WO2007069911A1

WO2007069911A1 - Smartdump - high pressure side of plug

Info

Publication number: WO2007069911A1
Application number: PCT/NO2006/000484
Authority: WO
Inventors: Jostein Aleksandersen; Harald Syse
Original assignee: Tdw Offshore Services As
Priority date: 2005-12-15
Filing date: 2006-12-15
Publication date: 2007-06-21
Also published as: NO20055964L

Abstract

The present invention regards a method and device for operation of a control system for a plug or elements within a plug, within a pipeline (1), when means for actuation of a device of the control system, are reading the pressure in the external fluid around the plug, at the high pressure side of the plug, and at a given pressure activates the device.

Description

SmartDump - high pressure side of plug

The invention regards a system and method for controlling and operating a device within a removable plug or a removable plug within a pipeline. When using a removable plug within a pipeline for temporarily sealing off the pipeline one needs a system which makes it possible to communicate with elements within the plug to possibly, for instance release the plug. There is with this always challenging to transmitting control signals to the elements within the plug in a safe and secure manner, this being a reliable manner, always making sure the system is responding in the manner one wants and at the same time not inadvertently activate the system when one does not want it to be activated. There is sometime also the challenge of not having the opportunity to operate and or communicate in the most favourable manner.

The plug may comprise at least one fluid operated cylinder, i.e. a chamber with a movable barrier, i.e. a piston movable within the chamber, moved by fluid pressure, for operating the gripping and or sealing means of the plug. The gripping and sealing means are activated to set the plug at the desired location, by gripping the internal wall of the pipeline to fixate the plug and sealing off the pipeline preventing fluid in the pipeline from moving from one side to the other side of the plug when the plug is set. A plug similar to this is for instance described in the applicants own patent application No20023100. The gripping and sealing means may be operated by other elements than a fluid cylinder.

However, the fluid operated cylinder within a plug, for operating gripping and sealing means, must in the case of releasing the plug on a regular basis or in the case of an event, have arrangements or a control system making it possible to release any pressurized fluid within the cylinder, to make it possible to free the gripping and sealing means. Usually there is arranged a dump valve in connection with the fluid chamber. Normally one will have a system within the plug, which system reacts to a specific pressure in the fluid around the plug for activation of the dump valve. This system will be connected to and operated by regulating the pressure in the fluid at the low pressure side of the plug, i.e. the side which is released of pressure when the plug is set. Examples of such systems are described in GB 1 516 671 where it is stated that one controls the pressure on the low pressure side of the plug to deactivated the locking a sealing devices. Prior art describes control systems for self-locking plugs, where the pressure difference across the plug is used to control the releasing of the plugs. This method is also used on the applicants own prior plugs. In these systems it is however the fluid at the low pressure side of the plug which is actively controlled to give the desired pressure difference across the plug, and thereby releases the plug. There are however several problems with having a control system only operated or controlled by the pressure in the fluid at the low pressure side of the plug. One issue is that to prevent this control system to be activated inadvertently this activation pressure is normally a pressure higher than any normal operating pressure in the pipeline wherein the plug is set. The activation pressure will normally also be higher than a pressure the low pressure side normally will experience during transportation in the pipeline to the site to be set and setting. Such an activation pressure may also be a pressure higher than the low pressure side of the plug is capable of handling. When having a gas pipeline and the plug is set a long distance from the pumping equipment it is difficult and will also take a long time to build the necessary pressure in the pipeline on the low pressure side of the plug. This gives that the normal procedure may be dangerous and not applicable to all pipelines, and the procedure may also be costly due to additional time the procedure will take.

There is also a problem in cases where one is setting two plugs after each other in a pipeline to perform work on the section of the pipeline between the plugs. When one has a solution where the high pressure side of the plug is faced away from the other plug one has the opportunity to add a pumping device to create pressure between the plug. However, this needs access to the pipeline and sometimes one does not want to create an access the pipeline in that section. One possible other solution is to bleed fluid through the plug which is both time consuming and sometimes not favourable. Another case is of one is doing work on a pipeline at sea and the water pressure is larger than the pressure of the fluid within the pipeline, then the two plugs are set with their high pressure side facing each other. In this case one will have to build pressure in the whole pipeline on both sides of the section of the pipeline to be worked on, which is really time consuming and in the case of a gas pipeline almost impossible.

