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RELIABILITY
WIRE
Volume 2, Issue #1- January,
2001
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In
this issue |
- New Product Additions to our On-Line Catalog (Now
over 300!)
- Ask the Expert "What
sort of Condition Monitoring data should I collect for my electric
motors?"
- Application
note: "Motor Current
Analysis"
- What's Hot?: New Low Cost
Accelerometer!!
- Case History: System
Integration and Custom Free Standing Cabinets
- Dare to Compare: STI vs.
CEC Vibration Transmitters
- Trivia
Contest: See the Bottom of the Page.
To unsubscribe from the newsletter,
follow directions at the bottom of the page.
|
| New
Product Additions |
The CMCP420VT now comes with a new
optional bright LED display.
RDI now handles a variety of Wilcoxon
accelerometers. Make sure you check us out for the lowest prices
available ANYWHERE on these high Quality sensors.
STI introduces the CMCP604 series
of LOW COST Accelerometer extension cables. They are designed to work
with all Accelerometers using a MIL Spec 5015, 2-Pin connector. The
cable uses a molded Zytel (Dupont) designed MIL Spec. Connector with a
positive seal “0” ring that mates with the MIL-C-5015 connector
found on most accelerometers. The Connector is CE approved and is
designed to be water tight as per NEMA 6P, 13, IEC IP67. The CMCP604
cables are available in three standard lengths of 5, 10, and 20 meters.
Any length desired may be specified and ordered as an option. Cables are
blunt cut.
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| Ask
the Expert: Wolf Campbell, P.E. - SKF Services |
| Question:
"What sort of Condition Monitoring data
should I collect for my electric motors?"
Answer:
Implementation of a vibration based condition monitoring program
where measurements are collected routinely is a large step in determine
the health and condition of your electric motors. These measurements
should at a minimum include velocity readings taken out 10 to 15 times
motor running speed. I suggest supplementing this with acceleration
readings starting at 10 to 15 times motor running speed out to 400,000 cpm
(cycles per minute). These two measurements (velocity and acceleration)
will capture the majority of frequencies of interest. Some of these
frequencies may be due to failing rolling element bearings, imbalance,
misalignment, looseness (both bearing and mechanical), and also electrical
faults that are present. Electrical faults may be due to broken rotor bars
or damaged state slots. Adding specialized readings such as Acceleration
Enveloping (Demodulation) will further enhance the early detection of
faults. In addition to the "traditional" vibration measurements,
monitoring the motor temperature, bearing temperatures, and utilizing
motor current analysis will provide additional parameters that will
correlate with vibration measurements. Ultrasonic or acoustic readings are
also an effective measurement for determining bearing and electrical
condition.
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| Application
Note: Motor Current Analysis |
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Most Data Collector/Analyzers on the market today
have the ability to perform Motor Current Analysis. This method has the
benefits of allowing an indication of motor’s health to be made
non-invasively, while the motor is running under load and in normal
operating conditions.
A clamp-on Current Probe is attached around a
conductor allowing you to measure current without breaking the circuit.
The combination of a Current Probe and Data Collector produces a
spectrum display of motor current which provides you an opportunity to
detect early developing motor problems. With squirrel cage motors in
particular, a significant change in rotor impedance, due to open or
shorted induction bars, appear on your spectrum display as sideband
peaks around the line frequency component. The ratio of sideband
amplitude to the line frequency amplitude provides an indication of
operational performance. At near full load, if this amplitude ratio is
greater than 0.5%, there is some concern of motor malfunction.
A newly installed motor should show minimal
sidebands. Sidebands which appear in use, as with any trend measurement,
indicate something is happening that should be monitored. A
rule-of-thumb alarm value is computed by dividing the overall value by
200. If the amplitude of the sideband peak is greater than this value a
developing early-stage fault should be considered.
Most of the new Condition Monitoring systems
available today have automated the process and some will automatically
generate alarm criteria and condition assessment such as broken rotor
bars, defective castings in die-cast rotors, high resistance joints due
to poor welding or brazing, end-ring fractures resulting from high
thermal and mechanical stresses, and rubbing between rotor and stator
caused by large air-gap eccentricity.
