mandatory. Ensure that the area used for suchinstallations is clean and free from allcontamination.Remove each O-ring that is to be installedfrom its sealed package and inspect it for defectssuch as blemishes, abrasions, cuts, or punctures.Although an O-ring may appear perfect at firstglance, slight surface flaws may exist. These areoften capable of preventing satisfactory O-ringperformance. O-rings should be rejected for flawsthat will affect their performance.By rolling the ring on an inspection cone ordowel, the inner diameter surface can be checkedfor small cracks, particles of foreign material, andother irregularities that will cause leakage orshorten its life. The slight stretching of the ringwhen it is rolled inside out will help to reveal somedefects not otherwise visible. A further check ofeach O-ring should be made by stretching itbetween the fingers, but care must be taken not toexceed the elastic limits of the rubber. Followingthese inspection practices will prove to be amaintenance economy. It is far more desirable totake care identifying and inspecting O-rings than torepeatedly overhaul components with faulty seals.After inspection and prior to installation,lubricate the O-ring, and all the surfaces that itmust slide over with a light coat of the system fluidor a lubricant approved for use in the system.Consult the applicable technical instruction orNaval Ships’ Technical Manual for the correctlubricant for pneumatic systems.Assembly must be made with care so that theO-ring is properly placed in the groove and notdamaged as the gland is closed. During someinstallations, such as on a piston, it will benecessary to stretch the O-ring. Stretch the O-ringas little and as uniformly as possible. Avoid rollingor twisting the O-ring when maneuvering it intoplace. Keep the position of the O-ring mold lineconstant. O-rings should not be left in a twistedcondition after installation.If the O-ring installation requires spanning orinserting through sharp-threaded areas, ridges,slots, and edges, use protective measures, such asthe O-ring entering sleeve (fig. 7-10, view A). IfFigure 7-10.–O-ring installation.7-11
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