It is therefore an aim with the present invention to provide an alternative method for operating the plug or devices within the plug. It is an aim to provide a system and method which avoid some or all of the above mentioned drawbacks with previous know solutions.

The present invention regards a method for operation of a control system for a plug or at least one element within a plug within a pipeline. The plug is inserted into the pipeline, then at position for use, activating the sealing and gripping means of the plug and thereby set the plug. By setting it is meant activating the plug in such a manner that it grips the pipeline wall and seals off the pipeline forming a barrier between two parts of the pipeline, one part on each side of the plug. The pressure in the external fluid around the plug within the pipeline can thereafter be released or increased at one side of the plug and thereby establishing a high pressure side and a low pressure side of the plug. The plug has favorable a configuration making it self- locking with a given differential pressure across the plug. According to the invention means for actuation of a device i.e. the control system, is reading the pressure in the external fluid around the plug at the high pressure side of the plug. The pressure at the high pressure side of the plug is then actively controlled in such a manner that at a given pressure in the fluid at the high pressure side activates the device. Having the possibility of activating a device in the plug as a reaction to an actively controlled fluid pressure on the high pressure side of the plug gives a range of possible operations solving at least some or all of the above mentioned drawbacks with previous known technology.

According to a first embodiment of the method according to the invention the device will be actuated when the means for actuation reads a pressure at a predetermined value. If the pressure is set as a high pressure it will normally be some above the normal operating pressure at the high pressure side of the plug. The high pressure side of the plug is constructed to handle high pressures and there is therefore less chance of failure, and having the possibility of actuating from the high pressure side gives a larger operating range for use of plugs and sets of plugs.

A method as this could reduce time from determination of releasing the plug until it is released if the plug is set with a longer distance from a pump station on the low pressure side of the plug, compared with the high pressure side of the plug. It also gives the opportunity of releasing plugs set after each other without having to bleed through the plugs.

According to a second embodiment of the method the device may be actuated when the pressure on the high pressure side of the plug drops below a predetermined value. This may be favorable to use when the pipeline in question can not handle a larger pressure than normal operating pressure, or there are dangers of the pipeline having a failure when raising the pressure above normal operating pressure.

A third embodiment of the method is to have the control system actuate the device after a given repetitions of fluctuations in the pressure on the high pressure side of the plug, or possibly at a given pressure difference between the high pressure side and another fluid pressure source within the plug or at the other side of the plug. Another possible method according to the invention is where the device is a dump valve for a fluid cylinder which operate the sealing and gripping means of the plug, and the means for actuation of the dump valve is a fluid line connecting the operation of the dump valve with the external fluid, so that the fluid pressure in the external fluid directly operates the dump valve. There may in the means for operating the dump valve also be a control valve or other operating devices.

The device actuated by the method may of course by any other device operated by a fluid pressure, as for instance other kind of valves, transponders, fluid cylinder directly etc. There may also be elements in between the device to be operates and the means for actuation of the device or the external fluid, as protection devices preventing external fluid from entering the internal control system, means for transmitting signals form one source to another etc. The fluid cylinder may be a gas, or liquid operated fluid cylinder. The invention also regards a control system for operation of a plug or at least one device within a plug, when the plug is within a pipeline. The plug comprises sealing and gripping means which preferably are operated by at least one fluid cylinder operated at least partly by the control system. The control system comprises at least one device to be operated and means for actuation of the device. When the plug is set and seals off the pipeline there will when the pressure in the pipeline is let out on one side of the plug be formed a high pressure side and a low pressure side of the plug. According to the invention the means for actuation of the device is operated as a response to an actively controlled fluid pressure at the high pressure side of the ^* plug. According to one embodiment the one device may be a dump valve for a fluid cylinder and the means for actuation comprises a fluid line connecting the operation of the dump valve with the external fluid at the high pressure side of the plug. The means for actuation may comprise a control valve operatively connected to the dump valve, which control valve is in connection with the external fluid around the plug on the high pressure side of the plug and is operated as a response to the pressure in the external fluid. The means for actuation may in other embodiments comprise a transducer or similar device, reading the pressure and then transmitting signals to operate the device.

