seines:

Recommended tilt angles

Purse seine hydrophone installation

Net length/depth
in meters

Recommended
tilt angle *

*The tilt angle should be increased accordingly if the vessel heels after the seine is shot. Tilt
angles of less than --15_ are not recommended.

250 / 50 350 / 100 650 / 150 850 / 180 1500 / 200 2000 / 200

-- 1 5 _ -- 2 5 _ -- 2 0 _ -- 2 0 _ -- 1 5 _ -- 1 5 _

851-165101 / Rev.A

53

Simrad PI44

Mounting arrangement

The PI44 purse hydrophone are delivered ready for installation
in either freestanding or keel mounted shoes (which are to be
built by the shipyard responsible for the installation). Several
alternatives with corresponding detailed drawings have been
included in this manual to cover the majority of installation
options available. Information regarding through-hull
penetration is also described to compliment the rules and
regulations of the respective vessel’s classification society.

Referenced drawings

→ PI44 Purse hydrophone, outline dimensions, page 68
→ PI44 Purse hydrophone, cutout, page 69
→ Purse hydrophone, keel mounted, steel or aluminum, page 70
→ Purse hydrophone, keel mounted, sandwich or wood, page 73
→ Purse hydrophone, blister installation, page 76

54

851-165101 / Rev.A

Purse seine hydrophone installation

Keel mounted shoes

The hydrophone shoe may be keel mounted to avoid creating an
appendage to the hull which may foul the purse wire.

Keel mounted hydrophone shoe:
(A) = Tilt angel
(B) = Vertical coverage area
(C) = Keel mounted hydrophone with
fairing

Should this solution be chosen, the
following must be taken into
consideration:

• The hydrophone must have an
unobstructed line-of-sight to the PI44
sensor(s) attached to the seine.

• The centre of the hydrophone’s beam
must be directed as much as possible
toward the bottom of the net where
the PI44 sensors are located. The tilt
angle must be increased with regard
to the expected heel of the vessel.

• For a short and deep seine a tilt angle (A) of 20_ to 25_ is
recommended. For a short and shallow or large seine a 15_
tilt angle may be best.

• If monitoring of the headline under pursing is desired the
hydrophone should not be tilted more than 15_.

• The hydrophone shoe must be mounted as deep as possible
on the keel, but not so deep that it may be damaged while
docking.

• The hydrophone shoe must be streamlined to avoid creating
turbulence and underwater noise.

• For applications that require extensive coverage, regardless
of net size, several hydrophones may be installed with
different tilt angles.

851-165101 / Rev.A

55

Simrad PI44

Free standing hydrophone in blister

If there is no risk that hull protrusions will be fouled by the
purse wire, mounting the hydrophone in a freestanding blister is
a viable option.

Free standing hydrophone in blister:
(A) = Tilt angel
(B) = Vertical coverage area
(C) = Free standing hydrophone in
blister (pipe diameter 200 to 250 mm)
(1) = Approximately 400 mm, minimum
250 mm is required
(2) = Must exceed 700 mm.

Should this solution be chosen, the
following must be taken into
consideration:

• The centre of the hydrophone’s beam
must be directed as much as possible
toward the bottom of the net where
the PI44 sensor(s) are located. The tilt
angle should be increased with regard
to the expected heel of the vessel.

• For a short and deep seine a tilt angle (A) of 20_ to 25_ is
recommended. For a short and shallow or large seine a 15_
tilt angle may be best.

• If monitoring of the headline under pursing is desired the
hydrophone should not be tilted more than 15_.

• For applications that require extensive coverage, regardless
of net size, several hydrophones may be installed with
different tilt angles.

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851-165101 / Rev.A

Purse seine hydrophone installation

Dual hydrophone installation

Large vessels and operations requiring a greater than normal
coverage area can install two hydrophones with a vertical and
horizontal overlap. Hydrophone selection is made with the help
of a switch located in the wheelhouse.

To reduce the possibility of interference from air bubbles and
underwater noise when reversing propulsion or using thrusters
the two hydrophones should be located at least five meters from
each other in the fore and aft plane. It is also recommended to
install the two hydrophones with a slightly different tilt angles
so that a larger vertical sector may be covered. Vessels equipped
with a bowthruster or bulbous bow can install the first
hydrophone forward of the bowthruster on the bulbous bow and
the second aft of the bowthruster. Dual hydrophone installations
may be either keel mounted or installed in free-standing blisters.

