3500/72M Recip Rod Position Monitor
Datasheet

Bently Nevada Machinery Condition Monitoring

146478 Rev. KDescription
The four-channel 3500/72M Recip Rod Position Monitor
accepts input from proximity transducers, conditions thesignal to provide dynamic and static position measurements,
and compares the conditioned signals with userprogrammable alarms.
Each channel, depending on how you configure it, typicallyconditions its input signal to generate various parameters
called measured values.
Use the 3500 Rack Configuration Software to:lll

Configure alert setpoints for each active measuredvalue and danger setpoints for any two of the active
measured values.
Protect reciprocating compressors by continuously
comparing monitored parameters against configured
alarm setpoints to display alarms and trigger relays, ifneeded.
Monitor the condition of essential reciprocating
compressor machinery.
The monitor channels are programmed in pairs andcan perform up to two functions at a time. For
example, channels 1 and 2 can perform one
function while channels 3 and 4 perform another orthe same function.

The 3500/72M Recip Rod Position Monitor meets API 618
requirements for reciprocating compressors. It measures:lll

Rod position
Rod drop
Hyper-compressor

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Specifications
InputsSignal

Accepts from 1 to 4 proximity
probe signals

Input
Impedance

10 kΩ

Nominal Scale Factor
Rod Position

0.79 mV/µm (20 mV/mil),
3.94 mV/µm (100 mV/mil), or
7.87 mV/µm (200 mV/mil)

Rod Position 2

3.94 mV/µm (100 mV/mil), or
7.87 mV/µm (200 mV/mil)

Rod Drop

3.94 mV/µm (100 mV/mil), or
7.87 mV/µm (200 mV/mil)HyperCompressor

3.94 mV/µm (100 mV/mil), or
7.87 mV/µm (200 mV/mil)PowerConsumption

7.7 watts, nominal

Outputs
Front Panel LEDs
OK LED

Indicates when the Recip
Rod Position Monitor isoperating properly.

TX/RX LED

Indicates when the Recip
Rod Position Monitor iscommunicating with othermodules in the 3500 rack.

Bypass LED

Indicates when the Recip
Rod Position Monitor is in
Bypass Mode.

Front Buffered Outputs
BufferedTransducer
Outputs

The front of each monitor
has one coaxial connector
for each channel.
Each connector is shortcircuit protected.

2/13Output
Impedance

510 ΩTransducer
Power Supply-24 Vdc

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Data Values
The 3500/72M Recip Rod Position Monitor
returns the following data values frommeasurements used to monitor the machine:

Hyper Channel

Position Magnitude,
Position Angle,
Crank Angle,
Rod Position
Pk-Pk Amplitude,
Single Channel Gap,
1X Amplitude,
Not 1X Amplitude,
2X Amplitude

Rod Position
Single 2Channel

Pk-Pk Amplitude
Position Magnitude
Position Angle
Crank Angle
Gap
Average Piston Position
Instantaneous Piston
Position
Instantaneous Probe Gap

Rod Position
Pair Channel

Position Magnitude,Position Angle,
Crank Angle,
Pk-Pk Amplitude,
Gap,
1X Amplitude,
Not 1X Amplitude,
2X Amplitude

Rod Position
Pair 2 Channel

Pk-Pk Amplitude
Position Magnitude
Position Angle
Crank Angle
Gap
Average Piston Position
Instantaneous Piston
Position
Instantaneous Probe Gap

Rod Drop
ChannelAverage Piston Position,
Average Probe Gap,
Instantaneous Piston
Position,
Instantaneous Probe Gap

3/13

Pk-Pk Displacement,
Gap,
1X Amplitude,
Not 1X Amplitude,
2X Amplitude3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Signal Conditioning

Rod Position Single and Pair Channels

Specified at +25ºC (+77ºF) unlessotherwise noted.

