Joints

Details Joints Joints

1999-02-26

2001-10-09

Nicholson, Eric K. (Department: 3627)

Pipe joints or couplings

With indicator, alarm or inspection means

C285S351000, C285S368000, C073S046000, C277S318000

Reexamination Certificate

active

06299216

ABSTRACT:

This invention relates to joints having seals, and to a system for testing the integrity of the seal of a joint. The invention is particularly applicable to flange joints of a pipeline, for example, and provides a system for testing the integrity of a flange joint without introducing pressure into the pipe work itself of the pipeline.
During the erection or installation of new pipe work, or after modification or maintenance of previously assembled flange joints, the joints will usually require testing for leaks. The present invention is directed towards a system which allows for such testing to be carried out in a safer, quicker and more efficient way. The system will prove the integrity of a joint under test, without hating to enter gas or liquid into the main pipe work of the pipeline.
In addition certain seal configurations according to the present invention allow a high pressure seal to be made to the flange joints with the flange bolts only being subjected to a low torque value.
At present, when a pipeline is assembled, the individual lengths of pipe are provided with end flanges which are bolted to adjacent flanges of adjacent pipes. An annular ring joint seal is provided between the flanges to prevent material, whether it be in solid, liquid or gaseous form, travelling along the pipeline from escaping between the flanges. Often, such ring seals are positioned within opposing recesses formed in the flanges. The flanges are bolted together, thereby applying compression to the ring seal to produce a reliable seal for the flange joint.
In most environments, it is necessary to test the integrity of a flange joint seal. In the off-shore petrochemical environment, it is imperative that flange joints are completely secure, and that hydrocarbons (i.e. in the form of gas or petroleum) passing along a pipeline do not leak from the pipeline. Clearly, if a leak does exist, however small, catastrophic consequences can result. Hence, it is a requirement that all flange joint seals be tested prior to use. Such testing is, at present, extremely time consuming and costly to undertake.
With the foregoing in mind, the present invention aims to provide a novel and inventive joint integrity testing system which is safe, simple to operate and virtually foolproof, without the need to introduce testing material, which can be hazardous, into the main pipeline.
According to the present invention, there is provided a joint comprising a main seal, a secondary seal and a pressure test port providing access to a cavity between the main seal and the secondary seal, wherein the integrity of the main seal can be tested by applying pressure to the cavity via the pressure test port such that the cavity is pressurized and the main seal is tested.
As those skilled in the relevant art will appreciate, the invention requires the provision of a cavity, which is ideally separate from the main pipeline, which involves the main seal such that pressure in the cavity is applied to the main seal. If the secondary (or temporary) seal is between the main seal and the bore of the pipeline, pressure is applied to the secondary seal in a direction which is opposite to that applied to the main seal during normal usage of the main seal. This is something which, as far as the present inventor is concerned, has never before been envisaged in this particular field. Alternatively, of course, in certain flange/joint configurations the secondary seal may be outboard of the main seal.
As will be appreciated, a joint according to the present invention allows, on completion, one operator using equipment which can be hand carried to test the integrity of the joint without introducing hazardous pressure to the bore of the pipeline. Further, the pressure ratings that can be tested range from low pressure to the maximum pressure the flange joint is designed for. Furthermore, although the present invention is particularly applicable to flange joints, in theory it could be used in any environment where a seal is provided between two adjacent surfaces.
Following testing, during normal use of the joint, the secondary seal may be redundant. Indeed, after testing of the main seal, the secondary seal may be destroyed during normal use of the main seal. Such a secondary (or temporary) seal is known as a sacrificial seal.
Preferably the pressure test port, which is accessed from the outside of the joint, is threaded to accommodate a high pressure connector. Furthermore, following testing of the main seal, a blanking plug may be screwed into the threaded pressure test port to close off the port. Alternatively, a pressure gauge, for example, could be applied to enable the pressure in the pipeline to be monitored.
To check the integrity of the main seal, a leak detection port may be included. The leak detection port may communicate with a chamber behind the main seal. Alternatively, the leak detection port may communicate with a chamber defined by the main seal.
The main seal may define two chambers in the joint, the two chambers being joined via a duct through the main seal. As a result, only one leak detection port adjacent the main seal is required.
Preferably the leak detection port is threaded to accommodate a sensor. Following initial testing of the main seal, a pressure gauge or other sensor may be applied to the threaded leak detection port to enable failure of the main seal to be noted, possibly before the main seal fails completely.
If necessary, a bleed port may be provided which communicates with the cavity between the main seal and the secondary seal. If such a port is provided, the cavity may be vented via the bleed port as a pressurising medium, such as a gas, is applied to the cavity via the pressure test port.
In a particularly preferred embodiment, the main seal is an annular seal. It is also preferred that the temporary seal is an “O” ring seal. As mentioned above, however, other shaped seals and general arrangements can be envisaged which do not depart from the scope of the present invention.
The present invention is particularly applicable to a flange joint comprising two flanges, the main seal being held between the flanges. The flanges are also preferably secured together by means of bolts which can be used to compress the main seal between the flanges.
The secondary (or temporary) seal may be positioned within a recess defined between the two flanges.
At least one of the flanges is preferably shaped to receive the secondary seal. If a recess is formed in one of the flanges, the second flange may be a standard flange which has not been modified in any way to cater for a joint according to the present invention. Alternatively, the second flange may include an annular wall for abutting the secondary seal.
In another embodiment, both of the flanges may incorporate recesses for accommodating a respective secondary seal with an annular support wall positioned between the two seals.
The secondary seal, in use, may bear against a support plate. The support plate may be an annular disc defining shoulders for two secondary seals. Alternatively, the annular disc may include a forked edge against which the secondary seal bears during testing of the main seal.
If necessary, a rigid annular ring may be provided outside the secondary seal to support the secondary seal during normal usage of the joint.
The support plate may define a recess for the or each secondary seal.
In another embodiment, the or each secondary seal may be bonded to the support plate.
If a support plate is used, the inside diameter of the support plate is preferably equal to or greater than the bore of each flange. As a result, the support plate will not hinder the flow of fluid through the pipeline itself.
If a support plate is used, the support plate may include surface fins which contact the flanges, during use, to prevent the support plate from moving relative to the flanges after assembly. Indeed, if necessary, the fins may be crushable during assembly to enable sufficient pressure to be applied by the flanges to the main seal. As a result, the support plate is l

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