The present invention relates to a subsea protection cap designed for temporary use on a pipe hub to be installed on subsea located equipment.

During installation work on a subsea structure, such as a subsea compressor station template, many smaller structures are to be lowered from the surface and landed on the template. Such smaller structures may include open ended pipes designed for later connections to equipment or pipes on the template. Each open ended pipe terminates in a pipe hub designed with a standardized flange. Before lowered into the sea, each pipe end is provided with a protection cap, both to prevent damage on the pipe hub and to avoid filling the pipe with sea water. During a lowering operation, pockets of air in the pipes may abrupt expand and create high pressures within the pipe. Such high pressures should preferably be evacuated as soon as they occur. The subsea protection cap is of a new kind that is, as far as we know, not previously known since it is able to act as a pressure relief valve able to evacuate through a full bore opening, thus being able to evacuate high volumes, either it is gas or liquid.

The present protection cap is primarily provided to be able to handle flushing of subsea located pipes. During flushing operations, large volumes of

preservations fluids are forced through the pipes in order to evacuate seawater from the pipes. In such situations, full control of the pressure build ups in the piping is not present. To ensure that the caps are not distorted by the

pressures, some arrangement to release the fluid is needed. What exist today are check valves. These are small and to not manage large volumes unless a large number of valves are used and break discs that provides a possibility to handle large volumes. Break discs, however, leave the pipes open if activated, which in turn results in that the cap needs to be replaced and the piping is filled with seawater again and the flushing needs to be restarted. The present cap enables discharge of large volumes of fluid from the pipes without leaving the piping open for ingress of seawater, since the cap recloses as soon as the pressure drops.

This is solved by a subsea protection cap of the introductory said kind, which is distinguished in that said cap is designed as a full bore pressure relieve valve, which protection cap is arranged with resilient retaining means enabling said protection cap to lift a limited distance from the end surface of said pipe hub when subjected for a predetermined pressure increase within said pipe hub, which limited distance defines a gap between said end surface and said lifted protection cap, able to provide full fluid flow communication from the pipe hub bore and through said gap to the environment.

In one embodiment the cap comprises a main body which is designed with an internal surface arranged to abut and cover the open pipe hub end.

The main body may include a skirt projecting circumferentially from the main body, and the skirt is arranged to be able to straddle over the open pipe hub end. Preferably, though not absolutely necessary, a seal can be arranged on the internal surface of the protection cap to further seal against the pipe hub end. As an alternative, a seal can instead be arranged on the pipe hub end to further seal against the internal surface of the protection cap. In one embodiment the main body can be resiliently retained to the pipe hub by means of an independent fixation and tensioning device. Such independent fixation and tensioning device may include a cap locking bar, which cap locking bar is provided with an operating handle able to turn the cap locking bar to engage with the pipe hub for fixation thereto.

In a preferable embodiment, the cap locking bar is provided with a recessed area enabling the protection cap to be installed onto the pipe hub when the cap locking bar is preinstalled in the protection cap and the recess is facing the pipe hub, and then being able to fixedly lock the protection cap to the pipe hub when the handle is turned.

Preferably the independent fixation and tensioning device can include at least two independent journal means supporting the cap locking bar, which journal means are in turn resiliently supported in the main body.

Each independent journal means may include a projecting and threaded pin onto which the spring package is installed, which spring package is retained between respective washers and at least one nut keeps the spring package in place. The spring package can be adjustable in spring tension, which adjustment takes place by turning the nut on the threaded pin.

In one embodiment the spring package can be a regular coil spring, but preferably is a stack of Belleville springs, which Belleville springs can be stacked either with the dished configuration in same direction, or in alternating direction, which ever provides the required spring characteristics.

In addition, the subsea protection cap may include one or more small size backup valves installed through the protection cap and projecting outwardly, in addition to an ROV operable handle to be able to transport the protection cap through the sea.

In addition, the protection cap may include a regular inlet pipe, which inlet pipe includes a valve, such as a ball valve, able to shot off or open the

communication to the internals of the pipe hub. The subsea protection cap can be made of a metallic material, preferably a lightweight metal, or, as a preferable material, a plastic material, preferably a POM-C material. Preferably each cap locking bar may include a cam mechanism that can be operated by the handle and makes such camming action when turned.

