The invention relates to a safety device for gas pipelines for preventing calamities, in particular by drillings for natural gas and gas pipelines interconnecting production platforms mutually or with the shore.

Gas pipelines are usually enclosed by a concrete jacket, and are provided with a system of valves, intended for adjusting and controlling the product flow. if a calamity occurs therein, such as by corrosion, poor welding or the like, ^' or by outside causes which may occur intentionally or unintentionally, this will cause not only a serious loss in production, but also a pollution of the environment. If this is accompanied by a fire at a surface section of the pipeline, said surface section will be seriously damaged. In some instances it will even be no longer possible to make future use of the surface section, thus causing a substantial loss in capital as a consequence.

If gas is released from a pipeline on land the risk of damages is substantial, as it will easily ignite in contact with the air. In order to control such a fire it is present practice to separate the discharging gas from the air; to that end complicated and usually expensive techniques are available. The same applies for off-shore gas pipelines if the free discharge of the gas occurs above the surface of the water. If it occurs below the surface of the water, no fire will occur, but a serious pollution of the water will affect rather wide surroundings, while blocking of the free discharge will be possible only under very difficult conditions and accordingly at high expense.

An additional factor is the period of time that the use of the pipeline will.be stagnated. This may range

from a number of days to a number of weeks for large calamities and in some instances will even result in a permanent termination of the use of the pipeline.

Accordingly it would be desirable to have a safety device allowing to stagnate the gas flow completely or at least largely as soon as a calamity is detected and will also allow the gas flow to be resumed at short notice .

To that end the present invention provides a safety device, comprising an inflatable bag, confined to a predetermined expansion area by a reinforced fabric, connected by means of a pyrotechnical device with a high pressure vessel, as described in more detail hereaf er.

An obvious solution would be to provide a valve in the pipeline, which can be operated by remote control. However, the customary stop valves, whether ordinary valves, sliding valves, diaphragm valves or the like, all comprise movable parts and sealings, exposed to the effects of the environment. As a consequence thereof such a device will frequently be defective in function- ing at the required moment in time, for example by cor¬ rosion, in particular after having been installed for a extended period of time. Though it is actually possible to provide such a device with a jacket, capable of completely excluding attack from the outside, reqμired inspections of such devices at regular intervals will then be a very complicated matter.

The present invention now provides a safety device for closing a pipeline completely or at least largely, that is maintenance free and can still provide its closing function on command, such as by optionally coded remote control signal, suitable for pipelines of customary

diameter, usually up to about 1 meter in diameter, comprising^ pyrotechnical device, an inflatable bag and a high pressure vessel as mentioned above. The closing action of the safety device according to the invention may act either from the outside or from the inside on the gas pipeline. Thus the safety device may either be present around a pipeline of customary diameter or alternatively it may be conveyed to the affected area inside the pipeline.

For action from the outside it will comprise a pipe element of an elastomer material, having the same diameter as the pipeline, provided with at least one set of diametrically opposed inflatable bags in an area.. immediately surrounding said pipe element, each bag being provided with a surrounding confining reinforced fabric, limiting the area to which the bag may expand, the area in which the bags are positioned being restric¬ ted by the inner wall of an annular pressure vessel, each bag being connected with said pressure vessel by means of a pyrotechnical device, said pressure vessel containing a high pressure inert gas, suitable for the purpose. The pressure vessel may, if desired be surroun¬ ded longitudinally by a concrete jacket. The pyrotechni- cal device can be broken by an appropriate signal, preferably coded to avoid unintentional triggering of said device, thus allowing high pressure gas to fill the inflatable bags, which in turn will then deform the flexible pipe element, thus blocking flow through said pipe element completely or at least largely. If required or so desired, a number of sets of inflatable bags may be used, positioned in longitudinal succession along the pipe element, in order to squeeze the gas flow. Dependin on the total length of the pipeline to be thus protected against major calamities, one or more of these safety devices will be desirable. As the safety device is pro¬ vided with suitable connecting means, such as for exampl flanges, it is easy to install in both newly laid and

existing pipelines.

