KROHNE BM70M User Manual

Installation and
operating instructions for

BM 70 M

Inclusive Part 2
Supplementary Installation and
operating instructions for
BM 70 M-EEx / BM 70 Mi-EEx

©

KROHNE 08/2002 7.10027.21.00

GR

Variable area flowmeters
Vortex flowmeters
Flow controllers
Electromagnetic flowmeters
Ultrasonic flowmeters
Mass flowmeters

Level measuring instruments

Communications engineering
Engineering systems & solutions
Switches, counters, displays and recorders
Heat metering
Pressure and temperature

Part 1: Installation and operating instructions for BM 70 M

1 Range of applications.....................................................................................................................................................5

2 Mode of operation and system structure......................................................................................................................5

2.1 Operating principle (FMCW-Radar) ..................................................................................................................................5

2.2 Signal processing (digital).................................................................................................................................................6

2.3 Modularity (signal converter, flange, antenna)..................................................................................................................7

3 Input .................................................................................................................................................................................7

3.1 Measured variable (distance, level, volume, reflection)....................................................................................................7

3.2 Measuring range...............................................................................................................................................................7

3.3 Block distance...................................................................................................................................................................8

3.4 Out-of-range performance.................................................................................................................................................8

4 Output ..............................................................................................................................................................................8

4.1 Variants.............................................................................................................................................................................8

4.2 Ex-e current output HART

4.3 Ex-i current output HART

4.4 HART

®

communication ...................................................................................................................................................10

4.5 Current output (non-communicable) ...............................................................................................................................11

4.6 Digital interface RS 485 ..................................................................................................................................................11

4.7 Breakdown signal............................................................................................................................................................12

4.8 Digital input .....................................................................................................................................................................13

5 Measuring accuracy......................................................................................................................................................13

5.1 Reference conditions ......................................................................................................................................................13

5.2 Error of measurement.....................................................................................................................................................13

5.3 Repeatability ...................................................................................................................................................................14

5.4 Measured value resolution/hysteresis.............................................................................................................................14

5.5 Transient recovery time...................................................................................................................................................14

5.6 Long-term drift.................................................................................................................................................................14

5.7 Effect of ambient temperature.........................................................................................................................................14

6 Operating conditions....................................................................................................................................................14

6.1 Installation conditions......................................................................................................................................................15

6.1.1 Transmission angle.........................................................................................................................................................15

6.1.2 Recommendations for positioning on the tank................................................................................................................15

6.1.3 Mounting on tank fitting...................................................................................................................................................17

6.1.4 Mounting on stilling wells/ trunks.....................................................................................................................................18

6.1.5 Wave-Guide....................................................................................................................................................................19

6.1.6 Curved antenna extensions ............................................................................................................................................20

6.1.7 Special options for the flange..........................................................................................................................................20

6.1.8 Ultimate installation on the tank......................................................................................................................................21

6.2 Ambient conditions..........................................................................................................................................................21

6.2.1 Hazardous locations........................................................................................................................................................21

6.2.2 Ambient temperature of signal converter........................................................................................................................21

6.2.3 Flange temperature.........................................................................................................................................................21

6.2.4 Ambient temperature limits .............................................................................................................................................22

6.2.5 Storage temperature.......................................................................................................................................................22

6.2.6 Environment class...........................................................................................................................................................22

6.2.7 Protection category.........................................................................................................................................................22

6.2.8 Shock resistance.............................................................................................................................................................22

6.2.9 Vibration endurance limit.................................................................................................................................................22

6.2.10 EMC................................................................................................................................................................................22

6.3 Product conditions...........................................................................................................................................................22

6.3.1 Physical properties of the products.................................................................................................................................22

6.3.2 Relative permittivity (

6.3.3 Product limitations...........................................................................................................................................................23

6.3.4 Product temperature (unrestricted).................................................................................................................................23

6.3.5 Maximum allowable operating pressure..........................................................................................................................23

6.4 Maintenance....................................................................................................................................................................24

®

...............................................................................................................................................9

®

(type of protection: Ex de [ia]) ..............................................................................................10

1.5)..........................................................................................................................................23

ε

≥

r

2 BM 70 M

7 Design............................................................................................................................................................................24

7.1 Dimensions and weights.................................................................................................................................................24

7.2 Replacement of the signal converter .............................................................................................................................. 25

7.3 Field assembly................................................................................................................................................................26

7.4 Materials of construction.................................................................................................................................................26

7.4.1 Signal converter..............................................................................................................................................................26

7.4.2 Flange system.................................................................................................................................................................27

7.4.3 Seals and gaskets...........................................................................................................................................................27

7.5 Process connection.........................................................................................................................................................27

7.6 Electrical connection.......................................................................................................................................................28

7.7 Terminating resistor for the RS 485 interface.................................................................................................................30

8 User interface................................................................................................................................................................30

8.1 Local display................................................................................................................................................................... 30

8.2 Function of the keys........................................................................................................................................................ 31

8.3 Operator control concept ................................................................................................................................................32

8.4 Table of settable functions (Versions 3.00, 3.01, 3.02, 3.03, 4.02, 4.03)........................................................................ 34

8.5 Configuration examples.................................................................................................................................................. 39

8.5.1 Level measurement (example) ....................................................................................................................................... 40

8.5.2 Volume measurement (example).................................................................................................................................... 40

8.6 Description of functions...................................................................................................................................................41

8.6.1 Choice of units................................................................................................................................................................ 41

8.6.2 Vessel (tank) height........................................................................................................................................................ 43

8.6.3 Block distance, antenna type and antenna extension.....................................................................................................44

8.6.4 Distance piece ................................................................................................................................................................44

8.6.5 Stilling well...................................................................................................................................................................... 45

8.6.6 Reference and tank bottom offsets.................................................................................................................................45

8.6.7 Display............................................................................................................................................................................ 47

8.6.8 Current output I...............................................................................................................................................................48

8.6.9 Communication interfaces .............................................................................................................................................. 49

8.6.10 Display ............................................................................................................................................................................50

8.6.11 Auto tank height.............................................................................................................................................................. 51

8.6.12 Empty spectrum.............................................................................................................................................................. 51

8.6.13 Time constant and tracking speed.................................................................................................................................. 54

8.6.14 Multiple reflections and block distance detection............................................................................................................54

8.6.15 Tank bottom tracing system............................................................................................................................................55