Example of embodiment While the various aspects of the present invention has been described in general terms above, a more detailed and non-limiting example of an

embodiment will be described in the following with reference to the drawings, in which:

Fig. 1 A is a perspective view of a protection cap according to the present

invention installed on a pipe hub;

Fig. 1 B is the protection cap in fig. 1 A in an exploded view;

Fig. 1 C is a view from below of the protection cap in fig. 1 A;

Fig. 2 is a perspective view of an independent fixation and tensioning device; Fig. 3 is a perspective view the independent fixation and tensioning device and part of the protection cap and a large seal to illustrate its location within the cap;

Fig. 4 is a top view of the independent fixation and tensioning device in a shut position;

Fig. 5 is a top view of the independent fixation and tensioning device in an open position;

Fig. 6 is a sectional view of the cam mechanism operated by the handle, and Fig. 7 is a second embodiment of the cap having a substantially circular outer design.

Reference is firstly made to fig. 1A showing a complete subsea protection cap 1 installed on top of a projecting pipe end hub 2. The protection cap 1 is designed for temporary use on the pipe hub 2 during lowering and standby time before final connection to some subsea located equipment. Fig. 1 B and 1 C show in more detail components of the protection cap 1 as they are drawn out of the cap body for illustrative purposes. Fig. 1 A to fig. 1 C should be consulted during the further detailed description of fig. 2-7 to receive a better understanding of the cap 1 construction and the function thereof.

The protection cap 1 is designed as a full bore pressure relieve valve, which means that when it opens to relieve pressure, the opening makes use of the entire flow area of the pipe, i.e. the dimension of the full bore of the pipe or the pipe hub. This means that the evacuation of the pressure happens momentarily. To enable this, the protection cap 1 is arranged with resilient retaining means, as illustrated in fig. 2, which makes the protection cap 1 able to lift a limited distance from the end surface of the pipe hub 2 when subjected for a

predetermined pressure within the pipe hub 2.

The subsea protection cap includes a main body 3, which is preferably made of a light weight material, like a polymer material, such as POM-C. However, aluminum or other suitable light weight metal or material is conceivable.

However, the creeping of a plastic material is a concern that is needed to be taken into consideration when design and dimensions are calculated and made.

The main body 3 includes a skirt 4 projecting circumferentially from said main body 3. The skirt 4 is designed to enter open pipe hub end and includes internal guiding means to easen such entering until they fully mate and abut. The internal surface of the main body 3 is designed to cover and finally abut the open pipe hub end when properly installed. As indicated in fig. 3, a seal 5 is arranged on the internal abutment surface of the main body 3 (only the top surface thereof is shown in fig. 3) to make further sealing against the pipe hub 2 end. As an alternative solution, the seal can be arranged on the pipe hub 2 end instead of internal surface of the main body, or on both if desired.

As mentioned, and with reference to fig. 2, the subsea protection cap 1 is resiliently retained to the pipe hub 2 by means of an independent fixation and tensioning device 6. The independent fixation and tensioning device 6 includes a cap locking bar 7. The cap locking bar 7 is provided with an operating handle 8, which in turn can be maneuvered by a monkey fist 9. The monkey fist 9 is arranged for easy grip by a robot arm on an ROV (not shown). In order to make the monkey fist 9 ready in a standby position, the monkey fist 9 is preferably made buoyant. That robot arm is then able to turn the cap locking bar 7 in order to make engagement between the cap locking bar 7 and a flange on the pipe hub for fixation thereto. The cap locking bar 7 is provided with a recessed area 7a, which recessed area enables the protection cap 1 to be installed onto the pipe hub 2 when the cap locking bar 7 is preinstalled in the protection cap 1 . This is only possible when the recessed area 7a is facing the pipe hub 2 such that the cap locking bar 7 can pass the flange of the pipe hub 2. Then it will be possible to fixedly lock the protection cap 1 to the pipe hub 2 when the handle 8 and the cap locking bar 7 are turned and the recessed area 7a is facing either upwards or downwards.

The independent fixation and tensioning device 6 includes at least two independent journal means 10 supporting said cap locking bar 7. Each journal means 10 is in turn resiliently supported in the main body 3 of the protection cap 1 . Each journal means 10 is resiliently supported in the main body 3 by means of respective spring package 1 1 . The spring package enables respective journal means 10 to yield when the operating handle 8 and associated cap locking bar 7 is turned.