Frequency Response

Rod Position 2 (Single and Pair) Channels

Peak-Peakfilter

Fixed 1 Hz to 600 Hz

Gap filter-3 dB at 0.09 Hz

Not 1X filter

Constant Q Notch filter
Minimum rejection in stopband of 34.9 dB overfrequency range of 60 cpm
to 15.8 times running speed

1X and 2X
vector filter

Constant Q Filter
Minimum rejection in
stopband of 57.7 dB

Frequency Response
Peak-Peak filter

Fixed 1 Hz to 600 Hz

Gap filter-3 dB at 0.09 Hz

Average piston
position

Fixed 1 Hz to 600 Hz

Accuracy
Peak-Peak
Amplitude

Within ±0.33% of full-scale
typical±1% maximum

Position
magnitude

Within ±0.33% of full-scale
typical±1% maximum

Rod Position
Angle(paired only)

Within ±1° typical±3° maximum

Position CrankAngle

1X and 2X Vector and Not 1X
parameters are valid for machine
speeds of 60 cpm to 2130 cpm.
Accuracy
Position
magnitude(direct)

Within ±0.33% of full-scale
typical±1% maximum

Within ±1° typical±3° maximum

GapGapWithin ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

1X Amplitude

Average piston
position

Within ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

2X Amplitude

Instantaneous
piston position

Within ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

Instantaneous
piston gap

Within ±0.33% of full-scale
typical±1% maximum

Pk-Pk
Amplitude

Within ±0.33% of full-scale
typical±1% maximumNot 1X
Amplitude

Within ±3.0% of full scale
typicalPosition CrankAngle

Within ±1° typical±3° maximum

4/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Frequency Response

Accuracy
Rod PositionAngle(paired only)

Within ±1° typical±3° maximum

Rod Drop Channels

1X Vector filter

Constant Q filter
Minimum rejection in stopband of 57.7 dB

2X Vector filter

Constant Q filter
Minimum rejection in stopband of 57.7 dB

Frequency Response
Average piston
position(direct)

Fixed 1 Hz to 600 Hz

Average Gap-3 dB at 0.09 Hz

1X and 2X Vector and Not 1X
parameters are valid for machine
speeds of 60 cpm to 2130 cpm.
Accuracy

Accuracy

Peak-Peakmagnitude

Within ±0.33% of full-scale
typical±1% maximum

Average piston
position(direct)

Within ±0.33% of full-scale
typical±1% maximum

Gap

Average Gap

Within ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

1X Amplitude

Within ±0.33% of full-scale
typical±1% maximum

Within ±0.33% of full-scale
typical±1% maximum

2X Amplitude

Within ±0.33% of full-scale
typical±1% maximumNot 1X
Amplitude

Within ±0.33% of full-scale
typicalInstantaneous
piston position
Instantaneousprobe Gap

Hyper Channels
Frequency Response
Peak-Peakfilter

Fixed 1 Hz to 600 Hz

Gap filter-3 dB at 0.09 Hz

Not 1X filter

Constant Q Notch filter
Minimum rejection in stopband of 34.9 dB overfrequency range of 60 cpm
to 15.8 times running speed

5/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

AlarmsPhysicalMonitor Module (Main Board)
Dimensions
241.3 mm x 24.4 mm x 241.8(Height x Width mmx Depth)(9.50 in x 0.96 in x 9.52 in)Weight0.91 kg (2.0 lb)
Alarm
Setpoints

I/O Modules (non-barrier)Dimensions
241.3 mm x 24.4 mm x 99.1
(Height x Width mmx Depth)(9.50 in x 0.96 in x 3.90 in)
Weight0.20 kg (0.44 lb)

I/O Modules (barrier)

Use Rack Configuration
Software to set alert levels
for each value measured by
the monitor and danger
setpoints for any two of thevalues measured by themonitor.
Alarms are adjustable from0 to 100% of full-scale foreach measured value.
However, when the full-scale
range exceeds the range ofthe transducer, the range ofthe transducer will limit thesetpoint.

Dimensions
241.3 mm x 24.4 mm x 163.1(Height x Width mmx Depth)(9.50 in x 0.96 in x 6.42 in)Accuracy ofalarm
setpoints

WeightAlarm Time Delays

0.46 kg (1.01 lb)

Rack Space Requirements
Monitor

1 full-height front slot

I/O Modules

1 full-height rear slot

You can program alarm delays using 3500
Rack Configuration Software.

