Electric Motors Archives - Page 5 of 6 - Decatur Industrial Electric

Justification or Nullification

Yes, another tip on justification. At every reliability conference you will hear at least one story where a reliability program is struggling to justify their existence. In one presentation it’s world class performance backed by management and everyone is motivated and every maintenance dollar is linked to a return. Cross the hallway to another presentation and hear about a struggling facility with a “what have you done for me lately” management support, reliability technology used for troubleshooting only, and a poor taste in the mouth of the technician tasked to keep the equipment reliable.

Justification of finds and downtime prevention is very important when you are part of a reliability effort with an existing management team that has been around for a few years. The importance of justification increases to critical when a management change is under way. Don’t wait. Create a basic template for case studies that can be easily documented and shared with existing and new management to prevent the nullification of the reliability effort. Find ways to get management involved in looking at the KPI’s collected such as integrating reliability data into asset management software for dashboard review or ensuring all the technology data acquired can communicate with the latest IOT data analytics package that new management will likely be interested in. New management will be looking for cost cutting opportunities. Case studies to justify a program don’t come every day and take time to collect. Gather accurate information and document finds when the reliability support is good, so you don’t have to jump through hoops to try to save your program when the support is not.

For a look at a variety of case study examples visit our website at http://www.pdma.com/PdMA-case-study.php.

Listening when your Equipment Speaks to You

Do you listen to your motors complaining about overload? Do you see your pump packings crying a flood? Do you hear you bearings whine about contaminated lubricants? Do you notice your steam system that coughs excessive condensate and it’s complains about strained elbows?

There are two types of people in mills. There are people who notice when equipment show signs of distress, and people who don’t. We often call people who don’t see the signs of distress in equipment for “mill blind” people. The mill blindness may not be intentional, but rather a product of being so used to the environment that poor equipment condition just isn’t noticed. Let us supply you with a small informal “mil blindness test for you.

Below are a few examples of “mill blindness” we often see in pulp and paper mills. Most of you have at some point seen these equipment problems before, but ask yourself, are we accepting these conditions or are the problems corrected in our mill?

Continue reading by clicking here.

Band Alarms for Belt Frequency Peaks

When establishing current demodulation band alarms for belt frequencies associated with a 2-pulley belt driven system, remember both the 1x belt frequency and 2x belt frequency should be taken into consideration. Initial band alarms for the 1x belt frequency are recommended at baseline + 10% for caution and baseline +20% for severe. Initial band alarms for the 2x belt frequency are recommended at baseline +25% for caution and baseline +50% for severe. Based on test results from known defects, analysis of the 1x belt frequency focuses more on the system alignment while 2x belt frequency focuses more on belt condition and looseness.

belt frequency

For more information on establishing band alarms for mechanical defects read the short article “Advanced Spectral Analysis” found on the PdMA website.
http://www.pdma.com/pdfs/Articles/Advanced_Spectral_Analysis.pdf

Motor Tripping?

Motor Tripping

After installing a new motor you are experiencing what some call nuisance trips. Are they nuisance trips or is the motor trying to tell you something is really wrong? New doesn’t always mean good. The first thing to do is look for a NEMA Code Letter on the nameplate. This letter will help you calculate the design locked rotor or In-Rush current the motor is supposed to see. Then use the MCEMAX^® 6-channel In-Rush/Start-Up test to see the actual In-Rush current. If the actual current is not exceeding the design current, then you would want to focus your troubleshooting on the trip relay settings.

For details on calculating the locked rotor current from the NEMA Code letter, visit the PdMA website at:

http://www.pdma.com/pdfs/tips/2011/2_21_11.pdf

Motor Testing Tip: Leading and Lagging Indicators

Motor Fault Zones

Leading indicators are those that occur early in the P-F curve while lagging indicators occur later in the failure cycle. Both are key indicators, but it is important to know which one you are dealing with to better diagnose the severity of the situation.

Phase resistance, like infrared thermography, is a leading indicator of power circuit anomalies. Performed at proper intervals you would expect the resistance imbalance to identify early stages of a power circuit high resistance connection. At early stages the effect of a high resistance connection on the motor is minimal and only localized heating occurs. At later stages the current through the affected phase changes resulting in circulating currents in the motor. These circulating currents cause elevated temperatures that may reduce the life expectancy of the insulation system.

Finally, both indicators being on the P-F curve doesn’t mean you have to wait to get to the lagging indicators to make a decision. The general rule of thumb is that the earlier you can correct these issues, without affecting production, the less expensive the repair.

To see a video on the Power Circuit Fault Zone visit the website below at:
http://www.pdma.com/webinars/Power_Circuit_Fault_Zone/powercircuit.html
Thanks to our friends at PdmA for this tip.