8.6.16 Tank type, movement of product surface........................................................................................................................ 56

8.6.17 Switching output.............................................................................................................................................................. 56

8.7 Functional checks........................................................................................................................................................... 59

8.7.1 Main menu 2.0 Test functions......................................................................................................................................... 59

8.7.2 Hardware test..................................................................................................................................................................59

8.7.3 Test of current output...................................................................................................................................................... 60

8.7.4 Test of switching output.................................................................................................................................................. 61

8.7.5 Display of firmware version............................................................................................................................................. 61

8.8 Pointers and error messages during measurement........................................................................................................61

8.8.1 Different kinds of messages............................................................................................................................................61

8.8.2 Pointers provided by 6 markers during measurement....................................................................................................62

8.8.3 Error messages and their representation in display and at outputs................................................................................63

8.8.4 Error display during measurement.................................................................................................................................. 64

8.8.5 Error list...........................................................................................................................................................................64

8.9 Messages on start-up .....................................................................................................................................................64

8.10 Faults and symptoms during start-up and measurement................................................................................................ 64

8.11 Calculation of the measured value..................................................................................................................................70

8.12 User program PC-CAT for Windows............................................................................................................................... 70

9 Power supply.................................................................................................................................................................71

9.1 Options, technical data ...................................................................................................................................................71

9.2 Fuses.............................................................................................................................................................................. 72

9.3 Changeover of operating voltage and replacement of fuses .......................................................................................... 72

9.4 Advice on safety..............................................................................................................................................................73

10 Certificates and approvals........................................................................................................................................... 75

10.1 Declaration of Conformity ...............................................................................................................................................75

11 Ordering information....................................................................................................................................................76

12 External standards, codes and directives.................................................................................................................. 77

13 Quality assurance.........................................................................................................................................................77

BM 70 M 3

General advice on safety

Weight: the device will weigh between approx. 55 kg (120 lb) and 70 kg (155 lb)
or more!
To carry, use both hands to lift the device carefully by the converter housing. If
necessary, use lifting gear.
Avoid hard blows, jolts, knocks, impacts, etc.

Product liability and warranty

The BM 70 M level gauge is designed solely for measuring the distance, level, volume and
reflection of liquids, pastes, slurries, solids and particulate materials.
The BM 70 M level gauge does not form part of an overfill protection system as defined in WHG.
Special codes and regulations apply to its use in hazardous areas.
Responsibility as to suitability and intended use of these level gauges rests solely with the user.
Improper installation and operation of our level gauges may lead to loss of warranty.
In addition, the "General conditions of sale", forming the basis of the purchasing contract, are
applicable.
If you need to return the level gauge to the manufacturer or supplier, please refer to the
information given on page 86.

Items supplied

Depending on the version ordered we supply the following:

Signal converter bolted to waveguide window and antenna

•

Optional: antenna extension, sunshade (with fastening material in each case)
Report on factory settings for the signal converter

•

Bar magnet for operator control / parameter assignment (only in version with local display)

•

Wrench for the covers

•

Installation material (stud bolts, flange gasket and cabling) not supplied, to be provided by

•

customer!

Documentation supplied

Condensed instructions: installation, connection, start-up and safety advice in condensed form,
but sufficient for most applications. Please read through these instructions first!
Instruction card: overview of the configuration menu and meaning of the markers in cheque card
format.
Installation and operating instructions (this manual): detailed user manual and reference book,
including description of special versions and functions. This documentation is structured on lines
similar to those given in the DIN V 19259 Standard.
Approval documents, unless reproduced in the installation and operating instructions.

Software history

Introduction
Mth./Yr
06/02 4.04 06/02 First serial version
06/02 4.06 06/02 Minor amendments

4 BM 70 M

Firmware
version

Device
instructions

Remarks

1 Range of applications

The BM 70 M Level-Radar level gauging system is designed to measure the distance, level,
volume and reflection of liquids, pastes, slurries, solids and particulate materials.
BM 70 M Ex hazardous-duty versions are suitable for use in Ex-Zone 0, 1 and 2.

2 Mode of operation and system structure

2.1 Operating principle (FMCW-Radar)

A radar signal is given via an antenna, reflected on the measuring surface and received after a
delay time t.

FMCW: Frequency Modulated Continuous Wave

The FMCW-radar uses a high frequency signal (~10 GHz) which transmits frequency increasing
linearly 1 GHz during the measurement (frequency sweep) (1). The signal is emitted, reflected on
the measuring surface and received time-delayed (2).
For further signal processing the difference ∆f is calculated from the actual transmit frequency
and the receive frequency (3). The difference is directly proportional to the distance i.e. a large
frequency difference corresponds to a large distance and vice versa.
The frequency difference is transformed via a Fourier transformation (FFT) into a frequency
spectrum and then the distance is calculated from the spectrum. The level results from the
difference between tank height and distance.

Linearity of frequency sweeps

The measuring accuracy of an FMCW radar is determined from the linearity of the frequency
sweeps and their reproducibility. The linearity correction is deduced via reference measurement
of the oscillator.
An immediate frequency regulation is necessary with the BM 70 M device because of the higher
demand on the measuring accuracy.
With the PLL technology (Phase Locked Loop) the signal frequency is directly recorded as a
digital data and the converter oscillator locks automatically on the right frequency.

3) differential frequency
formed

f

∆

f

1) radar frequency
linearly changed

antenna

2) delay time due to wave
propagation

t

non-linear sweep linear sweep

∆

f

f

Start

BM 70 M 5

f

Stop

As the transmit frequency is changed during a short time interval by FMCW radar the transmitted

g

g

g

g

e

frequency has to follow the nominal frequency within micro seconds. This ensues via modern, fast
electronic and processors.

PLL structure

Microprocessor

control

Microwave
oscillator

Loop
filter

Antenna

Reference
oscillator

Phase
detector

2.2 Signal processing (digital)

The radar signals are digitally processed by a microprocessor. The processing system is based
on intelligent procedures that allow for plausibilities and history.

The following diagram describes the path of internal signal processing:

measurement
si

nal

ain

switch

V

ain

control

filter

analog to

ital

di

conversion

Fourier

transform

850.97:2

empty tank spectrum

plausi-

bility

spectrum

interpolation

corrected

spectrum

distanc

After automatic gain control, the measuring signal is filtered, digitized and converted into a
frequency spectrum by means of the Fourier transform. Plausibility of the value obtained is
assessed with the aid of the so-called empty-tank spectrum, which contains information about
constant interference reflectors. Interpolation of the spectrum helps to improve resolution of the
measured value.