Environmental Limits

OperatingTemperature

When used with Internal /External TerminationProximitor / Seismic I/OModule:-30°C to +65°C(-22°F to +149°F)-40°C to +85°C(-40°F to +185°F)

Humidity95%
Non-condensing

Alert

From one to 60 seconds in
one second intervals

Danger

0.1 seconds (nominal) orfrom one to 60 seconds in
one second intervals

Timed OK
ChannelDefeatWhen used with Proximitor /Seismic Internal Barrier I/O
Module (InternalTermination)
0°C to +65°C(32°F to +149°F)

Storage
TemperatureWithin 0.13% of the desiredvalue

6/13

OK Channel defeat is
disabled for all Rod Position
and Rod Drop configurations.
As a hyper-compressor
monitor, when bothtransducers are NOT OK, themonitor issues a Danger
alarm immediately.

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Hazardous Area Approvals

Compliance and Certifications

For the detailed listing of country andproduct-specific approvals, refer tothe Approvals Quick Reference Guide(108M1756).

FCC
This device complies with part 15 of theFCC Rules. Operation is subject to thefollowing two conditions:ll

For additional technicaldocumentation, please log in tobntechsupport.com and access theBently Nevada Media Library.

This device may not cause harmfulinterference.
This device must accept any
interference received, includinginterference that may cause
undesired operation.

cNRTLus
When used with I/Omodule ordering
options without
internal barriers

EMC
European Community Directive:
EMC Directive 2014/30/EU

T4 @ Ta= -20˚C to +65˚C (-4˚F to+149˚F)
When installed per drawing
149243 or 149244.

Standards:
EN 61000-6-2; Immunity for
Industrial Environments
EN 61000-6-4; Emissions for
Industrial Environments

When used with I/Omodule ordering
options withinternal barriersElectrical Safety
European Community Directive:

Standards:
EN 61010-1

RoHS
European Community Directive:
RoHS Directive 2011/65/EUMaritime
DNV GL rules for classification – Ships,
offshore units, and high speed and lightcraft
ABS Rules for Condition of Classification,
Part 1lClass I, Zone 2: AEx/Ex nA nC ic[ia Ga] IIC T4 Gc;
Class I, Zone 2: AEx/Ex ec nC ic [iaGa] IIC T4 Gc;
Class I, Division 2, Groups A, B, C,and D (W/ IS Output for Division
1)
T4 @ Ta= -20˚C to +65˚C (-4˚F to+149˚F)
When installed per drawing
138547.

LV Directive 2014/35/EUl

Class I, Zone 2: AEx/Ex nA nC ic IIC
T4 Gc;Class I, Zone 2: AEx/Ex ec nC ic IIC
T4 Gc;Class I, Division 2, Groups A, B, C,and D;

Steel Vessels Rules
Offshore Units and Structures

7/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

ATEX/IECEx
When used with I/Omodule ordering
options without
internal barriers

II 3 GEx nA nC ic IIC T4 Gc;
Ex ec nC ic IIC T4 Gc;
T4 @ Ta= -20˚C to +65˚C (-4˚F to+149˚F)
When installed per drawing
149243 or 149244.

When used with I/Omodule ordering
options withinternal barriers

II 3(1) G
Ex nA nC ic [ia Ga] IIC T4 Gc;
Ex ec nC ic [ia Ga] IIC T4 Gc;
T4 @ Ta= -20˚C to +65˚C (-4˚F to+149˚F)
When installed per drawing
138547.

8/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Ordering Information

Ordering Considerations
llll

For the detailed listing of country andproduct-specific approvals, refer tothe Approvals Quick Reference Guide(108M1756).

For I/O Modules with External
Terminations, order the External
Termination Blocks and cable separatelyfor each I/O Module.
For Internal Barriers, refer to the 3500
Internal Barrier Datasheet (document141495).
The Recip Rod Position Monitor requires
version 3.20 or higher of the 3500 Rack
Configuration Software.
Rod Position Single 2 and Rod Position
Pair 2 channel types require Rack Config
release 6.0 or later.

For additional technicaldocumentation, please log in tobntechsupport.com and access theBently Nevada Media Library.

Rod Position Monitor
3500/72M - AA-BB
A: I/O Module TypeThe lower limit for machine speed is60 RPM in the standard product. For
machine speeds down to 30 RPM,
modification 135M8199-01 is required.

