MRO Magazine

Pump PdM: Infrared helps spot rotating-equipment failures before disaster strikes


March 12, 2012
By PEM Magazine

Pumps, fans, compressors and other motor-driven rotating equipment are essential to manufacturing, commercial and institutional enterprise, from fluid handling systems in petrochemical plants to large air comfort systems in shopping malls.

Many facilities monitor this type of equipment on a regular basis, because often a simple problem like lubrication can be spotted and fixed inexpensively, before the entire unit burns out. Such strategies fall under the general heading of predictive maintenance (PdM).

Thermal imaging is especially useful for monitoring rotating equipment since many impending failures are accompanied by overheating. This predictive technique uses a handheld thermal imager to capture two-dimensional images representing the apparent* surface temperatures of equipment.

What to check?
While it is in operation and under load, monitor rotating equipment that is critical to your operations, i.e., equipment whose failure would threaten people, property or production. Be sure to scan the equipment’s drives — electric motors and gearboxes (if any). Also, on pumps and fans, get thermal profiles of the housings—scans that are likely to reveal any problems with bearings or seals — as well as scans of shaft couplings or drive belts and sheaves.


What to look for?
In general, look for hot spots and pay special attention to differences in temperature between similar units operating under similar conditions. For example, if a bearing in one fan in a bank of similar fans is running hotter than rest, the hotter one may be trending toward premature failure.

On a pump, a difference in temperature along a seal or gasket is the “signature” of a failure. A hot spot on the housing adjacent to a bearing may signal an impending bearing failure, although the root cause probably will not be ascertainable from a thermal image alone.

What represents a “red alert”?
Equipment conditions that pose a safety risk should take the highest repair priority. However, the imminent failure of any critical pump, fan or compressor represents a red alert. Consider using key safety, maintenance and operations personnel to quantify “warning” and “alarm” levels for these assets.

What’s the potential cost of failure?
Because pumps, fans and compressors are key to productivity in so many industries, it is difficult to speak generally about the cost to a company from the failure of a critical unit. However, a failed pump at one automotive facility cost more than US$15,000 to repair while lost labor costs totaled US$600 per minute and lost production opportunities amounted to US$30,000 per minute.

Follow-up actions
Whenever you use a thermal imager and find a problem, use the associated software to document your findings in a report that includes a digital photograph as well as a thermal image. That’s the best way to communicate the problems you find and to suggest repairs. If a catastrophic failure appears imminent, the equipment must either be removed from service or repaired immediately.

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