Simrad 38-9 DATASHEET

Installation manual

Simrad 38-9

38 kHz Single beam transducer

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

www.SIMRAD.com

Simrad 38-9

Installation manual

This document provides a general description of how to install the Simrad 38-9 Single beam transducer. The information must be regarded as general guidelines and recommendations only. The installation shipyard must design and manufacture installation hardware to ﬁt the 38-9 transducer on each individual vessel.

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August 2006

Document history

Document number: 305265 / ISBN-10: 82-8066-074-7 / ISBN-13: 978-82-8066-074-9 Rev.A August 2006

Original issue.

Disclaimer

The information contained in this document remains the sole property of Simrad Horten AS. No part of this document may be copied or reproducedin any form or by any means, and the information contained within it is not to be communicated to a third party, without the prior written consent of Simrad Horte

nAS. Simrad H orten AS endeavours to ensure that all information in this d ocument is correct and fairly stated, but does not accept liability for any errors or omissions.

Warning

The equipment to which this manual applies must only be used for the purpose for which it was designed. Improper use or maintenance may cause damage to the equipm ent and/or injury to personnel. The user must be familiar with the contents of the appropriate manuals before a

ttempting to operate or work on the equipment. Simrad disclaims any responsibility for dam age or injury caused by improper installation, use or maintenance of t he equipment.

Support

If you require maintenance on your Simrad equipment, contact your local d ealer. You can also contact Simrad using the following e-mail address: e-mail: contact@simrad.com

Simrad Horten AS

Strandpromenaden 50 P. O. Bo x 1 11 N-3191 Horten, Norway

Telephone:+4733034000 Telefax:+4733042987

www.simrad.com

simrad.sales@simrad.com

Installation manual

Table of contents

INTRODUCTION ............................................. ................... 5

TRANSDUCER LOCATION .................................................. 6

Go deep.....................................................................................................................6

Vessel heave .............................................................................................................6

Noise from protruding objects on the hull................................................................6

Boundary water layer ...............................................................................................7

Propeller noise..........................................................................................................7

Inclination of the transducer face .............................................................................8

Summary and general recommendation...................................................................8

WAYS OF MOUNTING T HE TRANSDU CER......................... 10

Transducer blister ...................................................................................................11

Box keel..................................................................................................................17

Flush mounting in a steel tank................................................................................19

Acoustic window.................................................................................................... 21

Inside the hull .........................................................................................................23

Drop keel ................................................................................................................25

Retractable transducer ............................................................................................26

CABLE GLANDS ............................................................... 27

Order numbers........................................................................................................27

Cable gland for steel hulls......................................................................................28

Cable gland for wood or GRP hulls .......................................................................29

Cable glands for small hulls ...................................................................................30

Cable splicing.........................................................................................................31

STEEL CONDUIT.............................................................. 32

HANDLING AND M AINT ENANCE ...................................... 33

Approved anti-fouling paints..................................................................................34

DRAWING FILE ............................................................... 35

Single frequency, single beam, low pow er transducer connection.........................36

Outline dimensions.................................................................................................37

Mounting arrangement ...........................................................................................38

Mounting ring.........................................................................................................40

Blister assembly .....................................................................................................42

Blister design..........................................................................................................44

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INTRODUCTION

The purpose of this manual is the provide the basic information required to install the 38-9 Single beam transducer.

Note that although drawings are provided to explain the installation principles, the installation shipyard must provide the ﬁnal drawings required to ﬁt each individual vessel. Also, w hen applicable, the installation shipyard must have the drawings and installation approved by the proper authorities.

Transducer order number: KSV-203635. A cable gland kit for steel hull is included with the delivery.

Other cable glands must be ordered separately.

Transducer installation

The next chapter in this manual provides general guidelines for transducer installation. The drawings speciﬁc for the 38-9 transducer are located in the Drawing ﬁle.

Introduction

Technical speciﬁcations

Refer to the 38-9 Product speciﬁcation.

Additional parts

The following items can be supplied by Simrad to facilitate installation:

• Mounting ring: Order number 499–203336

• Transducer cable (for extension): Order number 642–016604

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Simrad 38-9

TRANSDUCER LOCATION

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 s urface. 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.

WARNING 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.

Noise 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 ﬂow 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 t ransducer 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.

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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.

Transducer location

(CD17004P)

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.

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

BAC

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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 k eel where the propeller blades move upwards, because the propeller cavitation is strongest on the other side. The cavitation starts m ost 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 t he 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.

Inclination of the transducer face

Ideally, the transducer face should be mounted in parallel with the sea surface when the vessel is in normal trim, as this will provide the most accurate echo information. However, it is also very important that the w

In order to ensure laminar ﬂow, the transducer face may be tilted slightly upwards in relation to the water ﬂow. This allows the ﬂowing water to meet the face directly, and assures laminar ﬂow. The inclination angle must however be determined carefully. The angle must be small on transducers with narrow beam angles. As a rule of thumb, mount transducers with beam angles smaller than seven degrees with minimum inclination angle. The smaller beam angle your transducer has, the smaller the inclination angle can be.

Ensure that you do not mount the transducer with a negative inclination angle. This may cause turbulence under the transducer face, and reduced echo sounder performance.

ater ﬂow over the transducer face is laminar.

Summary and general recommendation

Some of the above guide lines are conﬂicting, and each c ase 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.

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Transducer location

(CD017004Q)

General recommendation for transducer location: (A) = Transducer (B) = Inclination angle (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.

(CD17004C)

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

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WAYS OF MOUNTING THE TRANSDUCER

There are many different ways to mount the transducer. These are the recommended methods to mount a circular transducer.

Topics

Transducer blister on page 11 Box keel on page 17 Flush mounting in a steel tank on page 19 Acoustic window on page 21 Inside the hull on page 23 Drop keel on page 25 Retractable transducer on page 26

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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 size 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 r ing will then secure the transducer between them. Note that several transducers use direction guides to allow correct mounting.

Ways of mounting the transducer

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.

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Simrad 38-9

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 t ransducer. The purpose of this support is to prevent the transducer from being pushed up into the blister in heavy seas.

(CD017010A)

(A) = Streamlined blister (B) = Stiffening rib (C) = Drainage holes (D) = Inclination angle

(G) = Cable service loop (H) = Stufﬁng tube (I) = Minimum 400 mm (J) = Rounded c orners

(E) = U-shaped support bar (F) = Forward

(K) = Air outlet

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Ways of mounting the transducer

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.

(CD017010B)

(A) = Streamlined blister (B) = Mounting ring (C) = Clamping ring

(E) = Air outlet (F) = Forward (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.

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Example: Medium sized transducer without clamping ring

The illustration below shows a transducer blister designed for a medium sized transducers. The same blister design principles apply. Note that the transducer is mounted without a clamping ring, which makes it necessary to use a different mounting ring design.

(CD017010E)

(A) = Streamlined blister (B) = Mounting ring (C) = Bolt (D) = Self-locking threads

(E) = Air outlet (F) = Forward (G) = Transducer cable (H) = Transducer

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.

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