Horizontal cove rage areas

When the seine is normally located forward of the starboard
beam when pursing the following information should be taken
into consideration:

• When the seine is pursed in the sector from approximately
000_ to about 130_ relative to the bow, the foremost
hydrophone should be installed at an angle of 50_ and the
after 90_ to the vessel’s centre line.

• Should special circumstances require coverage outside the
standard 000_ to 130_ sector the hydrophones may be
installed accordingly.

851-165101 / Rev.A

(A) = Aft hydrophone, (B) = Forward hydrophone
(C) and (D) = Horizontal coverage areas

57

Simrad PI44

Vertical coverage areas

When the seine is normally located forward of the starboard
beam when pursing the following information should be taken
into consideration:

• The optimal tilt angle for dual
hydrophone installations is
derived in the same manner as a
for single hydrophone
installations. Consult the
section on Tilt angle for more
information.

• The hydrophones should be
tilted so that the most important
part of the seine is adequately
covered. Tilting the forward
hydrophone -25_ and the after

-15_ will provide proper
coverage in most instances.

• Tilt should be no less than -15_ in most instances with the
optimal tilt angle depending on the size (length/depth) of the
seine in use.

• Heeling of the vessel after the seine is set must be taken into
consideration when calculating the tilt angle.

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851-165101 / Rev.A

Purse seine hydrophone installation

Hydrophone protection

Warning: Do not perform hot work near, paint, scrape, hit,

pry, force, sandblast, high-pressure wash or
otherwise subject hydrophones to excessive
force.

Installation precautions

The following precautions must be observed. Failure to do so
can result in damage to the purse seine hydrophone which may
render the PI44 system inoperative.

1 Do not install the hydrophone until all hot work is

complete!

2 Do not over-tighten the packing nipple as this could

damage the hydrophone’s cable!

3 Observe the maximum allowable torque warning of 5 Nm

when tightening hydrophone studs!

4 Use only stainless steel M8x35 socket countersunk head

screws for mounting the hydrophone!

5 Secure threaded hydrophone hardware with Loctitet 270

or the equivalent!

6 The PI44 cabinet should always be connected to the ship’s

ground to reduce the effects of electrical interference on
the system!

Under installation

Hydrophones must not be installed until all structural work,
specifically welding sandblasting and other potentially harmful
operations are completed. If hot work, sandblasting, spay
painting or water blasting is to be performed in the vicinity of a
hydrophone it must be properly protected. PI44 hydrophones
although very rugged, contain sensitive ceramic elements and
electronic circuits and therefore should never be struck, prided,
clamped or subject to other types of potentially damaging force
as for example over-tightening mounting hardware.

851-165101 / Rev.A

Deflection plates

Simrad recommends that hydrophones mounted in blisters be
protected by rope deflections plates both forward and aft. Such
precautions will help protect the hydrophones, especially in the
event the vessel passes over a wire, line or net.

59

Simrad PI44

Vessels operation in colder climates should weld steel fins and
protection plates installed around hydrophones to protect them
from being damaged by ice. Detailed drawing must be made
specifically to suite each individual vessel in question and the
installation performed by an authority with the expertise to do
so.

Surface protection

Maintenance and replacement costs can be reduced if those parts
of the hydrophone installation that are open to the sea are
protected correctly. Any new metal or original plating involved
in the hydrophone installation which has been cut, sand-blasted,
welded or otherwise had its protective coating compromised
must be thoroughly cleaned and repainted. For steel vessels use
polyester primer, undercoat and top-coat according to the
manufacture’s instructions, then apply the same anti-fouling
paint used on the rest of the hull.

Hydrophone face

This is Simrad’s list of approved antifouling paints for
hydrophone faces.

From Jotun Paints, Sandefjord Norway:

• Antifouling Seamate HB 33, HB 66 and HB 99

• Racing

• Non-stop

From International Paints:

• Intersleek tie coat + 425 FCS

- BXA386/BXA390/BXA391 Grey

- HKA563/HKA570/HKA571 Yellow

Mix BXA386, BXA390 and BXA391 first, then apply. When
dry, mix HKA563, HKA570 and HKA571, apply.

From Hempel IFA Coatings AS:

• Hempel A/F Classic 76550

From Jotun-Henry Clark Ltd:

• Anti-fouling Seaguardian

From International Marine Coatings:

• Intersmooth 360 Ecoloflex SPC

• Micron Ekstra

Note: Refer to the manufacturer’s documentation and data sheets for a

complete procedure.

