Today such check valves are in the form of a separate unit connected to a larger structural unit disposed on the sea bed. The valve housing is provided at each end thereof with a flange, which flange is coupled with a pipeline by means of a connector suitable for the purpose. Thus, in order to mount the valve there is a need for two connectors, one on each side of the valve housing.

Check valves are mainly used in connection with a drilling platform's export pipeline.

The export pipeline may be several kilometers long and contain large quantities of gas.

If a rupture should take place in the riser from the platform or if, in another manner, a leakage should occur on the platform side, the above mentioned check valve has the function of quickly closing in order to prevent gas in the export pipeline from flowing out into the open. Such check valves are generally designed as so-called flapper valves in order to achieve a rapid closure.

In connection with such a check valve there is also placed a by-pass valve having a small cross section. The by-pass valve has the purpose of conducting moderate amounts of gas from the export pipeline and back to the platform. This is necessary because, as a rule, the platform uses gas generators as its most important power source. Therefore, if the export pipeline should be closed off completely, the platform would be without a power supply. This, of course, could not be allowed in a crisis situation, and a specified -- preferably adjustable -- leakage back from the export pipeline is thus necessary.

The existing valves are very expensive structures, however, not least because the replacement thereof is associated with extremely high costs. A check valve of this type is exposed to severe wear and tear, since the valve member will stand and flap in the oil and gas stream and will thereby be subjected to major impact stresses. Therefore, in order to be able to rely on the proper operation of the valve in a crisis situation, the valve must be replaced before the wear and tear has progressed to such an extent that the function of the valve is jeopardized. As a rule, this replacement is done simultaneously with the replacement of the riser between the platform and the export pipeline. This takes place in intervals of about 10 years.

The object of the present invention is to provide a valve which may be replaced in a much more inexpensive and less complicated manner than the existing valves. The present invention also aims to reduce the number of components that are needed in the subsea structure.

The aforementioned objective is achieved by integrating the check valve into a connector in order to join the platfdrm's riser with the export pipeline.

Further, the check valve according to the present invention may also comprise an integrated by-pass valve.

A primary achievement made possible through the solution mentioned above is that when the riser is to be replaced, the check valve will automatically follow along when the connector between the riser and the pipeline is removed. No special, separate equipment is needed to mount and to bring up the valve, since the valve is transported up and down together with the connector by means of the connector's tools. It is necessary to disconnect or to mount only one connector with the replacement of the valve and/or the riser. Due to the fact that there are fewer components, there will also be fewer possible sources of leakage.

The invention will now be described in more detail with reference to the accompanying drawings, wherein: Figure 1 is an elevational view of the connector with an integrated valve, Figure 2 is a lateral, cross-sectional view of the connector with an integrated valve.

Figure 3 is an enlarged section from Figure 2, and Figure 4 is an elevational view of the valve in detail.

Figure 1 shows a connector 1, which generally consists of three parts, a first supporting member 2 and two arms 3 and 4, which arms are connected to respective ends of the supporting member 2 via joints 5 and 6. At opposite ends of arms 3, 4 is a tightening screw 7 mounted for flexible connection at the respective opposite ends of arms 3, 4 in

joints 8 and 9. On the inside of supporting member 2 and arms 3, 4 are clamping jaws 10, which are positioned as segments of a broken circle when the connector is in closed state. On the inside of segments 10 is positioned a seal plate 11, which is supported via a fork 12 by tightening screw 7. Fork 12 is threaded, such that the distance between fork 12 and each of the joints 8, 9 is always the same.

As is best shown in Figure 2, a seal ring 13 is loosely inserted on the inside of the seal plate. In this seal ring 13 there is further inserted a check valve 14. Screwed securely to the supporting member 2 is a grip member 15, which is used by an ROV or other equipment for handling of the connector 1.

The check valve 14 comprises a valve plate 16, in which there is formed a check valve opening 17. A flap member 18 is hinged in a joint 19, to be capable of swinging between a position where flap member 18 closes valve opening 17 and a position where flap member 18 permits free passage through valve opening 17. In valve plate 16 there is also formed a smaller valve opening 20 for a by-pass valve 21.

By-pass valve 21 is best shown in Figure 3. A ball valve member 22 is positioned so as to be capable of selectively opening and closing by-pass valve opening 20. Ball valve member 21 is capable of actuation via a valve stem 23, which is actuatable by an actuator 24 positioned outside the connector, preferably by remote control. Between valve stem 23 and the opening 25 through which it passes in grip member 15 there is formed an annulus 26, in which hydraulic pressure is supplied in order to pressure test the space between seal ring 13 and an O-ring 27. Transverse channels 28 are formed for this purpose.

Seal ring 13, as mentioned above, is loosely inserted in seal plate 11. Further, as mentioned above, valve plate 16 is loosely inserted in seal ring 13. When two pipe sections 29, 30 are to be joined together with the aid of connector 1, these are first brought toward each other inside connector 1. When connector 1 is clamped together around the ends of pipe sections 29, 30 with the aid of tightening screw 7, the flanges 31, 32 of pipe sections 29, 30 first come into contact with clamping jaws 10. Clamping jaws 10 press the pipe sections in toward seal plate 11, or more specifically into the guide edges 33 thereon. When connector 1 is screwed together completely around flanges 31, 32, the end faces of flanges 31, 32 are pressed against the side surfaces of seal plate 11. Only then will sealing contact be established with seal ring 13. Valve plate 16 will not be subjected to any radial pressure worthy of mention, but bears against a shoulder 34 on the inside of pipe section 29. Here there is provided an O-ring 35 to achieve a good seal. If flapper valve 14 closes, it will be pressed further against shoulder 34 and the seal will be even better, without any pressure being exerted by valve plate 16 on seal ring 13.