Product Overview

The Bently Nevada 165855-15-CN Cylinder Pressure Transducer is a dynamic pressure sensor for reciprocating compressors. It measures cyclic absolute pressure changes inside a compressor cylinder, allowing engineers to examine pressure behavior throughout the compression cycle and identify deviations from normal operating patterns. The data can support assessments of cylinder performance, valve condition, and changes in compressor operation.

Unlike a conventional process pressure transmitter used mainly for steady-state pressure monitoring, this transducer is intended to capture rapid pressure variations. In natural gas compression, petrochemical processing, and other reciprocating compressor applications, the pressure waveform can reveal operating changes that may not be apparent from a single pressure reading.

The 15 pressure-range option specifies a range of 0 to 172 bar (0 to 2,500 psia) with an armored cable configuration. The CN suffix identifies a country-specific approval option. This combination is relevant when an installation requires the specified pressure range, additional cable protection, and applicable regional approvals.

The transducer operates as part of a complete measurement channel. Its voltage output is acquired by compatible monitoring equipment, where pressure readings can be displayed, trended, and analyzed alongside other machine measurements. For existing installations, replacement selection should account for the pressure range, mechanical connection, cable arrangement, electrical interface, and approval requirements.

Correct installation is particularly important in reciprocating machinery because pressure changes repeatedly over short operating intervals. A suitable pressure port, secure mechanical connection, compatible signal wiring, and correct monitoring configuration all contribute to useful and repeatable pressure data.

Technical Specifications

Product Features

• 172 bar pressure range: Suitable for reciprocating compressor applications where the expected cylinder pressure falls within the specified measurement range.
• Dynamic pressure measurement: Captures rapid pressure changes during the compression cycle for waveform-based analysis.
• Armored cable configuration: Provides additional protection for the cable in demanding industrial installations.
• High-frequency response: Supports pressure waveform measurements up to 5,500 Hz within the specified response tolerance.
• Voltage-based output: Produces a nominal 0.5 V DC zero output and 10 V DC full-scale output for compatible monitoring inputs.
• Defined measurement performance: Specified linearity, hysteresis, and repeatability help establish expectations for measurement accuracy.
• Temperature compensation support: Individual pressure-temperature compensation data can be used with compatible monitoring equipment.
• Country-specific approval option: The CN suffix identifies the relevant approval configuration, which must be checked against site requirements.
• Industrial pressure connection: The 7/8-14 UNF threaded interface supports installation using the appropriate mechanical connection and sealing arrangement.

Working Principle

The 165855-15-CN converts the pressure acting on its sensing element into an electrical voltage. As the pressure inside a reciprocating compressor cylinder changes, the transducer produces a corresponding output signal. The monitoring system acquires this signal and uses it to reconstruct the cylinder’s pressure waveform over time.

The measurement path is:

Compressor Cylinder → Pressure Transducer → Signal Cable → Cylinder Pressure Monitor → Pressure Waveform Analysis

During the compression cycle, cylinder pressure rises as the piston reduces the available volume. Pressure then changes as the discharge and suction valves operate. The shape and timing of these pressure variations provide information about how the cylinder is performing. A waveform that differs from the expected pattern may indicate a valve-related issue, leakage, abnormal loading, or another operating condition requiring investigation.

The 165855-15-CN has a nominal output of 0.5 V DC at zero pressure and 10 V DC at full scale. Monitoring equipment must be configured for the correct pressure range and signal characteristics so that the measured voltage is converted into meaningful pressure values.

Its frequency response extends to 5,500 Hz within the specified tolerance, allowing the measurement channel to capture rapid pressure variations that may be important for diagnosing reciprocating machinery. Actual measurement quality depends on the complete system, including the pressure connection, transducer installation, cable condition, signal acquisition, and monitoring configuration.

Temperature is another consideration. Each transducer is supplied with pressure-temperature compensation data intended to help optimize measurement performance. When used with a compatible Bently Nevada 3500/77M Cylinder Pressure Monitor, the applicable compensation data can be entered into the monitoring configuration to minimize temperature-related measurement effects.

The 172 bar range should be selected according to the expected operating pressure and anticipated transients. A range that is too low can lead to measurement saturation, while an unnecessarily high range can reduce the usefulness of the available measurement resolution for the operating conditions.