The means for actuation may in another embodiment use the pressure at the high pressure side of the plug together with pressures within the plug and or on the low pressure side of the plug, giving that it is the pressure difference between these places that actually actuates the device. The high pressure side may act against a back pressure in the control system, where the back pressure may be an internal pressure or the pressure on the low pressure side of the plug, by for instance arranging a slide valve reading the pressure on the high pressure side of the plug on one side surface of the slide element and another pressure on the opposite end surface of the slide element, this may of course also be equipped with devices preventing it from being actuated before a given pressure at the high pressure side is achieved or combined with principles of actuation as described in the applicant's own simultaneously filed application NO 2005 5965

The invention will now be exemplified with a non-limiting embodiment shown in the enclosed figure.

A plug 2 is positioned within in pipeline 1. The plug comprises sealing means 3 and gripping means 4. The sealing means 3 is a circumferential packer which expands in a radial direction to seal against the inner pipeline wall. The gripping means 4 is in this embodiment several slips arranged around the circumference of the main body of the plug, which slips are wedged outwards against the pipeline wall by a at least partly cone shaped sleeve or part of the main body arranged at the inside of the slips. These are operated by a hydraulic cylinder (not shown) within the plug, the hydraulic cylinder draws two end plates of the plug together and thereby presses the slips outwards and the packer into contact with the inner pipeline wall. The packer of the plug will with such a configuration of sealing and gripping means, normally be positioned close to the high pressure side of the plug. The plug with such a configuration of gripping and sealing means will also normally have a self-locking effect as a consequence of a pressure different between the two sides of the plug. The hydraulic cylinder is centrally positioned within the plug. There is to the plug attached a control module 6. There is to the control module attached a dump valve 10 connected to the hydraulic cylinder, the dump valve 10 is by actuation means in this embodiment a direct line 12 to the external fluid, operated in response to the pressure at the high pressure side of the plug 2.

The invention has now been explained with an embodiment. A skilled person will be able to make several alterations and modifications to the embodiment within the scope of the invention as defined in the following claims.

Claims

1. Method for operation of a control system for a plug or elements within a plug, within a pipeline (1), wherein the plug is inserted into the pipeline (I)₅ then set at position for use by operating sealing and gripping means (3,4,) of the plug, then releasing the pressure in the external fluid at one side of the plug and establishing a high pressure side and a low pressure side of the plug, when means for actuation (10) of a device of the control system, are reading the pressure in the external fluid around the plug, at the high pressure side of the plug, and then actively controlling the pressure at the high pressure side of the plug for activation of the device at the desired moment.

2. Method according to claim 1, wherein the control system actuates the device when it reads a pressure above a predetermined value.

3. Method according to claim 1, wherein the control system actuates the device when the pressure drops below a predetermined value.

4. Method according to claim 1, wherein the control system actuates the device after a given repetitions of fluctuations in pressure on the high pressure side of the plug.

5. Method according to claim 1, wherein the device is a dump valve for a fluid cylinder, which cylinder is pressurized to activate the sealing and gripping means to an extended position in contact with the pipeline wall, and the means for actuation of the dump valve comprises a fluid line connecting the operation of the dump valve with the external fluid, so that the fluid pressure in the external fluid directly operates the dump valve.

6. Control system for operation of a plug or devices within a plug, within a pipeline, which plug comprises sealing and gripping means which are operated at least partly by the control system, which system comprises at least one device and means for actuation of the device, and when the plug is set there will be formed a high pressure side and a low pressure side of the plug, wherein the means for actuation of the device is operated as a response to a actively controlled fluid pressure at the high pressure side of the plug.

7. Control system according to claim 6, wherein the one device is a dump valve for a fluid cylinder preferably operating the gripping and sealing means of the plug, and the means for actuation comprises a fluid line connecting the dump valve with the external fluid at the high pressure side of the plug.

8. Control system according to claim 7, wherein the means for actuation comprises a control valve operatively connected to the dump valve, which control valve is in connection with the external fluid around the plug on the high pressure side of the plug and is operated as a response to the pressure in the external fluid.

9. Control system according to claim 6, wherein the means for actuation comprises a transducer or similar device, reading the pressure and then transmitting signals to operate the device.