June 28, 2007 Predictive Maintenance Tip
The only metrics that have any impact outside the maintenance organization itself are those that can be reduced to monetary values.
Management decisions are most easily influenced when the monetary value can be used to justify them. Therefore, Predictive Maintenance (PdM managers must learn to present their cases for predictive maintenance initiation, expansion, continuation and upgrade of tools in monetary terms in order to be successful.
Tip excerpted from “Predictive Maintenance Management” Course workbook by Jack Nicholas Jr. available at
http://www.masteringmaintenance.com
Register for Jack Nicholas’s PdM Managers Web Workshop June 29 - 11 am
June 28, 2007 Vibration Analysis Tip
Frequency Analysis
When there is a problem with the stator in a three-phase induction motor, even a mechanical problem, it will produce an electromagnetic signature. Electromagnetic problems usually involve the stator. Often, the simplest way to check for an electromagnetic problem is to watch the amplitude at the two times line frequency (120 Hz or 7200 CPM) when the power is shut off. If there is an electromagnetic problem, the vibration amplitude will drop off almost immediately. If there is a mechanical problem that does not involve the stator, the amplitude will drop off gradually.
Here is another convenient check. First of all, note the amplitude at two times line frequency in the horizontal position. Instead of leaving the accelerometer in the normal horizontal or vertical position, secure it at the edge of the motor in a tangential position. Now note the amplitude at two times line frequency. If there is an electromagnetic problem affecting the stator, the amplitude at two times line frequency should be considerably higher. This will help to confirm a stator problem.
The reason for this behavior has to do with torque. The 2x line frequency is actually a “torque pulse” frequency. When there is an electromagnetic problem, it will affect the torque. Torque produces a twisting action in motor. Therefore, when the accelerometer is positioned in a tangential location, it will be respond to a change in the twisting action much better that it will, if positioned radially. It will be more sensitive to the torque since it is in a tangential location. The amplitude will be considerably higher at two times line frequency if there is a stator problem.
Tip provided by Dan Ambre, P.E.
Full Spectrum Diagnostics, PLLC
Phone: 763-577-9959
Email:
June 28, 2007 Start Up Tip
The 9th reliability deliverable prior to starting up equipment is “Equipment files (checkout, commissioning, validation documents, engineering drawings and vendor manuals) are intact and readily available to maintenance and operation.” The work is not done until the paperwork is complete and properly filed for easy recall.
Equipment history should be maintained in a well implemented Computerized Maintenance Management System. Engineering drawings identifying equipment, specifications, purchase orders and receipts should link to the equipment in the CMMS. Equipment history starts with the first purchase order. The process to manage this data needs to be understood by all but is recommended to be managed by a maintenance planner scheduler. A planner scheduler has more to gain and lose with through the equipment documentation process.
Tip provided by Kevin Lewton
MetDemand LLC
http://www.metdemand.com
June 28, 2007 Motor Testing Tip
On-line testing and temperature
When doing on-line testing, the parameters that the tester reads change when the machine is cold (recent start-up after long stop period)or when the machine has been running for a period of time. The larger the machine under test, the larger the time for the components (iron, copper and insulation) to reach a stable, operating temperature. Thus, it is important to let the system stabilize for a conservative period of time before running any tests on it.
Among the components of a rotating machine that change due to heat is the Line-to-Line resistance in the copper. This factor alone will introduce an error of about 1% to 2%. On a 5HP motor operating an axial FAN, about 20 minutes are needed before capturing any data.
On the other end, if a machine is submitted to frequent starts and stops the heat build-up will be higher than normal operating temperature. This is due to the stator difficulty on dissipating heat. This would skewed results too. Be mindful of motor (and system) temperatures when testing on-line.
Tip provided by Baker Instrument
Phone: (800) 752-8272 or (970) 282-1200
http://www.bakerinst.com
June 28, 2007 PdM-2007, the Predictive Maintenance Technology Conference & Expo
Please join us for PdM-2007, the Predictive Maintenance Technology Conference & Expo from September 11 through September 13, 2007 in exciting Las Vegas.
This conference is designed for predictive maintenance beginners and seasoned condition monitoring professionals.
This one event provides a venue for all of the techniques and technologies required for reliable machinery operation.
