If you had a drop of oil on your carport floor immediately under the engine block of your Ferrari, how would you imagine the oil drop found its way to your carport floor? Would you imagine that it splashed out of the dipstick spout? Did it sweat through the engine block? What do you think? Of course you already know the answer. That little drop of engine oil leaked through a gasket seal on the oil pan.

Most square and rectangular shapes in industry require some kind of gasket material cut to seal the odd shape. Most round forms requiring a seal (shafts, sleeves, tubing, threaded joints) use the lowly and shy o-ring. We have o-ring seals all over the house and in the family car. Mechanical seals and instrumentation joints for pumps use a lot of o-rings.

About half of all pumps in the maintenance shop today, were pulled out of service because they were leaking or wouldn’t hold pressure. This is most likely a leaking gasket or o-ring. The o-ring is the rubber component of most pump seals. The o-ring controls the temperature, pressure, and chemical limits of the mechanical seal.

The difference between a mechanical seal in a pump in alcohol service and a pump in steam service is the o-ring. It is not the stainless steel, or the ceramic face of the seal. The difference between a mechanical seal in ammonia service, and a mechanical seal in propane service, is the o-ring. The people who assemble seals install o-rings that are adequate to perform the static pressure and vacuum test, which is normally done with water or air. The ultimate user must verify that the seal elastomers, the o-rings, installed in the factory are adequate for the service application (temperature, pressure, and chemically compatible). If they are inadequate, they must be changed to the correct o-ring rubber compound before the installation. Because most o-rings are black and appear the same, it may be necessary to use an identification tool, or purchase individually packaged and labeled o-rings to identify the o-ring rubber compound. Once the package is opened and stapled shut, the control is lost.