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Purse seine hydrophone installation

Location and marking

After installation, the location of hydrophones should be clearly
marked on the vessel’s hull (above the water-line) directly over
them. This information will help prevent hydrophone damage
when dry-docking the vessel. It is very important to amend the
docking-plans of larger vessels to also reflect this information so
that blocks will not be placed in the vicinity of hydrophones,
fins, deflection plates or other associated appendages.

After installation / Sea trials

Once the installation is complete and the vessel afloat, the
system’s performance should be documented. Refer to the
appropriate section in the PI44 Operation manual regarding the
measurement of a noise vs. speed curve.

851-165101 / Rev.A

61

Simrad PI44

Hydrophone cable

The purse seine hydrophone is delivered with a 22 m cable. The
cable is fitted with plug that fits the ANT socket on the rear side
of the PI44 Operator Unit.

General cable gland guidelines

Hydrophone cables are passed through the hull using approved
cable glands for the type of vessel in question. The standard
delivery consists of a steel cable gland that is to be welded to
the hull.

A bronze cable gland can be delivered as an option for vessels
with wood or fibreglass construction. Vessel not to be classified
can as an option use a cable gland made of plastic.

Note: Simrad strongly recommends that a length of conduit be fitted

around hydrophone cable glands made of steel or bronze and
extended over the water-line inside the vessel. This precaution
reduces the danger of flooding in the event of gland failure and
hydrophones installed in this manner are also easier to replace.

Some vessels may experience difficulties finding suitable areas
of the hull for mounting hydrophone cable glands due to
existing water tanks, concrete ballast or other obstacles. A
possible solution in such cases is to run the hydrophone cables
in a steel conduit aft along the hull until a suitable cable gland
location is available. The respective cable gland can then be
installed as described in the following instructions.

Note: Simrad takes no responsibility for the correct installation of

cable glands, associated hull modifications and/or structural
support of hydrophone cable penetration. These activities are
subject to individual approval by the respective classification
society for the vessel in question.

Order numbers

Steel hull cable gland kit: 599-202216
Wood/GRP hull cable gland kit: 119-038200
Small vessel cable gland kit: 599-202182

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Purse seine hydrophone installation

Cable gland installation for steel hulls

The cable gland kit for steel vessels is included with standard
deliveries. The drawing shows a single hydrophone, but
normally a typical installation includes two hydrophones with
respective cables spliced in a junction box and run to the
wheelhouse in a conduit.

Cable gland for steel hull
vessels.

(A) = Steel conduit
(B) = Stuffing tube, DNV

approved carbon steel st52.3
(C) = Washers, 24 x 8 x 2 mm
(D) = Rubber gasket
(E) = Packing nipple. Make

sure that you do not damage the
hydrophone cable by tightening
the packing nipple too hard!

(F) = Cable to the PI Operator
unit (or a junction box)

The gland gland kit includes all
of the necessary parts needed to
install the unit excluding
screws.

851-165101 / Rev.A

63

Simrad PI44

Gland installation for wood or GRP hulled vessels

A bronze cable gland kit is available for wood and GRP vessels.
This kit is not included in the standard delivery, and must be
ordered separately .

The drawing shows a single hydrophone, but normally a typical
installation includes two hydrophones with respective cables
spliced in a junction box and run to the wheelhouse in a conduit.

Cable gland for wood and GRP
hulls.

(A) = Packing nipple. Make
sure that you do not damage the
hydrophone cable by tightening
the packing nipple too hard!

(B) = Washers
(C) = Rubber gaskets
(D) = Hole diameter 28 mm
(E) = Steel conduit
(F) = Hydrophone cable

The gland gland kit includes all
of the necessary parts needed to
install the unit excluding
screws.

Simrad recommends that a one inch conduit (that the
hydrophone cable will be run through) with an inside threaded
diameter of three-quarter inches be attached to the gland’s
packing nipple. This connection must be watertight, and the
conduit must extend to over the vessel’s water line and
terminated as described for steel hulled vessels.

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Purse seine hydrophone installation

Cable gland installation for smaller vessels

Cable glands made of plastic for those smaller vessels that do
njot need to be classified are optional equipment for standard
deliveries. This cable gland kit is not included in the standard
delivery, and must be ordered separately.