01

I/O Module with Internal Terminations

02

I/O Module with External Terminations

03

I/O Module with Internal Barriers andInternal Terminations

B: Hazardous Area Approval Option
00

None

01

cNRTLus (Class 1, Division 2)

02

ATEX/IECEx/CSA (Class 1, Zone 2)External Termination Blocks
Part Number

9/13

Description

125808-08

Proximitor / Velomitor
External Termination BlockEuro Style connectors

128015-08

Proximitor / Velomitor
External Termination Block
Terminal Strip Connectors

128702-01

Recorder External
Termination BlockEuro Style Connectors

128710-01

Recorder External
Termination Block
Terminal Strip Connectors

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

SparesCablesPart Number

Description

3500 Transducer (XDCR) to External
Termination (ET) Block Cable
129525 - AAAA-BB

176449-08

3500/72M Recip Rod Position
Monitor

A: I/O Cable Length

140471-01

I/O Module with Internal
Terminations

00580434

Internal I/O Moduleconnector header
Euro Style, 8-pin, green
Used with I/O modules
140471-01

140482-01

I/O Module with External
Terminations

135489-01

I/O Module with Internal
Barriers and Internal
Terminations

00580441

Internal I/O Moduleconnector header
Euro Style, 3-pin, green
Used with I/O modules
135489-01 and 140471-01

00502133

Internal I/O Moduleconnector header
Euro Style, 12 pin, blue
Used with I/O modules
135489-01

146479-01

3500/72M Recip Rod Position
Monitor User Manual

166M4363

Connector header
Push-in-spring type
(Alternative for PN 00580441)

166M2389

Connector header
Push-in-spring type
(Alternative for PN00580434)

166M2388

Connector header
Push-in-spring type
(Alternative for PN00580432)

0005

5 feet (1.5 metres)

0007

7 feet (2.1 metres)0010

10 feet (3.0 metres)

0025

25 feet (7.6 metres)0050

50 feet (15.2 metres)

0100

100 feet (30.5 metres)

B: Assembly Instructions
01

Not Assembled

02

Assembled

3500 Recorder Output to External
Termination (ET) Block Cable
129529 - AAAA-BB
A: I/O Cable Length0005

5 feet (1.5 metres)

0007

7 feet (2.1 metres)0010

10 feet (3.0 metres)

0025

25 feet (7.6 metres)0050

50 feet (15.2 metres)

0100

100 feet (30.5 metres)

B: Assembly Instructions
01

Not Assembled

02

Assembled

10/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. KGraphs and Figures

1.
2.
3.
4.
5.
6.
7.

3500/72M Front View
Status LEDs
Buffered Transducer Outputs
I/O Modules Rear Views
Barrier I/O Module, Internal Termination
I/O Module, Internal Termination
I/O Module, External Termination

Figure 1: Legacy Front and Rear Views of 3500/72M Recip Rod Position Monitor

11/13

3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. KThe I/O modules with internal or external terminations have the same jumpers.
Figure 2: Updated Rear View of 3500/72M I/O Modules

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3500/72M Recip Rod Position Monitor
Datasheet

146478 Rev. K

Copyright 2024 Baker Hughes Company. All rights reserved.

Bently Nevada, M2, Proximitor, Velomitor and Orbit Logo are registered trademarks of Bently Nevada, a Baker Hughes
business, in the United States and other countries. The Baker Hughes logo is a trademark of Baker Hughes Company.
All other product and company names are trademarks of their respective holders. Use of the trademarks does not
imply any affiliation with or endorsement by the respective holders.
Baker Hughes provides this information on an “as is” basis for general information purposes. Baker Hughes does notmake any representation as to the accuracy or completeness of the information and makes no warranties of any
kind, specific, implied or oral, to the fullest extent permissible by law, including those of merchantability and fitness
for a particular purpose or use. Baker Hughes hereby disclaims any and all liability for any direct, indirect,
consequential or special damages, claims for lost profits, or third party claims arising from the use of theinformation, whether a claim is asserted in contract, tort, or otherwise. Baker Hughes reserves the right to makechanges in specifications and features shown herein, or discontinue the product described at any time without
notice or obligation. Contact your Baker Hughes representative for the most current information.
The information contained in this document is the property of Baker Hughes and its affiliates; and is subject tochange without prior notice. It is being supplied as a service to our customers and may not be altered or its content
repackaged without the express written consent of Baker Hughes. This product or associated products may becovered by one or more patents. See Bently.com/legal.

1631 Bently Parkway South, Minden, Nevada USA 89423
Phone: 1.775.782.3611 (US) or Bently.com/support
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