Proximity
Probe System

Interchangeable equipment withservice that’s got you covered.

A rich heritage of expertise.
Proximitor® probe systems based on eddy current technology are commonplacein industrial plants. Wherever a medium or highly critical machine is running,
you’ll likely find non-contacting eddy current systems for condition monitoringmeasurement and/or automatic machine trip shutdown. Baker Hughes Bently
Nevada Proximitor probe system is used to protect and monitor these machines.
From the very first days that Don Bently invented and pioneered the use of theeddy current Proximitor probe in the late 1960s, quality, reliability and ease of use
have been top priorities.
Since 1999, Baker Hughes Bently Nevada product line has manufactured andtested 2 million-plus 3300XL systems. With full access to the statistical processcontrol, Baker Hughes is constantly fine-tuning to provide consistency. Data isbased on serial numbers that go back decades for root cause analysis. That’s
an unmatched level of expertise.

Service that has you covered.
That tradition, rooted in our passion for customer service, is still alive and well.
Today, we’re working hard to provide even better responsiveness and reduced
lead times. Plus, we’ve lowered our expedited and processing fees.

Interchangeable equipment.
And, our Proximity probe systems, which are manufactured in Minden, NV, arefully interchangeable, saving you money and time in spare replacement.

2What doesinterchangeabilitymean?
With Proximity probe systems, the probes, cables, andProximitor® sensors can be easily interchanged without theneed for calibration or special tools.
For example, the most popular line of Bently Nevada
proximity probe systems is the 3300XL 8 mm system.
Interchangeability means that with this system a plantcan easily exchange 3300XL 8mm probes, cables, andProximitors® without any significant change in output such as
gap voltage or direct vibration.
Interchangeability is an important advantage. In the earlydays of eddy current system development, each probe,
cable, and Proximitor had to be tuned to match one anotherin a unique set. Anytime a piece of the system needed tobe replaced, an actual calibrated match was required. This
meant that each vibration point on a machine potentiallyneeded to have its own spare. On a typical four-bearing
machine, the plant might need to stock or calibrate
many different spares—an expensive, complex and timeconsuming endeavor.
SystemColor

3300 XL 5 and 8 mm

Blue

3300 XL 11 mm

Purple3300 XL 25 mm

Lime Green

3300 XL 50 mm

Brown

7200 XL 5 and 8 mm

Light Yellow

3300 XL NSv

Grey

16 mm HTPS

OrangeWhy does that matter?
A Proximitor is a precision instrument, and occasionally it--ora cable--will need to be replaced. Without interchangeability,
unless the plant actually stocked the exact calibrated matchfor the Proximitor or probe cable in need of replacement,
there is essentially no way to replace the part and ensurethat the reading is correct. The plant would need to shut
down the machine, remove the machine covers, and accessthe bearings to be able to replace all three at once—probe,
Proximitor and cable—to ensure the correct reading. In someindustries that may not be an issue. In the critical processindustries where equipment is expected to run for years
without stopping, it is unacceptable.
With a fully interchangeable system like the 3300XL, the plant
simply replaces the damaged Proximitor or cable with anoff-the-shelf spare part and continues to run. No calibrationor special tools required and no need to disturb the probes
installed deep within the machine. In fact, because of
our gold standard and unmatched interchangeability, allmachines at the plant can use exactly the same Proximitor
drivers and cables and, with a few different probe options,the plant’s entire needs can be covered by just a handful of
spare parts shared among all the machines. That means
lower maintenance costs and reduced chance of systemmismatch.

Advantages of interchangeability• No calibration or special tools requiredwith replacement• No need to disturb other probes• Lower maintenance costs• Reduced chance of system mismatch

Baker Hughes Bently Nevada product line Proximitor families

The Bently Nevada product line answered the need for abetter way, pioneering the development of our gold standard
technology that provides complete interchangeability
between the main Proximitor product families. As shown
above, each Proximitor family has its own color-coding foreasy identification.
Baker Hughes uses a metrology-tracked system, so a
3300XL probe purchased 18 years ago works correctly with a3300XL Proximitor module you buy today and an extension
cable you might buy 10 years from now. No one else in theindustry can claim this level of rock-solid performance ANDinterchangeability.

3300XL 11mm
Proximitor probes,
both armored andunarmored cableversions

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The ‘Frankenstein System’ mixing and matching parts
from different manufacturers
A typical Bently Nevada Proximitor, probe, and cable set isengineered to work together as a system.
Companies that mix and match eddy current system parts
from different manufacturers may encounter the so-called“Frankenstein System.” This system mixes and matches parts
from different manufacturers that were never designed towork together. At first, they may appear to work correctly.
However, they soon may begin to have problems.
Case in point: Production was down at a refinery in
the Middle East because critical turbomachinery wasintermittently shutting down. The Bently Nevada system wassuspected of causing false trips. Within hours a local Baker
Hughes field engineer was on site to diagnose the problem.
Upon investigation it was discovered that all of the Bently
Nevada Proximitors had been replaced. Although the Bently
Nevada probes and cables were still in place, the compatible
Proximitor had been replaced with an eddy current driverwith unknown electrical characteristics.