The drawing shows a single hydrophone, but normally a typical
installation includes two hydrophones with respective cables
spliced in a junction box and run to the wheelhouse in a conduit.

Hydrophone cable gland for
small vessels.

(A) = Packing nut (bronze).
Ensure that you do not to
damage the hydrophone cable
by tightening the packing nut
too hard!

(B) = Rubber gasket
(C) = Plastic disk
(D) = Rubber gasket
(E) = Stuffing tube
(F) = Backing nut (bronze)
(G) = Backing washer (plastic)
(H) = O-ring 42.5 x 3.0 N
(I) = O-ring 39.5 x 3.0 N
(J) = Hydrophone cable

Stuffing tube hole diameter: 36 mm ±1.5 mm.
Apply ample amount of sealant between the backing washer (H)

and the hull plate.
The cable gland kit contains all the listed parts, except the

sealant.

Note: The two O-rings must be clean, in good condition and free of cuts

or other defects which could affect their water-tight integrity.

851-165101 / Rev.A

65

Simrad PI44

Splicing

If you need to cut the cable, you must splice it correctly.

Note: DO NOT solder the wires together with only electrical tape for

insulation, as this will result in electrical noise and reduced
operational performance.

To splice the cable, use a metal junction box. The chassis of the
junction box must be grounded, but the cable shielding must
NOT be connected to the junction box ground.

Note: Make sure that you connect the cables 1:1! The red cable in the

“input” cable MUST be connected to the red cable in the
“output” cable etc.

Cable specification

If extension cables are used, these must be supplied by the
installation shipyard. The following specifications must be
regarded as a minimum:

2x2x0.5mm

2

/ Twisted pairs / Overall braided

Observe the information regarding cable splicing.

Grounding and shielding

Cable shielding must be continuous. The shielding is terminated
in the cabinet and must not be grounded in the junction boxes.

In order to minimize electrical interference, Simrad strongly
recommends that the hydrophone cable is installed in a metal
conduit between the hydrophone and the PI44 cabinet.

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Purse seine hydrophone installation

Installation drawings

Observe the following drawings. The drawings are also
available on electronic format (DWG or PDF), consult your
local dealer.

→ PI44 Purse hydrophone, outline dimensions, page 68
→ PI44 Purse hydrophone, cutout, page 69
→ Purse hydrophone, keel mounted, steel or aluminum, page 70
→ Purse hydrophone, keel mounted, sandwich or wood, page 73
→ Purse hydrophone, blister installation, page 76

851-165101 / Rev.A

67

Simrad PI44

68

PI44 Purse Seine hydrophone - Outline dimensions

851-165101 / Rev.A

Purse seine hydrophone installation

851-165101 / Rev.A

PI44 Purse Seine hydrophone - Cutout

69

Simrad PI44

PI44 Purse Seine hydrophone - Keel mounted hydrophone, steel hull - Page 1

70

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Purse seine hydrophone installation

PI44 Purse Seine hydrophone - Keel mounted hydrophone, steel hull - Page 2

851-165101 / Rev.A

71

Simrad PI44

PI44 Purse Seine hydrophone - Keel mounted hydrophone, steel hull - Page 3

72

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Purse seine hydrophone installation

PI44 Purse Seine hydrophone - Keel mounted hydrophone, wooden hull - Page 1

851-165101 / Rev.A

73

Simrad PI44

PI44 Purse Seine hydrophone - Keel mounted hydrophone, wooden hull - Page 2

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PI44 Purse Seine hydrophone - Keel mounted hydrophone, wooden hull - Page 3

851-165101 / Rev.A

75

Simrad PI44

76

PI44 Purse Seine hydrophone - blister installation on steel hull - Page 1

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Purse seine hydrophone installation

PI44 Purse Seine hydrophone - blister installation on steel hull - Page 2

851-165101 / Rev.A

77

Simrad PI44

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PI44 Purse Seine hydrophone - blister installation on steel hull - Page 3

851-165101 / Rev.A

Trawl hydrophone installation

4 TRAWL HYDROPHONE

Purpose

The purpose of this chapter is to provide general guidelines for
the installation of the PI44 hydrophone for trawl..

Note: If your vessel shall be fitted for purse seine operations, DO NOT

install the hydrophone(s) as explained in this chapter!

