Manufacturers, rental tool companies, and operators demonstrate that pressure control equipment will not likely fail in service by conducting a hydrostatic pressure test before transporting equipment to the field. Rarely does equipment that meets industry requirements fail in a catastrophic manner. Often, due to a casual approach to tightening bolts, connection leakage occurs, necessitating the retightening of connection bolts. Retightening, sufficient to stop the leak, requires more torque than that required for connections that do not leak on the first test attempt.
Interestingly, an attempt to further tighten a connection that has previously leaked, exactly replicates the phenomenon of subsea connection make-up. The leaking connection has allowed test fluid ( usually water ) to enter the space in the ring groove behind the ring gasket. Further attempts to tighten the connection face the “problem” of the non-compressibility of water. Testing with SRX or SBX gaskets would eliminate this retightening problem, but the higher cost of these gaskets seems prohibitive.
Tip: to produce the same effect as “S” style ring gaskets, “cut” a groove across the I.D. sealing surface of R and BX ring gaskets with a “triangle” file or a small grinding disc. See illustration below.
“CUT” I.D. SEAL AREAS ON RING GASKET TYPES
|TYPE R OVAL RING GASKET||TYPE BX RING GASKET|
|RING GASKETS SHOWN WITH A GROOVE “CUT” ACROSS THE I.D. SEALING SURFACES TO ALLOW TRAPPED FLUID TO ESCAPE|
This groove in the ring gasket, when made deeply enough to remain after ring gasket compression and coining, will allow any water trapped behind the ring gasket to vent to the I.D. bore and eliminate any difficulty in further tightening a leaking connection.
Because RX ring gaskets cost more than R ring gaskets, persons do not usually use RX ring gaskets, unless necessary, for testing equipment that they intend to disconnect and transport before actual use. When equipment connections require RX ring gaskets, these gaskets can have the same type of groove “cut” across their I.D. surfaces producing the same “venting” affect.
Some persons believe the re-use of ring gaskets for testing will save money. Without debating the economics of this issue, WOODCO USA suggests that the Ring Gasket Handling and Inspection Before Assembly section of this web site provides advice that applies as well to inspecting a used ring gasket as a new one, with one exception. A used ring gasket, defined as a ring gasket that has previously sealed a made-up connection, has coined sealing surfaces. The degree of coining depends upon the amount of make-up force previously applied. Ring gaskets must re-coin to seal another connection, so observation of the width of the coined area of any used ring gasket will allow an estimate of its’ suitability for re-use. The wider the coined surface, the less likely the used ring gasket will seal during any re-use. An irregular coined surface, caused by a previous marginal or unusable ring groove connection make-up, renders a ring gasket unsuitable for re-use. 1
Any BX ring gasket previously used in a made-up connection, in which the flange raised faces actually touched together, will almost always fail to test when re-used. 1
Making up ring joint connections of any kind requires considerable effort and uses valuable time, having a connection leak after make-up represents an unnecessary and avoidable waste. It pays to consider all the circumstances involved in any connection make-up situation.
|1||Words in bold italic indicate they have subjective meaning and persons using this information must use experience to improve the reliability of their judgement when the meaning of these words can have impact on performance.|