P R O D U C T

U P D A T E

Cylinder Pressure Transducer
The single most important measurement for con-– the 165855. Its robust construction is built to with-dition monitoring of reciprocating compressors is

stand continuous monitoring of aggressive, in-cylinder

cylinder pressure. Armed with accurate cylinder

environments. In fact, it’s the only transducer of its

pressure at each point in the piston’s stroke, a Pressure-kind (that we’re aware of) with a 3-year warranty.

Volume (PV) curve can be constructed, which provides

It was designed specifically to complement ourindispensable information on the machine’s health.

3500/77M Recip Cylinder Pressure Monitor, ensuring

Historically, in-cylinder pressure measurements werethat this key measurement can be made with themade only intermittently. Even if a transducer wasconfidence that you’re using a robust, fit-for-service

permanently installed on the machine, it was iso-transducer with the same standard warranty duration

lated from the cylinder by using a Kiene valve or

as any other Bently Nevada product. Available in asimilar isolation device. Users would manually open

variety of pressure ranges, from 100 psia to 10,000

the valve, exposing the transducer to in-cylinder con-psia, the transducer provides continuous static andditions whenever measurement data was desired.

dynamic pressure data.

®

Then, they would close the valve again after data
was obtained. Today, however, Bently Nevada has
the transducer technology to deliver continuous,
online cylinder data – technology built to survive
year-after-year in this toughest of all environments,
the inside of a compressor cylinder.

The chemical environments encountered in many
recips have also been carefully considered. Sourgas (i.e., large concentrations of H 2 S), hydrogen,ethylene, chlorides, and other chemicals can destroy
a transducer in a matter of days unless appropriatematerials and construction techniques are employed.

Bently Nevada is pleased to announce the release of

Our new 165855 uses advanced materials, gold plating,a completely re-designed Cylinder Pressure Transducer

and special construction technologies to ensure long,
trouble-free operation in such environments – infact, a patent is being pursued encompassing its
construction and our innovative use of materials.
And, because the sensor is physically segregatedfrom its signal conditioning electronics by a 1-meter
cable, the sensor element can be placed in environments with much higher temperatures thansensors using an integrated design.
Each 165855 is shipped with a calibration curve overpressure and temperature, and this information canbe programmed into the 3500/77M monitor duringconfiguration along with compressor operating
information. This increases the accuracy of the overallcylinder pressure measurement along with derived
measurements which use cylinder pressure. Thesensor is supplied with 7/8-14 UNF threads and aHifluor ™ o-ring to seal between the process gas and42ORBIT1Q04

P R O D U C TU P D A T Ethe outside environment (an ethylene propylene o-adapters supplied by Bently Nevada comply with Society

ring is also included in the packaging and should beof Automotive Engineers (SAE) specification J1926.

used in place of the Hifluor version in ammonia envi-In order to ensure proper sealing of the sensor, theronments). 3/4 NPT and 1/2 NPT adapters are available

SAE J1926 specification must be used for adapters orfrom Bently Nevada, allowing the transducer to beindicator ports that mate directly with the sensor.

used with indicator ports such as Kiene valves having®

these thread sizes (be certain to select indicator
ports and adapters whose materials are compatible

To learn more, download the 165855’s datasheet fromwww.bently.com, or consult your nearest Bently Nevada
sales professional.

with the process gas being used). The sensor and

Cylinder Pressure Transducer Surpasses a BILLION Cycles –and Keeps on Going!
Cylinder pressure measurement in industrial recip-

Testing on the new 165855 has been underway

rocating compressors presents many challenges.

for nearly a year using an apparatus designed to

Cyclic pressure swings inside the cylinder occur
with each revolution of the crankshaft – hundredsof millions of times per year! The cylinder pressure transducer also requires adequate frequency

simulate the cycling inside a cylinder with a discharge pressure of 100 PSIA and an approximate
2-to-1 compression ratio. Not only is the trans-response – on higher-speed recips (near 1200

ducer itself remarkable, but even the test appara-RPM) this will extend beyond 5 kHz. In addition,

tus represents significant innovation – sothe transducer must be relatively immune to dust,

innovative that a patent is being pursued on it asheat, and vibration. And, it must be able to with-well. Recently, the transducer surpassed the 1.1

stand chemical environments that are extremely
aggressive and corrosive – such as H2S.

billion cycle mark while still operating properly –calibration has been re-verified several times dur-The qualification process for our new 165855
cylinder pressure transducer included a carefuling testing and is still within initial specifications.

review of the above specifications. The goal: suchCycle testing will continue until the pressure

specifications would be met with no maintenancetransducer or the test rig fails.

or calibration required for at least three years, andthe transducer would carry Bently Nevada’s standard 3-year warranty. To put this in perspective,

Thorough and rigorous testing such as this helps
ensure Bently Nevada customers have access to

six years of continuous operation for a 300-RPM

the industry’s most robust and reliable cylindercompressor equates to just under a billion cycles.

pressure measurement technology.

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