Damage after initial failure

Rohacell 41S, which contains a flame retardant additive, was badly damaged after 371 thermal cycles and therefore the specimen was removed. The initial thermal performance appeared to be excellent, but the structural failures were extensive. 

Various NDE techniques are used to locate defects and flaws in the failed or similar equipment that may not be apparent during the macro visual inspection. An analysis of cracks and other damage during the initiation or progressive phases often provides more information regarding the failure mechanism(s) than the same analysis would at locations where complete failure occurred. Considerable secondary damage to a worn, fractured, or corroded surface may occur after failure. The most common methods of NDE are given below. 

The disease appeared after a latent period of at least one to two weeks, longer in some cases, and an apparent relationship between the extent of use of the oil and the effect (a dose-response relationship) was noted in one report. The syndrome had an initial phase lasting one to two months, with effects mainly on the respiratory system and the accumulation of fluid in the lungs. There were many deaths at this early stage from respiratory failure. In the next phase (two to four months) there was muscle pain and liver damage. In the final phase there was muscle wasting and weight loss and the skin was affected (see box). 

It is important to note that each bag in a set may have a different life as a result of fabric quality, bag manufacturing tolerances, location in the collector, and variation in the bag cleaning mechanism. Any one or a combination of these factors can cause bags to fail. This means that a baghouse will experience a series of intermittent bag failures until the failure rate requires total bag replacement. Typically, a few bags will fail initially or after a short period of operation due to installation damage or manufacturing defects. The failure rate should then remain very low until the... 

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