Grayloc Technology

A Grayloc® connector has three components: a metal seal ring, two hubs and a clamp assembly. The seal ring is a "T" in cross section. The leg of the "T" forms a rib that is held by the hub faces as the connection is made. The two arms form lip seals that create an area of sealing surface with the inner surface of the hub. The clamp fits over the two hubs and forces them against the seal ring rib.

As the hubs are drawn together by the clamp assembly, the seal ring lips deflect against the inner sealing surfaces of the hubs. This deflection elastically loads the lips of the seal ring against the inner sealing surface of the hub, forming a self-energized seal. Internal pressure reinforces this seal, so that the sealing action of the Grayloc® connector is both self-energized and pressure-energized.

In the fabrication of piping systems, less time is required to weld Grayloc® hubs to the pipe since there are no bolt holes to align.

There are only 4 bolts to tighten rather than 8 to 24 as on a conventional flange. The torque required to make up a Grayloc® connection is less than that of a ring joint flange – as much as 75% less. Maintenance is considerably simplified by the fact that removing four bolts will free a connection.

Make and break times are much shorter, usually in the range of three to eight Grayloc® connectors in the same time as one flanged connection. No periodic retightening of bolting is required once the connection is in service. Seal rings can be reused when service conditions allow.

Anything the pipe can take, so can the Grayloc® Connector

When manufactured from the same material as the pipe, the Grayloc® connector surpasses the strength of the pipe and that of most other components.

The rib of the seal ring prevents the seal lip from being crushed by over-tightening. While it acts as a positive stop during makeup, the rib also transfers compressive and bending loads from one hub element to another. The rib has bearing area ample to carry the most severe loading that the piping system can withstand.

Grayloc 3



  • Withstands greater tension loads than conventional ANSI flanges
  • In most cases, withstands more tension loading than the pipe itself
  • In destructive tests, pipe can be loaded in tension to failure without causing the Grayloc connector to leak



  • Numerous independent tests have shown that Grayloc connectors withstand severe bending loads without leaking or loosening
  • In one test, 2'/2" GR 20 Grayloc connector was welded to 2'/2" Sch. XX pipe and subjected to a 2" cold bend, 36" on center - connector did not leak and clamp bolting remained tight



  • In normal piping applications, it is not possible to overload the Grayloc connector or seal ring in compression
  • When very high compressive loads occur, the maximum load on the connector is determined by the limit of the pipe
  • In most cases, the area of the seal ring rib is equal to or larger than that of the cross section of adjoining pipe

Service Extremes

Vibration, heat, cold and thermal shock often accompany service in which psi connectors are heavily loaded. Psi connectors consistently withstand severe situations without routine maintenance. Special designs permit maintenance-free service even under the extreme conditions shown in the table.

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