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| What's
Hot? |
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The new CMCP1100 LOW COST
Industrial Accelerometer offers excellent frequency response (0.3
Hz to 10KHz), an integral cable (5,10 or 20 meters), incredibly small size
(1.2" x 1.05") and exceptional price of only $89.00 (with 5
meter cable).
The CMCP1000
is a dual limit, single channel Vibration Monitor with an integral
accelerometer packaged in an explosion-proof housing suitable for NEC
Division I hazardous areas. Designed to comply with API670 standards, the
CMCP1000 far exceeds the capabilities of competitive vibration switches.
The unit also provides a buffered transducer output for detailed
diagnostics. The CMCP1000 provides a local display in terms of velocity
with a full scale range of 0 to 1.0 in/sec.
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| Dare
to Compare: STI vs. CEC Vibration Switch |
|
Looking to upgrade your old, unreliable mechanical
Vibration Switch?. Here is a comparison of two popular models. A review
indicates that the CMCP1000 offers a higher quality product that draws
less current, and provides higher accuracy.
| Specification |
CMCP1000 |
CEC
1-890 & 1-895 |
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| Freq.
Response: |
2
Hz to 20,000 Hz |
5
Hz to 500 Hz |
| Power: |
24
to 32 Vdc |
24
to 32 Vdc |
| |
(35
mA nominal) |
(125
mA nominal) |
| Optional
Filters |
Yes |
No |
| Output: |
4-20mA |
4-20mA |
| Accuracy: |
<
0.5% |
(+/-)
??% |
| Display |
LED,
3.5 Digit |
LCD,
3 Digit |
| Remote
Rest |
Yes |
Yes |
|
Operating
Temperature:
|
-40
to 85C |
-40C
to 85C |
| Buffered
Out |
Yes |
No
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| Special
Offer! |
|
First 100 people that request, will receive a FREE
45 day Trial of the CMCP1100-05 Low Cost
Accelerometer with integral 5 meter cable, or the CMCP420VT Vibration
Transmitter. If not completely satisfied, return within 45 days. If you
keep the unit, you will be invoiced on day 45. Unconditional 45 day
trial - try it - if for some reason you do not like it, simply return
it.
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| Case
History: System Integration - Custom Free
Standing Cabinets |
| A large petrochemical plant
was modernizing it's control room during a plant expansion. STI was
contacted to design and fabricate multiple free standing cabinets to house
Bently Nevada and SKF Condition Monitoring instrument racks. Pre-wired
terminals, power distribution, tagging, ground bars, smoke detectors,
temperature detectors, and other items were provided as required by the
customer. Complete design and drawing packages are furnished in both
AutoCAD and Intergraph. FAT (Factory Acceptance Test) and customer
inspection scheduling were also are provided at the customer's request. To
date, STI has already delivered over 100
integrated custom panels and enclosures to our customers, including
Aramco, BP-Amoco, BHEL, Brown and Root, Caltex, Chevron, Dupont, M&M
Mars, and Wyle Labs. For more information on providing an integrated
instrumentation and HMI (Human Machine Interface) software solution, call
281-334-0766. |
| Upcoming
Trade Shows: |
| Reliability
Direct, Inc. will be sharing a booth with STI
at the 18th Annual Pump Users Symposium March 5-8 in Houston, TX and
at the Power Machinery & Compression Conference March 19-21 in
Galveston, TX. We look forward to visiting with you at both of these
excellent trade shows. |
| Trivia
Contest |
|
The response to the monthly Trivia contest is Great!
Thanks to all of you who are participating. Try your luck at winning
cool prizes!
Question #6 One
important characteristic of induction motors is that the motor runs at a
speed somewhat below the synchronous speed due to rotor slip. The
difference between the synchronous frequency and the motor shaft
running frequency is termed the ______________________.
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with "Remove" in the subject line. |
| Quality
Products at a Competitive Price and the
convenience of secure 0n-line purchasing! |
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