OO

OO

6 BM 70 M

2.3 Modularity (signal converter, flange, antenna)

The measuring system consists of the flange system and the signal converter.
The flange system contains the microwave window separating product from pressure, and the
antenna system.
The compact signal converter contains the microwave generator and the entire signal processing
system, including provision of a standardised output signal (4 - 20 mA or digital interface).
The signal converter can be separated from the flange system under process conditions, without
loss of pressure or escape of product.

V96 version SA version

Converter

Flange

Antenna system

3 Input

3.1 Measured variable (distance, level, volume, reflection)

The primary measured variable is the distance between a reference point (as standard: tank
mounting flange) and a reflecting surface (e.g. surface of the liquid).
The filling level is determined by allowing arithmetically for the entered tank height.
Volume measurements are possible by entering a conversion table (max. 50 points).
The strength of the reflected signal can be measured for qualitative assessment of the tank
product or its surface.

3.2 Measuring range

Maximum tank height 0.5 m (20 inch)
Maximum measuring range 35 m (115 ft)

[0.5 - 35/40 m (1.64 - 115/131 ft)]
The useful range will depend on the antenna size, the reflection properties of the tank product,
the installation position, and the presence of interference reflectors (see Sections 6.1).

BM 70 M 7

3.3 Block distance

The block distance is the minimum measured distance between the mounting flange (reference
point) and surface of the tank product.

Recommended minimum values:

Block

distance

Maximum

level

Horn antenna without stilling well Stilling well / Wave-Guide

Antenna size * = Type1: 11cm/4";

Antenna size* = Type3: 22cm/8.7"; Type4: 34cm/13";

* Hastelloy: +3cm / 1,2 "

Recommended antenna distance:
Storage tanks: 10cm/4"; Process tanks: 20cm/8"

Product surface

The length of any antenna extension used must be
added on!

Type2: 15cm/5.5"; Type3: 22cm/8.7"
Wave-Stick SW: 6cm/2.4"

(Wave-Guide: no antenna)

Recommended antenna distance =
30 cm / 12"

Product

* Hastelloy: 3 cm (0.4")

3.4 Out-of-range performance

When the level measuring range is exceeded (including flooding) the measured value will stick at
the (adjustable) block distance (see Sect. 8.6.14).
If the measured value drops below the level range, it will stay put at the set lower range limit
(distance = tank height).

4 Output

4.1 Variants

Variants Remarks Described

in Section

Ex-e current output

®

HART
Ex-i current output HART® intrinsically safe; passive; HART® protocol

Current output Ex-e; active; non-communicable 4.5
RS 485 + current output BM70 protocol or ModBus-RTU or HART® 4.6 + 4.5
PROFIBUS-PA intrinsically safe; see Supplementary Instructions ­Foundation Fieldbus (FF) intrinsically safe; see Supplementary Instructions -

All versions with HART® or BM70 protocols can be operated with the PC-CAT PC program (see
Section 8.12).

8 BM 70 M

Ex-e; active; HART® protocol;
together with switching output and digital input

(optionally with intrinsically safe switching output)

4.2 + 4.4

4.3 + 4.4

Overview of digital Communication possibilities:

BM 70 A

RS 485

4 ... 20mA
+ HART ®

Converter

HART
FIELD COMMUNICATIONS

F1 F2 F3 F4

HART Communicator

I

>>>

O

A B C D E F G H

7 8 9

J K L M N O P Q

4 5 6

S T U V W X Y Z

1 2 3

# % & < > : +

*

0 . _

HART-

HHC

PC-CAT

or

HART specific software

and operating devices

4mA (Ex i)
+ HART®

HART
FIELD COMMUNICATIONS

F1 F2 F3 F4

HART Communicator

I

>>>

O

A B C D E F G H

7 8 9

J K L M N O P Q

4 5 6

S T U V W X Y Z

1 2 3

# % & < > : +

*

0 . _

HART-

HHC

HART-Master

Point-to-point Multidrop

RS 485

communication interfaces

Modbus
PROFIBUS-PA

...........

Other

Tank Inventory System

4.2 Ex-e current output HART

®

Function Level, distance, volume (conversion table) or reflection, and error

identification; galvanically isolated from digital input and switching

output
Current 4-20 mA; without or with error message (2 mA and 22 mA)
Accuracy/linearity 0.05 % (rel. 20 mA; at T = 20°C, 100ohm load impedance and nominal

operating voltage)
Temperature drift < 100 ppm/K (typically 30 ppm/K)
Load impedance < 500 ohm
Effect of load

< 0.02 % (rel. 20 mA for RB = 0...500 ohm)
impedance
Effect of power 0.02 % (rel. 20 mA for UB within limits of tolerance)
Hazardous-duty

Ex e
version
Note together with switching output and digital input

Digital input (terminals 81/82):

Can be used to suspend the entire measurement procedure, i.e. measurements are "frozen"
(standard setting), or to hot start the device (reprogramming by KROHNE Service).

Applicable voltage 5...28 V DC
Input resistance > 1 kohm

Switching output (terminals 41/42):

Can be programmed as a limit switch, alarm contact or error message. The contact is open in the
de-energized condition.

Operating data max. 100 mA / 30 V DC or 30 V AC
Internal resistance < 20 ohm

BM 70 M 9

4.3 Ex-i current output HART® (type of protection: Ex de [ia])

Function Level, distance, volume (conversion table) or reflection; and error

identification; passive output (current sink)

Current 4-20 mA; without or with error message (3.6 mA / 22 mA);

4 mA constant, adjustable for HART®-Multidrop
Temperature drift < 100 ppm/K (typically 30 ppm/K)
Accuracy/linearity 0.05 % (rel. 20 mA; at T = 20°C, 10 V supply voltage and nominal

operating voltage)
Supply voltage U 8-30 V (between terminals 31 and 32)
Load impedance < (US - 8V) / 22 mA. (US = external supply voltage)
Effect of supply voltage < 0.02 % (rel. 20 mA for U = 8...30 V)
Effect of power < 0.02 % (rel. 20 mA for UB within limits of tolerance)
Note Digital input not available

Optional switching output (terminals 41/42):

Can be programmed as limit switch, alarm contact or error message. The contact is open in the
deenergized condition.