Role in a Reciprocating Compressor Monitoring Architecture

The 165855-15-CN provides the pressure measurement at the cylinder level. Its output is passed to the monitoring system, where the pressure waveform can be reviewed alongside other machine measurements to assess operating behavior.

Compressor Cylinder → 165855-15-CN → Signal Connection → Cylinder Pressure Monitor → Diagnostic Software

The transducer supplies measurement data rather than making an independent diagnosis. Alarm processing, trend analysis, and any protective actions depend on the connected monitoring equipment and the configured application.

Industrial Applications

The transducer is best suited to installations where dynamic cylinder pressure is a useful indicator of equipment condition. The selected pressure range, process media, temperature exposure, and approval configuration must match the actual application.

Installation and Maintenance

1. Verify the complete model number: Confirm 165855-15-CN and check that the 172 bar armored configuration matches the intended replacement.
2. Confirm the operating pressure: Ensure that the expected cylinder pressure and anticipated transients fall within the selected measurement range.
3. Inspect the pressure port: Check for contamination, damaged threads, or other defects that could interfere with pressure transmission.
4. Check the threaded connection: Verify the 7/8-14 UNF interface and use the approved installation and sealing procedure.
5. Confirm process-media compatibility: Check that the wetted materials and sealing arrangement are suitable for the gas or fluid being measured.
6. Inspect the armored cable: Check the armor, cable jacket, and connector area for crushing, abrasion, corrosion, or other damage.
7. Verify the temperature conditions: Confirm that the sensor head and electronics housing remain within their respective operating limits.
8. Check the power supply: Ensure that the transducer receives 18–30 V DC with the correct wiring polarity.
9. Inspect the signal connections: Verify connector condition, cable continuity, and secure connections to the monitoring input.
10. Configure the monitoring channel: Set the appropriate pressure range, voltage scaling, channel assignment, and acquisition parameters.
11. Validate the pressure waveform: Compare the measured signal with expected operating behavior and investigate unexpected offsets, noise, or waveform distortion.
12. Document the commissioning results: Record the transducer model, pressure range, wiring configuration, compensation data, and functional test results.

Before removing the transducer, isolate the equipment and depressurize the cylinder pressure connection in accordance with the site’s approved procedures. After installation, confirm that the pressure connection is secure and that the monitoring system displays plausible readings before relying on the data for machinery diagnostics.

Compatible System Components

The 165855-15-CN should be integrated with compatible cylinder pressure monitoring equipment and a suitable signal connection. The monitoring input must support the transducer’s voltage output and configured pressure range.

Recommended Related Models

The following variants belong to the Bently Nevada 165855 Cylinder Pressure Transducer family. The pressure-range and approval suffixes must be checked carefully because they determine the intended measurement range and installation configuration.

Key Advantages

• Measures cyclic absolute pressure changes inside reciprocating compressor cylinders.
• Supports a 0–172 bar pressure range for the specified configuration.
• Captures dynamic pressure variations up to 5,500 Hz.
• Provides a voltage output for compatible monitoring equipment.
• Includes an armored cable configuration for additional cable protection.
• Supports temperature compensation when used with the appropriate monitoring setup.

Technical FAQs

How can the 165855-15-CN help identify a reciprocating compressor valve problem?

The transducer records the pressure waveform throughout the compressor cycle. Changes in pressure rise, valve-event timing, or the overall waveform may indicate abnormal valve behavior. The trace should be compared with the machine’s baseline and interpreted alongside operating conditions before a fault is confirmed.

When should the 172 bar version be selected instead of the 345 bar version?

The 172 bar version is appropriate when the expected cylinder pressure and anticipated transients fit within its specified range. If operating pressure can exceed that range, a higher-pressure variant may be necessary. The selection should consider normal pressure, transient conditions, measurement requirements, and the consequences of signal saturation.

What electrical input does the monitoring equipment need to support?

The transducer provides a voltage output, nominally 0.5 V DC at zero pressure and 10 V DC at full scale. The receiving channel must support the appropriate voltage input and be configured for the 0–172 bar range. A 4–20 mA-only input is not directly interchangeable without suitable signal-conditioning equipment.

Why is pressure-temperature compensation relevant after replacing the transducer?

Temperature changes can affect the transducer’s measurement response. The individual compensation data supplied with the sensor can be entered into a compatible monitoring configuration, such as the 3500/77M, to minimize temperature-related measurement effects. Using the correct data for the installed sensor helps maintain measurement quality.