How incorrect O-Ring installations can lead to failures
How many times have you heard about O-rings being reused? Probably plenty of times. We all may be guilty of reusing packings or seals at one time or another in our maintenance careers. Here is another opportunity to follow standard practices to reduce the number of maintenance errors.
Oftentimes, when we see damaged O-rings, it's because of incorrect installations; however, manufacturing defects can also be a source of O-Ring defects. As a result, we can get O-Rings that are deformed, cut, pitted, or cracked. Some O-Rings have been seen with excess material. Inspect O-rings before installation!
"A simple proactive measure a maintenance technician can take is to make sure that all packings are replaced during routine maintenance and at every overhaul," says Mazeski.
Before installing packings, inspect and lubricate them as specified per the maintenance manual. A caution that is used in engine maintenance is to not use petrolatum in fuel or oil systems. Petrolatum does not easily dissolve in fuel or oil and excessive amounts can cause blockages in small passages that could lead to plugged filters or engine malfunctions. However, if lubrication is used, ensure that the sealing surfaces are clean and free of nicks or scratches.
"Another item that should not be overlooked is the part number of the O-ring," explains Mazeski. "Technicians might use the incorrect O-ring because it looks to be the right size and material. Be sure that the O-ring is in a factory-sealed package and that it is the correct part number."
Also, do not depend on color codes of the O-rings because the codes may vary with the manufacturer. When installing the O-rings, use plastic caps to protect the O-rings from damage caused by the threads. Always push, rather than roll, the O-ring in place because a pre-twist in the O-ring can lead to cracks sooner in service. Do not use sharp tools to install the O-rings. Fingernails can also damage or cut O-rings.
How the lack of proper clamp inspections can lead to failures
Out of Position
One could easily become complacent in clamp inspections. There are hundreds of them to inspect and most of the time they are properly secured. Odds are you won't find a problem. However, if there is a problem, do you know exactly what to look for?
"You need to be very thorough when inspecting clamps," says Mazeski. "It is easy to overlook a broken, worn, or loose one. The moment you do find a bad clamp, take the time to replace it right away because this is another way to prevent more serious problems later. Broken or worn clamps can lead to chafing (or metallic wear) of the tubes, which can lead to loss of oil, fuel, or hydraulic fluid."
During a clamp inspection, a maintenance technician should check the loop clamps for clamp drooping or distress. Check for the condition of the clamp mesh. Is it compacted or deteriorated? Is the mesh missing? If the answer is yes, replace it. That is good standard practice.
Rubber silicone clamps are common and the key inspections are to check for cracks or "chunking" of rubber. Deterioration of the rubber is occurring if you observe evidence of reddish powder around the clamp. When the clamps are removed, check the tube for chafing at the clamp locations. When the clamps are installed, check that the clamps are installed squarely on the tubes. If the clamps are cocked, remove the clamps and check for wear.
The Bottom Line is Safety
Following good standard practices will reduce the number of delays, cancellations, and In-Flight Shutdowns (IFSD) for an operator. Preventing one IFSD could save an airline a significant amount of revenue. Furthermore, the benefits would be to achieve a safety record that is second to none and win the confidence of the flying public.
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