Operating data 6...30 V; I

< 110 mA; U

Low

Low

< 2V; I

< 900 µA (U=30V) and I

High

High

= 200 µA (U=8V)

Ex-i safety limits

Signal circuit in type of protection: Intrinsic Safety EEx ia IIC/IIB or EEx ib IIC/IIB for connection to
a certified intrinsically safe circuit with the following peak values:
U

= 30 V; Ik = 250 mA

o

Effective inner capacitance ≈ 0; effective inner inductance ≈ 0

4.4 HART® communication

The HART® Communications protocol can, in accordance with the Rosemount Standard, be used
with a BM 70 M.
Electrical connection: see Section 7.6.

There are two ways of using the HART® Communication:

Point-to-point connection Multipoint connection (Multidrop)

between the BM 70 M and the HART
master equipment.
A BM 70 M can be used either with an
Ex-e current output HART® or with an
Ex-i current output HART®.

HART
Master

4...20 mA

®

with up to 15 devices (BM 70 M or other HART
equipment), in parallel on a 2-wire bus. A BM 70 M is
normally used with Ex-i current output, but an Ex-e
current output can also be used (constant 4 mA in
both cases).

HART
Master

4mA 4mA 4mA 4mA

other

HART
device

®

other
HART

device

10 BM 70 M

)

4.5 Current output (non-communicable)

Function Level, distance, volume (conversion table) or reflection, and error

identification
Current 4-20 mA; without or with error message (2 mA and 22 mA)
Accuracy/linearity 0.3 % (rel. 20 mA; at T = 20°C, 100 Ohm load impedance and

nominal operating voltage)
Temperature drift < 200 ppm/K (typically 70 ppm/K)
Load impedance < 250 Ohm
Effect of load impedance < 0.1 % (rel. 20 mA for RB = 0...250 Ohm)
Effect of power < 0.1 % (rel. 20 mA for UB within limits of tolerance)
Hazardous-duty version Ex e

When operated as a switching output (digital output):

Function limit switch, alarm contact or error message
Low status current < 2 mA
High status current = 22 mA (when load < 250 Ohm)
No-load voltage < 18 V

4.6 Digital interface RS 485

RS 485 is a bus that allows two-way Communication (half-duplex operation) with the BM 70 M
Level-Radar. When the computer system sends out a request, the BM 70 M transmits: level,
distance; volume (conversion table), reflection, setting parameters and status.
A PC can configure any BM 70 M via the bus (RS 485/RS232 converter required) by means of
the PC-CAT program, provided no master is active. The maximum cable length - excluding
amplifier - is 2000 m.

Transmission rate 1200 to 38400 bauds
Address 0 to 255
Protocols KROHNE Protocol, HART®, Modbus RTU (from firmware

V.3.02/4.02)

Additional information: see "BM 70 A/P Communication RS 485"

instructions.
Additional current output The current output is conductively coupled to the RS 485 interface.

Technical data: see Section 4.5
Note Switching contact and digital input are not available.

However, the current output can be configured as a switching

output.

Various bus configurations

A) Connection of a BM 70 M as a single RS 485 user:

Computer
system

RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B

Bus line (2 shielded wires)

with termination

resistance

120 ohms

BM 70 M 11

B) Connection of several BM 70 M in the RS 485 bus system via stubs to the bus cable:

Computer
system

RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B)

Bus line (2 shielded wires)

without
termination
resistance

termination
resistance

without

...........

without
termination
resistance

with termination

resistance

120 ohms

C) Connection of several BM 70 M in the RS 485 bus system, with bus cable looped through to
further field instruments:

Computer
system

RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B)

without
termination
resistance

Bus line (2 shielded wires)

...........

without
termination
resistance

without
termination
resistance

with termination

resistance

120 ohms

If other devices are operated together with the BM 70 M Level-Radar on one

•

bus, all devices must use the same Communications protocol (e.g. ModBus
devices of different makes or BM 70 M and MTM 70 with KROHNE
Protocol).
When "HART

•

with the "HART

®

" is set as the protocol type, use only the protocol in keeping

®

Specification". The "Hardware Implementation RS 485"
does not conform to the HART® Standard (see Sections 4.2 and 4.3).
Since signal reflections at the line ends can interfere with Communication,

•

both the line beginning (at the computer system) and the line end (at the last
device) should be terminated with the typical surge impedance of the cable
(120 Ohm). To do this inside the BM 70 M: see Section 7.7.

4.7 Breakdown signal

Breakdown information can be called up via the following interfaces:

Local display: flashing display, plain text information

•

Current output: error signal 2 mA (Exi = 3.6 mA) or 22 mA

•

Switching output: contact opens or closes

•

Digital interfaces: interrogation of error flags

•

12 BM 70 M

4.8 Digital input

The digital input (for electrical data: see Section 4.2) can be used for temporarily "freezing"
measurements or for carrying out a hot start. It is only available in the "Ex-e current output
HART®" version.
The "freeze" function can be used to blank out larger, temporary interferences, e.g. very slow
agitator, slide gate, ball valve in the stilling well. The last measured values in each case are
present at outputs I and S, and in the display. The digital input is also taken into account when
the empty-tank spectrum is being recorded (totalizer does not continue). Marker 6 in the display
indicates that the digital input is active in the "freeze" function.

The function of the digital input is set as standard to "freeze". To switch the
function to "hot start" or to deactivate it completely, the setting will need to be
changed in the Service menu of the BM 70 M.

5 Measuring accuracy

5.1 Reference conditions

Temperature +20°C / +68°F
Pressure 1013 mbar abs. / 14.5 psia
Air humidity 65%
Highly reflecting product (e.g. water) with calm surface
Tank diameter > 5 m / 16.4 ft
Mounted at least 1/7 x tank height away from tank edge (BM 70 M: 1/5 x tank height)
No interference reflections inside the radiation lobe (± 6...9°; see Section 6.1.1)

5.2 Error of measurement

Since the measuring process primarily determines distance, measuring accuracy can only be
specified as a function of the distance. For that reason, all figures given in this Section 5 refer to
the measured distance.