Upon discovering this, the refinery management launched
an internal root cause analysis (RCA) and determined thatthe mismatched eddy current driver was the source of thefalse trips. By changing from the Proximitor with its known
characteristics and replacing it with a competitor’s unknown
product, the plant inadvertently “changed” critical machinery
set points without the plant operators’ knowledge.
Although eddy current systems are relatively easy tomanufacture, they are very difficult to manufacture withrepeatability and accuracy--something the Bently Nevada
product line has done for more than 50 years.
No manufacturer will warranty the mixing and matching oftransducers, which can lead to loss of plant production as
well as unsafe conditions.

Performance plots of 8 mm 5- and 9-meter eddy current system comparison (gap voltage, DSL, ISF): The non-linear
response and error of the mixed system can essentially “change” intended setpoints.

4Setpoints changed outside the process
So how can setpoints be changed without the knowledge of themachinery team? Take this hypothetical example:
1. T
 he plant orders a pair of motor-gearbox-compressors for a
new expansion at the refinery.
2. T he OEM delivers the compressors along with recommended
alarm setpoints for vibration and thrust.
3. Three OEMs are involved: motor, gearbox, compressor.
4. All three OEMs have different recommended setpoints.
5. Plant reliability and consulting engineers have their own desired
setpoints, which are different from the OEMs’.
6. Many meetings between the plant staff and OEM engineers
ensue, and eventually agreement is reached on the initial alarm
setpoints.
7. The installation project is completed.
8. Commissioning is completed.
9. The machine is successfully started, andproduction begins.
10. The operation of the machine has now been handed over tooperations. For any changes to be made to the system at thispoint, an extensive Management of Change Process (MCN)
must now be followed, and for good reason: the amount ofwork that went into determining good setpoints and relay
logic, as well as the risk of lost production or damage to theequipment if an error is made, cannot be over-stated.
11. Fast forward one year. Plant reliability engineers
wish to make a change to a thrust setpoint basedon a catastrophic failure of the same machine at
another plant.
12. The full MCN process then is followed, including many meetings
outlining the reasons for the change. In the end in this case, theplant manager must sign the MCN to allow the change to takeeffect.
If, however, a Proximitor on these machines is replaced with a
non-Bently Nevada driver and the Bently Nevada probes andcables are left in place, this becomes a mixed-system or socalled “Frankenstein System.” The entire process outlined above—
trusted by the reliability engineers, operations, the OEMs, the plant
manager, and even the shareholders—and used to help ensure thesafety, reliability, and financial viability of the operation—has been
inadvertently bypassed. And it was all done because a vendor
stated: “Our eddy current driver is compatible with Bently Nevada
probes and cables.”Even more concerning is that it happened without a substantive
process, evaluation, or the knowledge of many key stakeholders.
Because the gap voltage of the mixed-system still reads essentiallythe same during installation (see gap voltage plots above), theplant in many cases has no realization that its setpoints haveeffectively been changed without process.

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Sample testing shows‘Frankenstein System’ results

Baker Hughes: Keeping youroperations reliable and safe

Some parts manufacturers claim that their eddy current
drivers are compatible with Bently Nevada probes andcables, even to the point of using our own part numbers.
The system will appear to work at first, but often will giveerroneous readings.

1. A void the “Frankenstein System”! Never mix eddy current
systems using parts from different manufacturers.

While the machine is not running during installation the gap
voltage can show similar levels. However, it can be seenclearly in the plots below what happens to the vibration
measurements with a mixed system when the machine
is running. Across the range of gaps in the sample testingthat was done, the vibration in the 9-meter system (shownabove) is generally attenuated, especially above 50 mils ofgap as can be seen in the center plot of incremental scale
factor (ISF). At the extreme gaps the displayed vibration forthe mixed system can be attenuated by 25% or more. The ISF
actually disappears above 80 mils of gap dropping below
150 mV/mil on a system that is supposed to be 200 mV/mil! The 5-meter system that was tested actually shows theopposite, with greatly exaggerated vibration. Without the useof the Bently Nevada gold standard, the other manufacturer’stransducer system has little chance of being within
specification. Depending on each probe and eddy current
driver, the levels could read high or low.
The consequences of the attenuation are more thaninconvenient. If the current vibration reading with a 9-metersystem at a given point on the machine is 6 mil P-P using
another manufacturer’s eddy current driver, the actual
vibration could be in excess of 8 mil PP or more! This could
mean the difference between continued smooth operation
and a costly unplanned outage or even a machine crash.
More concerning than even this is the impact an erroneous
reading has on a critical thrust protection measurement.
Devastating thrust failures can happen within milliseconds,
long before anyone can react. Because of this, many systems
use dual voting or even a Triple Modular Redundant (TMR)
thrust system. The implications of the incorrect scaling of a“Frankenstein System” in this scenario are even worse.