PdM-2007 provides leading techniques and case studies for:
• Vibration Analysis
• Airborne Ultrasound
• Infrared Thermal Imaging
• Motor Testing
• Oil and Wear Particle Analysis
• Other condition monitoring technologies
Register before August 1 and get:
- $70 per night 4 Star Vegas Hotel!
- Save $200 with Early Bird PdM-2007 registration
Call toll free (888) 575 1245 or…
June 28, 2007 Root Cause Analysis (RCA) Tip
When conducting a Root Cause Analysis (RCA) we often start off with the Event being some physical type of failure (i.e. – pump failure, turbine trip, etc.). However, when we reflect on this, what is the real reason that an RCA is being commissioned, because of the physical failure or because of its consequences? When we sit back and think about it, the RCA is often being requested because of some type of business issue. The RCA is not requested because the pump failed, but it is because the failure of the pump resulted in an 8-hour outage? When trying to decide whether you are starting at an appropriate level in your RCA, ask yourself, “What was the consequence of the incident that you were starting at? Asking this question will usually raise you one more level above the failure itself and into the business impact that it had on the organization. In the long run, this will help get the attention of the upper level management for providing support for your recommendations to ensure that the negative business impact does not happen again.
Tip provided by Robert Latino
Reliability Center Inc.
http://www.reliability.com
June 28, 2007 Ultrasound Tip
When Trending bearings, you should never, if at all possible, depend solely on the sound of the bearing.
Why? Because in all likelihood, your hearing and my hearing are not the same.
Tip excerpted from “Now Hear This” by Jim Hall in the June 2007 issue of Uptime Magazine.
June 21, 2007 Predictive Maintenance Tip
The Predictive Maintenance Manager’s Role in Analysis
• Must assure that the predictive maintenance program credibility is not undermined by
-Missed detections
-False Calls or False Alarms
• To this end the maximum number of analysis techniques should be employed to assure accuracy and usefulness of reports from predictive analysis
• Ensure training vendors teach
–Trend Analysis
-Pattern Recognition
-Correlation
-Relative Comparison
-Test against Limits & Ranges
-Statistical Analysis
• Managers should see that analysts learn to use them all
Tip excerpted from “Predictive Maintenance Management” Course workbook by Jack Nicholas Jr. available at
http://www.masteringmaintenance.com
Register for Jack Nicholas’s PdM Managers Web Workshop June 29 - 11 am
June 21, 2007 Vibration Analysis Tip
When performing phase analysis on bearings and couplings, the measurement method and expected results are usually pretty straightforward. However, analysis of foundations may be a little less understood. Roving phase measurements across bolted joints and mechanically fastened components may not be enough to find hidden problems. Consider grouted interfaces, welded frames, and embedded sole plates. It is easy to consider these interfaces as “rock-solid” attachments. Alas, grout can “fracture”, layers of concrete can “de-bond”, welded frames can “crack”, and embedded plating can shift resulting in relative motion. This amplitude of this motion may be minor at the source, but may induce significant response elsewhere. If you don’t physically measure underlying the fault, it is unlikely that you will resolve the problem(s)! When performing phase diagnostics take measurements across every interface; all the way down to where you know the structure cannot be moving…..then take a measurement there too!
Tip provided by Dan Ambre, P.E.
Full Spectrum Diagnostics, PLLC
Phone: 763-577-9959
Email:
June 21, 2007 LubricationWorld-2007
“Mastering Excellence in Machinery Lubrication”
September 11-13, 2007 - Las Vegas Nevada
Please join us for the 3rd Annual LubricationWorld Conference.
Proactive Machinery Lubrication is fundamental for any plant maintenance program, yet most information is locked up with consulting or training companies.
LubricationWorld is an event where lubrication professionals learn from each other through a series of informative learning sessions, short courses, best practices sessions, networking opportunities and a wide selection of full day workshops.
Participants will discover exciting new ideas and learn helpful techniques for machinery lubrication, contamination control, oil analysis, sampling, motor bearings, gearboxes, compressors, synthetic lubricants and more. Co-located with PdM-2007, The Predictive Maintenance technology Conference & Expo.
Register before August 1 for:
- $70 per night 4 Star Las Vegas hotel room
- $200 Early Bird conference registration savings
To request a brochure or register please call toll free (888) 575 1245 or…
