Vent plugs are commonly installed on Subsea Housings to assist in vacuum testing and dry gas back filling. Highly recommended for larger volume designs to assist in safely removing the end caps by relieving any internal vacuum/pressure buildup. The LBO (leak before open) option has a hole cross-drilled in the threads and through the bottom of the plug to aid with a more rapid release of pressure, while most of the threads remain engaged.
PREVCO’s #4 dual seal vent plug is a modified SAE #4 plug, having an added face seal for increased reliability. The vent port is a standard SAE #4 design with one additional restriction; the spot face sealing surface needs to have a surface finish of at least 32 micro-inches. As most commonly machined ports meet this constraint, our No. 4 dual seal plug can be retrofitted to many existing designs which currently use a standard single seal port. Plugs are available in Stainless Steel (316), Titanium (grade 5), Monel K-500, Copper Beryllium and Inconel 625. Special Materials available upon request. PREVCO’s Leak Before Open Option provides a way for internal pressure begin to escape once the plug is backed out and is no longer sealed yet the threads remain engaged. This is important in cases where there's a concern about the plug becoming a projectile should there be internal pressure inside the underwater housing.