Baker Hughes Bently Nevada
Proximitor and probe designedwith gold standard methods

62. A lways use a genuine Bently Nevada Proximitor productfrom Baker Hughes. Our Proximitor systems are basedon a proprietary gold standard available to no one elseand have high reliability and performance over a wide
temperature range. Our Bently Nevada product line also
holds an unmatched suite of certifications including
hazardous area, intrinsically safe systems, and countryspecific approvals.
3. E
 valuate the Performance. Regardless of what Proximitoror eddy current system is used, fully understand thereliability and accuracy of the system, especiallyover temperature. Refer to industry standards andspecifications such as API 670. Even if you are not in thepetroleum industry, this specification is quite often used
as a general guideline for operating critical rotating
turbomachinery and reciprocating machinery.
4. Keep the Whole System Reliable. Bently Nevada 3300XL
Proximitors, probes and cables, when used together,
form an engineered transducer system that is extremelyreliable. In addition, the Bently Nevada 3500 Machinery
Protection System incorporates all of the Bently Nevada
product line’s 50-plus years of machinery knowledge.
That knowledge has made us exceptional at dataacquisition and at detecting and preventing missed andfalse trips.

Why not an ‘adjustable’ system?

What about various shaft materials?

Some companies claim they can adjust the limits andoutputs of the eddy current system, touting the ability tune
the output to “API standards.” Originally an accepted method,
this legacy approach is no longer needed. Some companies
still rely on it, even advertising it as an advantage, because
they do not have the ability to produce our world-class gold
standard technology.

Real-world machines are provided with a wide range of shaft
materials. Since the non-contacting eddy current system issensitive to the particular alloy of the shaft, the eddy current
sensor must be able to handle these various materials
and provide a consistent, accurate output. Again, somecompanies claim the ability to “adjust” the output of theeddy current system to any shaft material as an advantage.
Unfortunately, they end up in the same situation as outlined
above with a system that is adjustable but may or may nothave been adjusted correctly, leading again to uncertainty.
Or, their system may have had the degradation “adjustedinto it.” Baker Hughes offers a complete library of Proximitors
for common (and uncommon) materials, each with theirown genuine Bently Nevada gold standard so that you do nothave to worry about “tuning” your system in the field.

With more than 4 million Proximitor systems installed on theworld’s most critical equipment, our experience shows that
customers do not benefit from an “adjustable” system.
Firstly, sensors that can be calibrated are often required tobe recalibrated on a scheduled basis. The issue with this isthat there are no calibratable degradation modes in any
eddy current sensors, regardless of the manufacturer. If thesensor scale factor drops, the affected component needs
to be replaced, not recalibrated. Under no circumstances
should an eddy current sensor installed in a machine
be recalibrated due to degradation as this can lead tosignificant measurement error over time, essentially “tuningout” the degradation and blinding the plant to high vibrations
or extreme thrust position.
Another problem relates to troubleshooting and stems
from the fact that once the system has been installed andadjusted, the question always arises about whether or not it
was adjusted correctly. Did the technicians set the correct
upper and lower limits? Was the system adjusted at somelater date? This uncertainty becomes a real issue whena machine begins having a vibration problem. The firstquestion that is asked is whether or not the instrumentation
was “adjusted” correctly. Instead ofBaker Hughes Bently Nevada product line takes the reliability
and safety of your operations very seriously. Over the years
we have labored to earn your trust with your most criticalmachines. These days, we’re working even harder to cover
your service needs with We’ve got you covered with better
responsiveness and reduced lead times, lower expedited andprocessing fees, and longer product life.
In turn, you have come to trust in our solutions and ourexpertise, and the fact that we are committed to nevercompromise when it comes to safety, quality, and reliability.

focusing on the vibration issue, the customer is focused on
diagnosing and/or validating the transducer system! Whena Bently Nevada Proximitor system is used, it requires noadjustment, therefore this uncertainty is removed, and themeasurement can be trusted for shutdown or diagnostics.
Not only do we calibrate our 3300XL Proximity probe systems
to our proprietary gold standard, but our calibration uses
robotics on fully NIST traceable equipment. We have done
this more than 2 million times with the 3300XL…and counting.

3300XL 8 mm and 50 mm
Proximitor probes

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Copyright 2020 Baker Hughes Company. This material contains one or more registeredtrademarks of Baker Hughes Company and its subsidiaries in one or more countries. All
third-party product and company names are trademarks of their respective holders.
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