This page is the conditional case for joined cord rings. Mainstream supplier guidance recommends against joined rings in vacuum and in high pressure dynamic service. Where a joined ring is still considered for a static duty, the answer is a test and acceptance path agreed before the ring is made. None of the joint risks on this page applies to compression step moulded rings such as the CO.SM.O range.
The joint, cord section and groove all need review. Pressure may drive the ring towards a clearance gap. Vacuum can expose a small leak path at a poor joint. Dynamic movement can stress the splice over and over. A sound joint in a well supported static gland is a different proposition from a rotating or reciprocating seal.
Ask the supplier to identify the actual joining process and its inspection standard. Check the largest pressure difference, temperature, fluid, flange movement, groove finish and allowable leakage. If failure stops production or creates a safety issue, agree a test and acceptance criterion before the ring is made. A generic pressure rating for all joined rings would be misleading.
If the proposed joint cannot be supported by test or application history, ask about a compression step moulded ring from the CO.SM.O range, or another moulded process, instead. The aim is to make the risk visible before installation, not to reject every joined ring.
Related: large diameter O rings, moulded or joined cord large O rings and the guides library.