Only with antenna type 4 (200 mm / 7.87") or stilling well 100 - 200 mm dia. (4 - 8")

Accuracy

inch mm

0.48

12
10

0.4

0.32

0.24

0.16

0.08

-0.08

-0.16

-0.24

-0.32

-0.4

-0.48

±

8

20

...

6

30

mm

4
2

0

0

-2

-4

-6

-8

-10

-12

± 2 mm (0.04")

0 5 10 15 20 25 30 35 40 m

Block-

distance

1

16 33 49 66 82 98 1153

Distance to flange

± 0.01 %

BM 70 M 13

131ft

5.3 Repeatability

Repeatability is equal to half the value for the error of measurement.

5.4 Measured value resolution/hysteresis

Measured value resolution is 0.1 mm / 0.004" for BM 70 M.
Hysteresis is at least 20 times less than the error of measurement.

5.5 Transient recovery time

The transient recovery time is determined by the setting parameter "time constant" (1 ... 100 s).
The transient recovery time relative to 1% deviation from the steady-state value is approx. 4.6
times the time constant.
However, in the case of unusually rapid changes in level, the transient recovery time may deviate
from this figure.

5.6 Long-term drift

The long-term drift is within the specified error of measurement.

5.7 Effect of ambient temperature

Temperature coefficient, signal output:
Ex-e current output HART
Ex-i current output HART® < 100 ppm/°C (typically: 30 ppm/°C)
Current output < 200 ppm/°C (typically: 70 ppm/°C)
Digital interfaces no temperature effect
The temperature has no effect on the measured value as the device carries out a regular self­calibration.
The temperature of the atmosphere above the liquid product results theoretically in -1 ppm/°C for
air.
When ascertaining temperature effects using reference measurements in liquid tanks, it needs to
be remembered that liquids generally have a high coefficient of expansion (organic liquids:
typically 0.15 %/°C)!

®

< 100 ppm/°C (typically: 30 ppm/°C)

6 Operating conditions

Hazardous-duty systems:

The BM 70 M is certified in conformity with European Standard (ATEX) for use in Zone 0, 1

•

and 2 hazardous locations.
The BM 70 M also has FM Approval (Factory Mutual) for CLASS I, DIV 1, GROUPS B,C,D;

•

CLASS II/III, DIV 1, GROUPS E,F,G (in preparation)
Attention is drawn to the information given on the nameplate and the specifications in the

•

approval certificates.
When carrying out installation, dismantling work or making electrical connections in the

•

hazardous area, be sure to observe the pertinent wiring and installation regulations, e.g. as
specified in VDE 0165.
Within the scope of routine checks required to be carried out on systems operated in

•

hazardous areas (maintaining the system in good working order), the "flameproof enclosure"
(large cover on signal converter) should also be visually inspected for signs of external
damage and corrosion.
Before opening the "flameproof enclosure" (e.g. to inspect the inside or for repair purposes)

•

make absolutely certain in the hazardous location:

- that the BM 70 M Level-Radar is disconnected from voltage, and then allow the prescribed
waiting time of 22 minutes to elapse first,

- and that there is no explosion hazard (gas-free certificate!).

14 BM 70 M

yp

Safety:

Operator control via the keys: on electrical safety grounds, operator control of the keys (below

•

the display, with the housing open) may only be carried out by specialist personnel for service
and repair work, on no account, however, when there is risk of explosion!
Surface temperature: the housing of the signal converter can, in extreme ambient conditions,

•

assume temperatures of more than 70°C (158°F)!

6.1 Installation conditions

6.1.1 Transmission angle

The transmission angle is defined as the angle
radar waves assumes half the value of the maximum power density (half-power beam width):

. to the vertical, in which the power density of the

Antenna
Type

Diameter
mm
(inches)

Type 4 200 (7.87) 6° 10 cm (3.94”)
Type 3s* 140 (5.51) 8° 14 cm (5.51”)
Type 2s* 100 (3.94) 12° * 22 cm (8.67”)
Type 1s* 80 (3.15) 16° * 30 cm (11.8”)
Wave-Guide
/ stilling well

25-200
(0.98-7.87)

* Should only be used in stilling wells; the transmission angle given

αα

s

applies to line-of-sight propagation, i.e. without stilling well.

6.1.2 Recommendations for positioning on the tank

A) Horn antenna or Wave-Stick without stilling well

Recommended distance from
the tank wall

Lower measuring range
limited when tank has tapered
bottom.

Antenna T
or Wave-Stick

e 3

Transmissi
on angle α

Lobe expansion s
per metre distance

Propagation only inside the stilling
well

Several BM 70 M can be
operated in one tank.

>1/7×H, but max. 1/3×D

D

H

min.
measurable
level

BM 70 M 15

Do not position in tank
centreline! (multiple
reflections!)

Do not mount dead centre on
manhole cover! (multiple
reflections!)

Do not position above
internals! (interference
reflections!)

If these recommendations cannot be followed because of the tank geometry, please consult
KROHNE.

B) Stilling well or Wave-Guide

A stilling well or Wave-Guide may be mounted in any position on the tank.
(For design layout: see also Section 6.1.4; for block distance: see Section 3.3).

Stilling well application

16 BM 70 M

6.1.3 Mounting on tank fitting

A) Horn antenna

Should be mounted on the tank fitting as close to the horizontal as possible (deviation < ± 2°).
Exception: if product surface is not horizontal, (e.g. particulate materials) the flange can be
aligned roughly parallel to it.

The antenna should project out of the fitting:

Antenna Diameter D Length l*

Type 4 200 mm (8”) 335 mm (13.2”)
Type 3 140 mm (5.5”) 223 mm (8.8”)

Tank nozzle

L

* Hastelloy: + 30 mm (1.2”)

D

(subject to change without notice)

An antenna extension should be added if the antenna does not project out of the fitting:

Antenna

Tank nozzle

extension

Antenna extensions are available from 100 to 2000 mm (3.94" to 78.74") in steps of 100 mm
(3.94"). Several extensions can be joined up.

Exception:

When the tank fitting is symmetrical, the antenna may end in the fitting so as to enlarge the
measuring range (minimum dead zone to tank cover, see Sect. 3.3 "block distance" and Sect. 5.2
"error of measurement"):

Tank nozzle

BM 70 M 17

B) Solid antenna

6.1.4 Mounting on stilling wells/ trunks

Antenna Type Outside diameter
1s 76 mm (2.99”)
2s 100 mm (3.94”)
3 140 mm (5.51”)
3s 152 mm (5.98”)
4s 200 mm (7.87”)

If necessary, turn antenna to size!