Order numbers

Trawl hydrophone, complete: HYD-205254
Trawl hydrophone, without cable gland: HYD-205826

Topics

→ Precautions, page 80
→ Considerations, page 81
→ Pre-installation checklist, page 86
→ Location, page 88
→ Coverage area, orientation and tilt, page 91
→ Mounting arrangement, page 95
→ Dual hydrophones, page 101
→ Hydrophone protection, page 102
→ Hydrophone cable, page 105
→ Installation drawings, page 110

851-165101 / Rev.A

79

Simrad PI44

Installation precautions

Caution: The following precautions must be observed. Failure to

do so can result in damage to the hydrophone which
may render the PI44 catch monitoring system
inoperative.

1 Observe the maximum allowable torque warning of 5 Nm

when tightening the hydrophone studs.

2 Use only M8x30 socket countersunk head screws for

mounting the hydrophone.

3 Secure threaded hydrophone hardware with Loctitet 270

or the equivalent.

4 Do not paint the hydrophone.
5 Do not sand-blast, power or steam wash the hydrophone.
6 Do not scrape the hydrophone with metal or other hard

objects that may damage the polyurethane sheathing.

7 Do not strike the hydrophone.
8 Do not expose the hydrophone to harsh chemicals.
9 Do not perform hot work in the vicinity of the

hydrophone.

10 Do not lift the hydrophone by its cable.

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Trawl hydrophone installation

Considerations

Correct installation of PI44 hydrophone(s) is vital to system
performance. Several variables must be taken into consideration,
the most important of which is the vessel’s construction. This
guide is for use in selecting the best location for the hydrophone
and includes a brief description of areas to be avoided.

Note: Simrad strongly suggests that this information is read

thoroughly, and that the instructions are understood and
followed. Proper hydrophone placement is difficult to achieve,
but essential for correct system operation.

Depth

Water just below the sea surface contains a myriad of small air
bubbles created by the turbulence of breaking waves. The first
five to ten metres may be heavily saturated in moderate seas
with the greatest concentration and largest bubbles closest the
surface. Air bubbles disrupt sound waves in water. The degree
to which they absorb and reflect such energy vary, but in some
cases they can block hydrophone reception. It is therefore
recommended to mount the unit as deep as possible.

Pounding danger

When a vessel is in ballast and pitching in heavy seas, it is
important that the hydrophone is not lifted out of the water.
Should a vessel pound so heavily that the hydrophone be
exposed, sound reception will be interrupted and the unit may
be damaged on impact.

The boundary layer

The flow of water in the immediate vicinity of the hull of a
moving vessel is known as a boundary layer. This flow is
responsible for underwater noise that can disturb hydrophone
reception and its thickness is contingent on a vessel’s:

• Hull form

• Size and number of underwater protrusions

• Velocity

• Hull roughness

The boundary layer is thin (laminar flow) near the vessel’s bow
and becomes thicker (turbulent flow) as it moves aft. Laminar
flow is smooth with streamlines approximately parallel to the
hull and contributes relatively little to noise created by flow.
Conversely, turbulent flow is more disorderly and in turn
contributes to a greater extent.

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Simrad PI44

Boundary water layers:
(A) = Turbulent flow
(B) = Laminar flow
(C) = Air bubbles in the water

Air bubbles may also be introduced into the boundary layer. If
the vessel’s hull has little flare and is relatively narrow, bubbles
may escape to the sea surface without incident. On the other
hand a wide, flat hull with minimal deadrise is prone to trapping
air bubbles no matter how little flare it has. Regardless of a
vessel’s hull form, hydrophones are generally recommended to
be installed on the forward part of the hull to minimising the
influence of both turbulence and air bubbles.

Bulbous bow

The bulbous bow may be an acceptable hydrophone location.
Should this position be chosen, the foremost part of the bulb is
often best, but also the m ost susceptible to pounding.

Figure 2 Transducer
location on a bulbous
bow

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Propeller noise

A vessel’s main propeller is the dominant source of underwater
acoustic noise. When ever possible, hydrophone(s) should be
located as far a way as possible from the main propeller and
never closer than ten meters. Hydrophone(s) should not be
mounted in the direct acoustic path (line-of-sight) of the main
propeller unless absolutely necessary.

