O-ring failure

Not all nuclear accidents are caused by fluid seal failures. However, an article by Stuart Diamond published in September 16, 1986 and reproduced in The New York Times on December 23, 2008, titled Nuclear critics charge reactors and O ring seals pose a threat to safety is worth reading [3]. An excerpt on O ring failures in nuclear plants is given below ... 

A report financed by Public Citizen, a group critical of nuclear power, lists dozens of instances of nuclear plant O ring failures from 1975. For example, faulty O rings at the LaSalle nuclear plant in Seneca, lU., were blamed for the failure of an automatic shutdown system and an emergency cooling system, the report said. 

Scientists, critical of the nuclear industries safety record, say that the seals have been faiUng in nuclear plants hundreds of times during the last decade. As yet none of the failures has caused any very serious accidents, but accidents could well be worsened by an O ring failure. 

Race turning Excessive Out-of-round or Gasket (O-ring) failure... 

The easiest way to prevent many unplanned premature seal failures is to use balanced o-ring cartridge designed seals. Most of the seal manufacturers make models incorporating these design features. 

A more predictable situation exists for an O-ring seal housed as above when contacted and swollen by a liquid solvent. Generally a small amount of positive swell is beneficial to sealing, and it is believed that many seals would not function for long without some swelling. Excessive swelling, however, weakens the seal and leads to total failure by fracture or extmsion. ... 

B. O Ring Joints. The major difficulty with greased and waxed joints is their failure to hold vacuum when exposed to solvents, heat, and some chemicals. For many applications O-joints overcome these limitations. A successful glass Cl-ring joint which is in wide use is illustrated in Fig. 8.3, where it may be seen that both halves of the joint are identical. They mate with an O-ring fitted into a groove, and the two parts are held in place with a clamp. The two halves of these... 

Up Greatly up Stable Random O-ring, membrane failure... 

It is also vital that any other components such as gaskets, O-ring seals, instruments, and other parts are checked for compatibility with the products to avoid failure in service and possible product contamination or equipment downtime for repairs to be made. 

For alloys showing high susceptibility to crevice corrosion, measurements of the pitting potentials are of limited value since failure in service by crevice corrosion would predominate. Polarization measurements can be useful in showing relative susceptibility of alloys to crevice corrosion. Figure 7.46 shows results from cyclic polarization measurements on specimens of three alloys containing O-rings to produce crevices (Ref 66). The environment was aerated water with 3.5... 

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