Further requirements on stilling wells:

The well must be electrically conductive.

•

Minimum inside diameter of well: 40 mm (1.57"). (BM 70 M: 80 mm, better > 100 mm).

•

If possible, use only smooth walled, straight stilling wells. If nevertheless an assembled stilling

•

well is necessary, abrupt changes in diameter along the pipe should be less than 1 mm
(0.04"). Surface roughness of the inside of the pipe should not be more than + 0.1 mm
(0.004").
For the BM 70 M the antenna types 1s, 2s, 3s or 4s have to be used to achieve a high

•

measuring accuracy.

It is possible to measure through a full-bore open ball valve if the valve and the pipe adapters
above and below the valve are relatively smooth-walled.

It is not possible to measure levels below the end of the stilling well.
To ensure equalization of pressure, drill one or two small holes in the stilling well above the

maximum filling level.

18 BM 70 M

If necessary, several holes can be drilled along the whole length of the pipe. All holes must be

/

deburred. The holes should be as small as possible and spaced wide apart (Recommendation:
see drawing below).

Ø max.

10 mm

0.4’’

min.

50 mm / 1.97’’

It is advisable to fit a reference point at the end of the stilling well in the form of a rod or screw of
approx. 6 mm (0.24") diameter. See drawing below.

6 mm Ø
Ø 0.24’’

6.1.5 Wave-Guide

The "Wave-Guide" is a pipe with an outside diameter of 30 mm (1.18") and an inside diameter of
25 mm (0.98"), that is bolted direct to the BM 70 flange system (in the same way as an antenna
extension). It functions like a stilling well and can be used for clean products. The Wave-Guide is
not practical in conjunction with the BM 70 M as it will not provide high measuring accuracy.

Maximum length:
Ex: max. 3 m (9.84 ft) (except tantalum: max. 1 m (3.28 ft)).
Non-Ex: up to 3 m (9.84 ft) without additional support

Pipes longer than 3 m (9.84 ft) need to be fixed at two points.

BM 70 M 19

6.1.6 Curved antenna extensions

Rectangular and S-shaped extensions are available for particularly difficult operating conditions.
Such extensions can be used in cases where the antenna is exposed to especially high
temperatures and where there are problems of space, (e.g. to avoid internals; positioning the
antenna away from the centre of symmetry; lateral mounting of the signal converter).

Standard sizes (others on request):

271 (10.67")

271 (10.67")

Dimensions in mm (inches)

6.1.7 Special options for the flange

Antenna heating/cooling device
(> DN150/6")

Double-walled antenna for cooling or heating,
e.g. to avoid condensation (recommended for
liquid sulphur).
max. differential pressure at antenna:
Standard DN150 = 6 bar (87 psig)
(information on other pressure levels
provided on request)

271 (10.67")

R 110 (4.33")

300 (11.81")

323 (12.72")

Purging device
(> DN100)

With connection for purging the inside surface of
the antenna to prevent heavy deposits of product
or to heat or cool the antenna

20 BM 70 M

Antenna heating/cooling device
(> DN150/6")

Hazardous-duty systems:
In Zone 0, the temperature of the heating
system and antenna may not exceed 80 % of
the ignition temperature of the stored
material.
Continuous monitoring shall ensure, and
operational inspections shall verify, that the
80% level of the ignition temperature stated
in Point 1 above is not exceeded.

Purging device
(> DN100)

If a liquid is used for purging, this may interfere
with the functioning of the BM 70 M during the
process. Continuous purging with gas is not a
problem as it does not interfere with
measurements.
The purge connection is closed off by the
manufacturers with a ¼" screw. When this screw
is removed to connect up a purging system, the
operator is responsible for ensuring conformity
with "Ex" requirements in connection with the
purging circuit (e.g. fitting a flame trap).

6.1.8 Ultimate installation on the tank

After carefully positioning the BM 70 M on the tank fitting flange (not forgetting the gasket), align
the BM 70 M and the gasket.

Insert stud bolts and tighten nuts slightly (by hand). (These items not included with supply).
Tighten down stud bolts and nuts firmly. The torque is dependent on the strength properties of the

stud bolts and the pressure rating of the tank.

6.2 Ambient conditions

6.2.1 Hazardous locations

BM 70 M Ex is suitable for use in hazardous locations of the following zones: 0, 1, 2
Temperature classes T6...T2; danger groups: IIA...IIC

Further information see Section 10

6.2.2 Ambient temperature of signal converter

BM 70 M with horn antenna or Wave-Guide: -20 ... +55°C (-4 ... +131°F)
A BM 70 sunshade should be fitted if the converter is located in the open with the likelihood of

strong exposure to sunlight (see Section 6.1.9).

6.2.3 Flange temperature

Horn antenna, Wave-Guide (T
Horn antenna, Wave-Guide (T

*≤ 50°C):

amb

*≤ 55°C):

amb

High-temperature version with distance piece and

-30 ... +130°C (-22 ... +266°F

-30 ... +120°C (-22 ... +248°F

-30 ... +250°C (-22 ... +482°F) **

FFKM gasket (Kalrez 4079 or Parofluor V3819-

75)
Kalrez 2035 gasket -30 ... +210°C (-22 ... +410°F)
Viton gasket -30 ... +200°C (-22 ... +392°F)
FEP-sheathed gasket -30 ... +200°C (-22 ... +392°F)

* T

is the ambient temperature of the signal converter

amb

** Safety limit: +280°C (536°F)

BM 70 M 21

6.2.4 Ambient temperature limits

Signal converter:

Measuring function OK, but LCD "freezes up"
Functional upper limit, for max. 2 hours

min. - 40°C (-40°F)
max. +70°C (+158°F)

Flange system:

see Section 6.2.3

6.2.5 Storage temperature

-20 ... +60°C (-4 ... +140°F)

6.2.6 Environment class

Locations exposed direct to open-air climate, D1 Severity in conformity with EN 60654-1

6.2.7 Protection category

Signal converter IP 66 / IP 67 (equivalent to NEMA 6)

6.2.8 Shock resistance

The device has been found to withstand the impact test in conformity with EN 61010, Section 8.2,
with 0.5 J energy, and the drop test to prEN 50178:1994.