The primary cause of propeller noise is cavitation (small
bubbles generated by the partial vacuum created by the blades as
they pass through the water). The resulting underwater acoustic
noise from cavitation is normally weakest on the side of the
vessel were the propeller blades rotate toward the surface and
most pronounced on the side were they rotate toward the
bottom. Most vessels have clock-wise rotating propellers
resulting in their port sides being less effected by cavitation
induced noise than their starboard.

To minimise the negative effect of cavitation noise on
hydrophone performance, installation is generally recommended
as follows:

• Single hydrophone - if only one hydrophone is to be

installed on a vessel with a clock-wise rotating propeller, it
should be located on the port side of the hull.

• Dual hydrophones - if two hydrophones are to be installed,

they should be placed on either side of the vessel’s keel.
When in doubt about the best fore-and-aft location for
hydrophones, they can be placed at different distances from
the bow (for example the port hydrophone can be a little
further aft than the starboard, approximately three to five
meters for a thirty-five meter vessel). When trawling in both
deep and shallow water the hydrophones should also be tilted
differently with respect to each other. The hydrophone that is
closest to the propeller should have the greatest tilt and be
located on the port side of the hull for a vessels with
clock-wise rotating propellers.

Bow/sternthruster noise

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Bow and sternthruster operation may severely effect
hydrophone reception. Hydrophone installation closer than four
meters to either is strongly discouraged.

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Simrad PI44

When not in operation, bow/sternthruster tunnels create
turbulence and hence underwater noise when a vessel is under
way. Also, as a vessel pitches in heavy weather, thruster tunnels
may fill with air or aerated water which can disturb hydrophone
reception when released. Hydrophone installation should take
into regard the noise and down stream disturbances found
around and aft of thrusters.

Note: Hydrophone installation must take into regard the noise and

down stream disturbances found around and aft of thrusters.

Noise from protruding objects and other sources

The primary sources of underwater disturbance (other than a
vessel’s main propeller and bow/sternthruster) that affect
hydrophone reception are:

• Main or bilge keels

• Zinc anodes

• Cooling elements protruding from the hull

• Equipment such as sonar hydrophones and pitot tubes

• Sea chests

• Overboard discharges

• Dents in the hull

All appendages to the hull, indentations and pipe outlets are
potential sources of underwater noise. They may act as resonant
cavities amplifying noise at certain frequencies, create cavitation
or turbulence. Hydrophones should not be located in the vicinity
of such objects and especially not immediately aft of them.

Minimum distance to sonar and echo sounder
transducers

To avoid interference, PI44 hydrophone(s) must be installed as
far away as possible from other sources of underwater acoustical
energy such as active sonars and echo sounder transducers.
Hydrophones should be placed at least two meters from such
equipment when ever possible and distances of less than one
meter avoided. Hydrophones installed in close proximity to
underwater acoustical sources should be located as far aft as
possible from them, and most importantly, not be subjected to
direct (frontal) transmission from such equipment.

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Drop keel

In the event the vessel is equipped with a drop keel, the
hydrophones should be mounted aft of it. The choice between
installing a one, or two hydrophone system should be based on
the same horizontal and vertical coverage requirements for
vessels operating under similar conditions with fixed keels.

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Simrad PI44

Pre-installation check-list

Choosing the optimal locations for hydrophones is not always
easy, but decisions made at this phase of the installation process
are critical to future system performance. Determining the best
configuration for a given vessel often involves a compromise
between contradicting requirements.

To aid in this evaluation process Simrad recommends that this
installation manual be read thoroughly and the following check
list completed before deciding on a final installation strategy for
the PI44 system.

1 Hydrophones do not have a direct line-of-sight to the main

propeller and are placed where the vessel’s hull protects
them from underwater acoustic noise as well as possible.

2 Hydrophones must always have an unobstructed

line-of-sight to the sensors attached to the gear for the
system to operate properly.

3 The distance from the main propeller to the hydrophones

should be greater than ten meters. A separation of less
than ten meters can reduce system range significantly.

4 If thrusters are installed, hydrophones should be located at

least four meters from them.

5 Avoid locating hydrophones behind thrusters where air

bubbles from their tunnels generated when the vessel
pounds can block sensor signals.

6 Hydrophone should not be placed forward of other

underwater acoustic equipment and preferably behind it as
far away as possible, distances of less than one meter
should be avoided.

7 There should never be possible sources of underwater

acoustic noise placed in front of hydrophones.