Each independent journal means 10 includes a projecting and threaded pin 10a onto which said spring package 1 1 is installed. Each spring package 1 1 is retained between respective washers 12 and at least one nut 13 keeps the spring package 1 1 in place. Another nut, a lock nut 13a, may be used on top of the first nut to avoid the first nut 13 to turn on the threaded pin 10a.

Each spring package 1 1 is designed to be adjustable in spring tension. Such adjustment takes place by turning the nut 13 on the threaded pin 10a and then lock the nut 13 by means of the lock nut 13a.

Each spring package 1 1 can be a stack of Belleville springs The Belleville springs can be stacked either with the dished configuration in same direction, or in alternating direction, which ever provides the required or desired spring characteristics. Also a coils spring is conceivable, whatever is best suited.

The protection cap 1 includes one or more small size backup valves 14 installed through the protection cap 1 . In addition, an ROV operable handle 15 for transport of the cap 1 can be arranged on the main body 3. The protection cap 1 also includes a regular inlet pipe 16, which inlet pipe 16 includes a valve 17, such as a ball valve with a handle 18. The protection cap 1 can, as mentioned, be made of a metallic material, preferably a lightweight metal, or a plastic material, preferably a POM-C material.

Fig. 4 and 5 are top views of the independent fixation and tensioning device 6 where the recesses 7a, or cut outs in the respective locking bars 7, are clearly shown. When installed into the protection cap 1 , and in the open position of fig. 5, the independent fixation and tensioning device 6 can pass over a projecting pipe hub 2 having an external circumferentially extending flange. Such passing over the flange is made possible due to the fact that the respective recesses 7a in the locking bars 7 are facing towards each other. The handles 8 then indicate "OPEN".

When the protection cap 1 is installed on the pipe hub 2, and in the shut position of fig. 4, the independent fixation and tensioning device 6 cannot pass over the projecting pipe hub due to the external circumferentially extending flange. This is due to the fact that the respective recesses 7a in the locking bars 7 now have been turned 180 degrees and are facing away from each other. The handles 8 then indicate "SHUT". Fig. 6 shows an enlarged sectional view through the protection cap 1 and the pipe hub 2 where the locking bar 7 makes engagement with the flange 2a of the pipe hub 2. More precisely, the cap locking bar 7 includes a cam mechanism 7b which is operated by the handle 8 via the locking bar 7. The cam mechanism 7b is a specially machined surface having a curvature adapted to the inclined circumferentially extending surface 2a' of the flange 2a and is a continuation of the recessed area 7a of the cap locking bar 7. Reference is now made to fig. 7 showing a second embodiment of the subsea protection cap V designed to be installed on top of a projecting pipe hub. The protection cap V is, as before, designed for temporary use on a pipe hub during lowering and standby time before final connection to some subsea located equipment. In this embodiment the outer housing 4' has substantially circular design including some cutouts. Otherwise the respective elements are like the one described together with the fig. 1 embodiment.

The operation of the independent fixation and tensioning device 6 will now be described in connection with fig. 1 to 6, in particular fig. 6.

When the protection cap 1 , with the handles 8 in "OPEN" position, is landed on the pipe hub 2 and the internal surface of the protection cap 1 is abutting the pipe hub 2 end 2b, the seal 5 is sandwiched between those surfaces. In order to make secure engagement of the protection cap 1 to the pipe hub 2, the handles are turned about 180 degrees to "SHUT" position. At some point of such turning of the handles 8, the cam mechanism surface 7b' makes contact and

engagement with the inclined surface 2a' of the flange 2a. By further and continued turning of the handles 8, the cam mechanism surface 7b' makes further and more firm engagement with the flange 2a. When turning the handles 8, the respective spring packages 1 1 , which are seated in the protection cap 1 , are tensioned, and thus the protection cap 1 is retained by a predetermined spring force against the pipe hub 2 end 2b. The spring force of the spring packages 1 1 has to be exceeded before the protection cap 1 is lifted off the pipe hub 2 end 2b to relieve excessive internal pressure. In this way, a full bore relieve valve is obtained.