6.2.9 Vibration endurance limit

Type test conditions acc. to “IACS”

6.2.10 EMC

The devices satisfy the requirements of EN 50081-1, EN 50082-2 and the NAMUR
Recommendation.

6.3 Product conditions

6.3.1 Physical properties of the products

Physical properties (such as density, viscosity, conductivity, relative permittivity, magnetic
properties, etc.) have no effect on measurement results.
The relative permittivity is merely required to have a minimum value in order to ensure reliable
measurements (see Section 6.3.2).

22 BM 70 M

6.3.2 Relative permittivity (

The (relative) permittivity of the product (

εr≥

1.5)

, Epsilon-R) determines the strength of the reflected

ε

r

signal. Measurement results are not affected so long as the reflected signal is strong enough, but
reliability and the maximum measuring range are dependent upon the relative permittivity.

< 3, a stilling well should be used. The minimum relative permittivity of the product is

At

ε

r

approximately

= 1.5. (See also Section 7.5).

ε

r

If the Wave-Stick is also to take measurements when immersed,

Dielectric Constant and Reflection Factor

will need to be > 4.

ε

r

R

70%

60%

50%

40%

30%

20%

10%

0%

1 1.2 1.6 2 2.5 3.2 4 5 6.3 8 10 12 16 20 25 40 50 63 8032

Benzene

LPG Sulfuric acid

Paraffin

Toluene
Petrol
Chlorine

Sulfur

Phosgene

Phenol

Methanol

U S E A B L E R A N G E

Glycol

Nitrobenzene

6.3.3 Product limitations

Radar-based level measuring devices are not suitable for the following products:

liquid ammonia

•

liquid hydrogen

•

liquid helium

•

Water

ε

r

6.3.4 Product temperature (unrestricted)

The product temperature is not a relevant factor, provided the ambient temperature (see 6.2.2)
and the flange temperature (see 6.2.3) are within the specified limits.

6.3.5 Maximum allowable operating pressure

Flange system with horn antenna or Wave-Guide:
PN 16 PN 25 PN 40

DN 80 16 bar (232 psig) --- 40 bar (580 psig)
DN 100 16 bar (232 psig) --- 38 bar (551 psig)
DN 150 16 bar (232 psig) --- 34 bar (493 psig)
DN 200 16 bar (232 psig) 25 bar (363 psig) 32 bar (464 psig)

Information on higher pressures supplied on request.

BM 70 M 23

6.4 Maintenance

Cleaning the antenna

Particular process applications can cause severe contamination of the antenna. Microwaves
cannot be properly emitted or received when reflected from deposits on the antenna. In such
cases, the BM 70 M will usually indicate maximum level (volume) or minimum distance.
The level of contamination at which such errors occur depends firstly on the product concerned,
and secondly on the reflection index, which is mainly determined

E\WKHUHODWLYHSHUPLWWLYLW\0

.

r

Regular cleaning, or use of the purging device (see Sect. 6.1.7), is advisable if the product has a
tendency to form deposits, etc.
When spraying, washing down, or cleaning with mechanical aids, take special care not to
damage either the horn antenna or the bottom Teflon plug at the waveguide window (see Section

7.3 "Field assembly of the BM 70 M"). If cleaning agents are used, take material resistance into
account!

7 Design

Hazardous-duty systems

The BM 70 M-Ex is approved to European Standard EN 50014/18/19/20 for use in hazardous
locations of Zones 0, 1 and 2.

Electronics compartment Flameproof Enclosure "d"
Terminal compartment Increased Safety "e" for signal output and power supply

Optionally: Intrinsic Safety "i" for the signal output and
Increased Safety "e" for the power supply.
Special version: Flameproof Enclosure "d"

Pin coupler compartment Increased Safety "e"
Further details are given in the Certificates of Conformity, see Section 10.

7.1 Dimensions and weights

SA version V96 version

24 BM 70 M

Weights:

Meter size Standard antenna Length Weight
DN (mm) ANSI (“) Type

A (mm)

∅

∅

A (“)

f (mm) f (“) kg lbs
200 8 4 200 7.87 335 19.19 30 66.14
80 3 1s 76 2.99 420 16.54 18 39.68
100 4 2s 100 3.94 620 24.41 19 41.89
150 6 3s 152 5.98 820 32.28 25 55.12
200 8 4s 200 7.87 820 32.28 32 70.55

* Hastelloy: + 30 mm (1.12”)

7.2 Replacement of the signal converter

Always disconnect from power source before commencing work!

Hazardous-duty systems

Before replacing the signal converter (instrument "head") in the hazardous
location, make absolutely certain that there is no explosion hazard (gas-free
certificate). Allow the prescribed waiting time of 27 minutes to elapse before
opening the housing!

1. Remove safety lock (see Sect. 9.3) with machinist's wrench, size 4 mm, and unscrew cover

from the terminal box with the special wrench. If a sunshade is fitted, remove this first (see
Section 6.1.9).

2. Disconnect all cables from the terminals in the terminal compartment, see Section 7.6.

3. Remove the 4 Allen screws M (Allen key size 5 mm) and lift off the signal converter.

The flange unit (incl. waveguide window) will remain tight, also on pressurized tanks.

Caution

On pressurised tanks, do not on any account remove the 4 screws H connecting
the waveguide window to the BM 70 M flange!
DANGER TO LIFE!

4. Install the new BM 70 M signal converter.

5. Check power voltage and fuse(s) (refer to instrument nameplate) and change or replace if

necessary, see Sect. 9.2 and 9.3.

6. Reconnect all cables in the terminal compartment as described in Sect. 7.6.

7. Check against the attached report on settings whether the factory-set parameters are correct

for your application. If not, reset the parameters as described in Sect. 8.

8. Subsequently, record the empty-tank spectrum, see Sect. 8.6.12.

Important

Ensure that the screw thread of the covers on the terminal and electronic
compartments is well greased at all times.

BM 70 M 25

7.3 Field assembly

When the BM 70 M needs to be field assembled, all required parts are included with the

•

supply (stud bolts, washers, etc.).
If supplied loose, bolt the waveguide window (flange assembly) or the distance piece to the

•

BM 70 M. Tightening torque for the 4 Allen screws M (key size SW 5 mm): max. 8 Nm ~ 0.8
kpm.
Note: The upper Teflon plug must be absolutely dry and clean! Moisture and dirt will

•

negatively affect functionality of the BM 70 M!
Bolt antenna and antenna extension together: torque for the 3 stud bolts: max. 8 Nm ~ 0.8

•

kpm.
Do not on any account detach screws H!