8 Hydrophones should be offset twenty degrees from the

vessel’s centre line for normal single boat trawling. This
provides a ten degree overlap and a coverage area of
ninety degrees aft. Refer to the corresponding sections of
this manual for more information.

86

9 If there is any doubt about the best fore-and-aft location,

the port hydrophone can be placed a little farther aft (three
to five meters) in relation to the starboard. Hydrophones
can be tilted at slightly different angles when operating in
both deep and shallow waters. Refer to the corresponding
sections of this manual for more information.

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Trawl hydrophone installation

10 The hydrophone that is closest to the main propeller

should be located on the port side of the vessel and have
the greatest tilt.

11 If both hydrophone are located equally distant from the

main propeller, but are tilted differently, the starboard
hydrophone should be tilted the most because underwater
acoustic noise is more prevalent on that side of the vessel.

12 Locating hydrophones at the after end of a bulbous bow

can produce good results. Previously installed sonars in
this area that can subject hydrophones to direct signals
will produce interference.

13 Hydrophone can also be mounted in the after end of echo

sounder shoes as long as the minimum required distances
and orientation with regard to other underwater acoustic
equipment is observed.

14 Remember that hydrophones are to be mounted with their

long axis up (in the vertical plane).

15 Hydrophones installed in blisters should be located away

from the vessel’s keel and as deep as possible on the hull.

16 Hydrophones installed in shoes along the vessel’s keel

should be mounted as deeply as possible.

17 Hydrophone cables that are run in conduit along the

outside of the vessels hull should be arranged as to
produce the least amount of underwater acoustic noise as
possible.

18 Blisters and shoes should be as streamlined as possible and

have all of their corners rounded to minimize the
generation of underwater acoustic noise.

19 Conduit used to run hydrophone cables in the interior of a

vessel’s hull should extend well over its water line.

20 If you install both trawl and purse seine hydrophones, do

not confuse the two types. The Trawl hydrophones are
marked with order number 314-205250, while the Purse
seine hydrophones are marked with order number

314-202275.

21 Other well-founded information or experience regarding

hydrophone installation be available should also be
evaluated even though not directly mentioned in these
instructions.

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Simrad PI44

Optimal location of trawl hydrophones

The most influential factors effecting hydrophone reception
common to most vessels are:

• Noise from cavitation generated by the main propeller.

• Air bubbles in the water around the hydrophone which

impede acoustic signals.

• Noise from other acoustic equipment mounted in close

proximity.

If the shipyard or persons responsible for placement and
mounting the hydrophone(s) have knowledge and the proper
experience with installation of similar equipment, it should be
fully exploited when deciding where to locate the hydrophones.
This also holds true for adjusting the degree to which a
hydrophone should be tilted with regard to the both the vessel’s
physical characteristics and fishing method. Proper hydrophone
installation can increase overall system performance more than
any other single factor and therefore it is important that all the
variables involved be understood and taken into account. Often,
individual hydrophone installation requirements contradict one
an other and only an in-depth knowledge of the principles
involved can aid in deciding which should be given priority.

General rules-of-thumb

Although individual vessel vary greatly with regard to physical
construction and fishing methods, the following rules of thumb
apply under most circumstances.

• Hydrophones should be located as far forward as possible,

normally one-third the length of the water-line from the bow.

• If a vessel has a bow thruster, bubbles generated by its tunnel

can block sensor signals. Hydrophones therefore should be
either located forward of bow thrusters or far aft out of the
stream of bubbles found behind them. Vessels equipped with
bulbous bows can mount hydrophones in a specially designed
shoe on the after part of the bulb, forward of the bow
thruster.

• The minimum distance a hydrophone should be located from

the main propeller is ten meters. Systems with hydrophones
mounted closer than this will have reduced range due to
underwater acoustic noise generated by propeller cavitation.

• For trawlers that do not have to take a pursing wire into

consideration, hydrophones can be mounted in specially
constructed blisters offset from the vessel’s keel (preferably
1200 mm, but no less than 700 mm) to avoid turbulence. To

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also aid in reducing the effects of turbulence, hydrophones
should be installed as deeply as possible (preferably 600 mm,
but not less than 400 mm) from the vessel’s outer hull. When
ever possible, the distance from the keel to the bottom of the
hydrophone blister should not exceed 50 mm which can be
adjusted by countersinking the installation.

• Keel installation of hydrophones is recommended for

combined trawl/purse seining vessels that can not have
blisters projecting from their hulls.

