Even if the edges of the groove have been radiused and the gland thoroughly cleaned, other dangers still exist. The O-ring may have to move across threads, slots, burrs, or other hazards while being installed. In such cases you should place a sleeve, piece of tape, or other buffer between the O-ring and the abrasive surface(s). Beveled-edge chamfers built into the gland design can also assist O-ring placement.

If installation tools are used, care must be taken to avoid damaging the O-ring and prematurely dooming the seal. As a rule, hard and/or sharp instruments should not be used, as they are much more likely to nick or puncture the seal. A common type of damage is “skiving,” or slicing of a seal’s surface (see Figure 92). This can be done by either tools or gland edges and may not become apparent until operation begins. (For more on installation damage, see Diagnosing O-Ring Failure: Installation Damage.) Don’t forget that lubrication is also an essential installation “tool.” Lubrication may be added separately or built into the seal, either as an external treatment or an internal lubricant. Any lubrication must be compatible with all other seal elements.

As a general rule, the O-ring’s I.D. should not be stretched more than 100% during installation. If smaller seals require more than 100% stretch, they should be allowed time to regain their normal size before the gland is shut. Twisting or folding the O-ring may also contribute to spiral failure and should be kept to a minimum. Recall that final resting (service) I.D. stretch should not exceed 5% so as not to compromise the seal’s longevity. The gland itself should be closed with a simple longitudinal motion, without any unnecessary oscillation or rotation that could roll or pinch the seal. You must also exercise due caution during post-use O-ring extraction if the seal is to be reused.

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