A problem seen in dynamic seals, hole crossing damage is a clipping, or shearing away, of part of the pressurized O-ring’s exterior where it crosses a hole or pressure port in a mating surface. It can be caused when the edges of the hole are sharp and / or when differential pressure has unseated the O-ring from its groove, allowing the edge of the hole to clip the O-ring as it crosses. Regardless of the cause, the shearing of the seal compromises the O-ring and leads to immediate failure.

Ideally, the design should be such that the pressurized seal does not have to pass over a groove, port, or hole during service. Barring that, hole crossing damage can generally be avoided by chamfering the edges of the hole in advance. Use of chamfering and correct radiusing will help ensure the O-ring is correctly guided back into its normal squeeze mode as it finishes crossing the hole.

Tough, cut-resistant polyurethane seals should be considered for applications where hole crossing damage may occur. Reducing or eliminating differential pressure will also help lessen hole crossing damage. Concave back-up rings can help restrain the O-ring in its groove to prevent hole crossing damage. Composite rubber-bonded-to-metal seals also prevent the rubber from flowing into the hole as the seal passes by. Figure 134 is an example of O-ring failure due to hole crossing damage.