On the starboard side of such vessels a purse seine
hydrophone can be installed together with a trawl
hydrophone.

• Hydrophones should have and unobstructed “view” of the

sensors attached to the gear, but not be located in the
line-of-sight of the main propeller.

• Hydrophones should be located aft of echo sounder

transducers or sonar installations, preferable at a distance of
two meters or more. A proximity of less than one meter
should be avoided and hydrophones should never be subject
to their direct (frontal) transmission.

• Objects protruding from the hull will generate noise, the

areas aft of which should not be used to mount hydrophones.

• Thruster tunnels generate air bubbles which disrupt signals

from the sensors. The areas aft of thruster tunnels or other
sunken areas of the hull should not be used to mount
hydrophones.

• If there is any doubt about the fore-and-aft positions for the

hydrophones, they should be located at different distances
from the bow (three to five meters relative to each other for a
thirty-five meter vessel). The hydrophone that is closest the
main propeller should be located on the port side of the
vessel.

• Hydrophones have a horizontal coverage of approximately

50 degrees. To maximise coverage using two hydrophones
they should be offset preferably 20 degrees outboard. With
this configuration the two hydrophones will overlap each
other by preferably 10 degrees and provide a total system
coverage of 90 degrees.

• Hydrophones have a vertical coverage of approximately 30

degrees. The normal tilt angle is 20 degrees; if the system is
to be used in deep water the hydrophones should be tilted
preferably 30 degrees and in shallow water preferably 10
degrees. To maximise coverage using two hydrophones when

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Simrad PI44

trawling in both deep and shallow water tilt one preferably
15 degrees and the other preferably 30 degrees. The
hydrophone closes to the propeller should be tilted the most
and care should be taken with regard to underwater acoustical
noise.

• Hydrophone cables pass through a vessel’s hull below its

water-line. It is therefore strongly recommended that a length
of conduit be fitted (using approve fastening procedures) to
the interior of hull around the opening made for the
hydrophone’s cable. This conduit should extend vertically
(inside the vessel) over the water-line so that hydrophone
cables can be safely passed through the hull without the
danger of flooding in the event of gland failure. Hydrophones
with steel through-hull fittings installed in this manner can be
replaced without the necessity of dry docking.

• The cable between the hydrophone and the cabinet must be

properly shielded from other potential sources of electrical
interference. A good practice is to run the hydrophone cable
in a steel conduit to the wheel house.

90

Figure 3 Recommended hydrophone locations

The illustration shows the recommended (A) and the alternative
(B) locations for single hydrophone locations. For a dual
installation, use position (A), and place the port hydrophone
further aft than the starboard. (L) is the total length of the hull
measured at the waterline.

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Coverage area, orientation and tilt

Once the fore-and-aft placement of the hydrophone is decided, it
is equally important to carefully consider its horizontal and
vertical orientation. Hydrophone orientation can have a large
influence on system performance.

Hydrophones must be configured so that they overlap one an
other in the horizontal plane. Tilt is decided by the actual depth
of the gear. If fishing operations are to be conducted in both
deep and shallow water the hydrophones can be tilted
differently.

Horizontal cove rage area

The hydrophone’s beam sensitivity is concentrated within a 50
degrees horizontal and -30 degrees vertical sector. By off-setting
hyprophones by 20 degrees each from the vessel’s centre line an
overlapping coverage area of 20 degrees is provided with a total
coverage area of 90 degrees.

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Horizontal coverage area
(A) = Starboard hydrophone
(B) = Port hydrophone

This “rule-of-thumb” is for normal trawling operations. For
pair-trawling or when fishing with Danish seines, the horizontal
position of the hydrophones should be configured with regard to
the operation in question.

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Simrad PI44

Vertical coverage area I

Dual hydrophone installation with hydrophones equally distant
from the bow, but tilted differently.

Typical tilt configuration for operation in both deep and shallow
water when the hydrophones have the same distance from bow.
The hydrophones may be installed in shoes or blisters.

(A) = Using shoes (top view)
(B) = Using blisters (top view)
(C) = Port hydrophone tilted 10 to 20 degrees
(D) = Starboard hydrophone tilted 20 to 35 degrees
(K) = Keel

The hydrophone on the starboard side of the hull should have
the greater tilt of the two, approximately 20 to 35 degrees. The
hydrophone on the port side of the hull should be tilted
approximately 10 to 20 degrees

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