•

M

signal converter

distance piece (for
high-temperature version
up to 250°C (482 °F)

O-ring

M

H

BM70 A
connecting flange

antenna extension

upper Teflon plug

O-ring

lower Teflon plug

antenna

7.4 Materials of construction

Check the materials of the antenna, extension, flange, gaskets, and PTFE (contained in all
versions) for compatibility with the product!

7.4.1 Signal converter

Housing stainless steel W 1.4435 (or 1.4539) with electrostatic powder coating.
Sight window borosilicate glass

26 BM 70 M

7.4.2 Flange system

(Antenna, extensions and flange or flange plating)
Available materials for BM 70 M flange systems (in contact with the product):

Version V96 antenna or Wave-Guide:

Material DIN No. AISI equivalent
Stainless steel 1.4571 316 Ti
Stainless steel 1.4435 316 L
Hastelloy C4 2.4610 ­Hastelloy B2 2.4617 -
Titanium 3.7035 ­Tantalum - ­Monell 400 2.4360 ­Inconell 600 2.4816 -

(Information on other materials supplied on request)

Version SA:

Material DIN No. AISI equivalent
Stainless steel 1.4435 316 L

7.4.3 Seals and gaskets

Temperature limitations due to Ex approval; see Part 2 of this installation and operating
instructions.
Responsibility as to suitability rests solely with the user.
Available materials for internal device seals and gaskets in the flange system in contact with the
product:

Version V96:

Material Temperature resistance
FFKM (Kalrez 4079 or Parofluor V8545-75) 250°C/482°F (safety limit 280°C / 536°F)
DuPont Kalrez 2035 210°C/410°F
Viton (FPM) 200°C/392°F
FEP-coated 200°C/392°F

Version SA:

Material Temperature resistance
FPM (Viton) 200°C/392°F
Kalrez 6375

250°C/482°F
(others optional)
PTFE is also in contact with product.

7.5 Process connection

The process connection is by way of standard flanges sized DN 80-200 or equivalent ANSI sizes
(dependent on the version).

BM 70 M 27

7.6 Electrical connection

The electrical connection for supply power and signal inputs/outputs is made in the terminal
compartment (Ex-e) of the signal converter. Observe requirements specified in VDE 165, and
consult the safety advice given in Section 9.4.

In the BM 70 M version with intrinsically safe signal output, only certified
intrinsically safe equipment may be connected to the blue terminals, even if the
device is not operated in the hazardous area!

Terminals conductor cross-section 0.5 - 2.5 mm² (solid conductor: max.

4mm²)
PE safety conductor and/or
FE functional ground
Cable entries 3x M25x1.5 (with standard cable gland: cable clamping area =

Signal cable shielding required for RS 485 line
"Ex" equipotential bonding: U-clamp terminal (max. 4 mm² conductor cross-section) on "neck"

Rated temperature of power cables:

Version Max. flange temperature Rated temperature of power cables
w/o high temperature
distance piece > 100°C/212°F 80°C/176°F
with high temperature
distance piece > 200°C/392°F 80°C/176°F

U-clamp terminal (max. 4 mm² conductor cross-section)

(see also terminal assignments below and in Sect. 9.4)

9-16 mm)

recommended for current output when line lengths > 100 m (350ft)

of signal converter

100°C/212°F

≤

200°C/392°F

≤

70°C/158°F
70°C/158°F

Terminal assignment:

Supply power

NL

Inputs/Outputs

~~

NL

PE

Connections for 115/230 V AC Connections for 24 V DC/AC (any polarity)

28 BM 70 M

12

Inputs/Outputs

+(-) -(+)24V DC

~~

24V AC

Connection of an FE functional ground is not
mandatory

FE

Current output HART®, Ex e: Ex-i current output HART®:

Switching output

max. 100mA/30V DCAC

Current
output

4-20mA

4142

Current
output

32 31

-

+

Ω

Current­output

32 31

-

U min.

= 8V

Digital
input

82 81

-

5...28V=

Ex-i Current output HART
output:

42 41

+

max.500

Switching output

max. 110mA/30V

+

-

®

with switching

+

-

4-20mA

+

32 31

-

+

U min.= 8V

+

4-20mA

-

Ex-i (IS)

supply unit

Current output (non-communicable):

unassigned

+

Current
output

U max.= 30V

32 31

-

+

+

4-20mA

max.250

Ω

-

U max.= 30V

RS 485 version: PROFIBUS-PA or Foundation Fieldbus (FF)

Current
output

BBAA

32 31

-

Ex-i-supply

+

unit

+

32 31

+

Bus-

connection

RS 485

input

RS 485

output

4-20mA

max.250

-

Ω

BM 70 M 29

PROFIBUS-PA / FF with current output: PROFIBUS-PA / FF with switching output:

4-20mA

current

output

42

+

­+

41

U min.

= 8V

-

32 31

Bus-

switching output

max. 110mA/30V

42 41

32 31

connection

Ex-i-supply-

unit

+

U max.= 30V

Bus-

connection

7.7 Terminating resistor for the RS 485 interface

A selector plug on the RS 485 board allows
optionally a high-resistance termination (pre­setting) or a terminating resistor of 120 Ohm at
the RS 485 connections A and B. For this
purpose, the housing (flameproof enclosure) of
the BM 70 M signal converter needs to be
opened (see Sect. 9.3) and the selector plug
turned 180°, see sketch on the right.

RS485 signal-

output board

high-

impedance

120

Ω

....

....

8 User interface

8.1 Local display

In the versions with local display at the BM 70 M signal converter, configuration can be carried
out directly at the device. If a local display is not featured, the PC-CAT program (see Sect. 8.12)
must be used to change the parameter setting (assuming a communicable interface is provided).

The available display is:

Standard display with 2-line LCD display (7 mm high digits for the measured value).

•

Standard display

1 Numerical display of measured value
2 Alphanumeric display of function/unit
3 6 markers to indicate measuring status
4 3 keys for configuration and error inquiry

5 magnetic sensors for control through the

closed housing
(function same as the 3 keys)

6 Compass field, signals actuation of a key

30 BM 70 M