Alternatively the safety device can cause blocking of the pipeline from the inside by conveying a pigg of adequate dimension through a pipeline to a position near that but upstream of the calamity. The pigg will then comprise a pressure vessel, connected by a simila pyrotechnical device to an inflatable bag, confined to a predetermined area by a reinforced fabric, the dimensions of the pigg being such to allow free passag of the pigg through te pipeline on the one hand and substantially complete closing of the pipeline after triggering the pyrotechnical device on the other hand by thus expanding the inflatable bag surrounding the pressure vessel within the confinement of the reinforc fabric. For a pipeline of considerable length a plural of piggs will be required to guarantee quick and appropriate action in case of a calamity. Optionally an additonal pyrotechnical device of different trigger signal (preferably coded) may be provided for release of the gas pressure in the bag, thus restoring free flow again after the required repair of the pipeline has been completed, both for the pigg and for the external positioning of the bags. If piggs are used the pipeline is preferably provided with at least one but preferably a plurality of ports, at least one at both ends of the pipeline, in order to introduce into to remove from the pipeline any pigg if so desired.

The invention will now be elucidated by means of the accompanying drawings, wherein

Fig.l shows the upper half of a safety device according to the present invention in open position, suitable for action from the outside, the lower half being the mirror image,

Fig.2 shows similarly the safety device according to Fig.l but now in the "closed" position,

Fig.3 shows another safety device according to the inve tion in open position, suitable for action ^" from the

ins ide , and

Fig.4 shows similarly the safety device according to

Fig.3 in the "closed" position.

Fig.l showing the upper half of a pipe element in a pipeline in open position, shows a clamping ring 1 fitting over a reinforced fabric envelloping an elastomer tube 3. A pyrotechnical device 4, capable of being triggered by remote control, such as a rupture plate, is fitted on an inflatable bag 5, which is to a ^* ct as a compression bag, the other side of the pyrotechni¬ cal valve 4 being connected with a pressure chamber 7 inside annular pressure vessel 6. The pressure vessel 6 is hermetically sealed on a pipeline 9, e.g. by welding. The said pipeline 9 is fitted with connecting means 8, which allow connection with the main pipeline. The flexible tube 3 has substantially the same diameter as the main pipeline. Chamber 7 is filled with a suitable inert gas, such as for example nitrogen, preferably with as low as possible oxygen content. The flexible tube 3 is tightly ans securely connected to the steel piping, being vulcanized thereto, thus providing a gas tight assembly .

Fig.2 shows the upper half of a pipe element in a pipe¬ line as shown in Fig.l but now in closed or at least largely closed position, the same reference numbers relating to the same parts.

Fig.3 shows a pigg 10 inside a conventional pipeline 11 comprising a pressure vessel 6' provided with a pyrotech¬ nical device 4 connected on its other side with an inflatable bag 5', said bag being surrounded by a continuous reinforced fabric 2" . The pigg 10 will be conveyed through the pipeline 11 just like any conventional pigg.

Fig.4 shows the pigg 10 according to Fig.4 in closed position, i.e. after triggering the pyrotechnical device 4, thus pushing the bag with its surrounding reinforced

fabric against the inner wall of the pipeline 11.

In Fig.l the pressure inside the flexible elastomer tu 3 amounts to the customary pressure in the pipeline of some 70-100 bar, the diameter of the pipeline being some 50-100 cm. The pressure in the inflatable bag is then about 1 bar, while the pressure in the pressure chamber 7 amounts to some 200 bar.

In Fig.2 the pyrotechnical device 4 has been broken by a suitable signal, such as emitted with a suitable wave length from a suitable source or alternatively by a wir connection to a command post, from where the required explosion can be triggered. The passage of such a cable through the jacket may however have a disadvantageous effect on the corrosion and explosion resistance of pressure vessel 6. As shown herein the inflatable bag 5 will then expand within the limitation set by the rein¬ forced fabric, the pressure in the pressure chamber 7 and inside the inflatable bag 5 reaching an equilibrium somewhat below the initial pressure in -.the; ^" . ressure chamber 7, but still well above the pressure in the mai pipeline of at most some 100 bar, thus high enough to compress the flexible elastomer tube 3, which if desire may be reinforced with Twaron or Kevlar fibre, thus preventing the flexible tube 3 from expanding beyond the desired diameter, while not hampering compression of said tube 3. Thus the desired effect is provided. Optionally the pressure chamber may be provided with an additional pyrotechnical device of different trigger ing wavelength (preferably coded), which might be used to release the gas pressure in the bag after completed repair, thus restoring free flow again in the pipeline. Repair may include installation of an additional safety device of this type, or alternatively reinstating the safety device present in its original condition as shown in Fig.l by appropriate means, whatever is most appropriate from a cost poin-t of view.

In Fig.3 the- pressure in the pipeline is the customary some 70 -100 bar, the diameter of the pipeline being some 50-100 cm. The pigg 10 in this case will be compose of a preferably spherical pressure vessel 6 ¹ provided 5 with a pyrotechnical device 4, connected on its other side with an inflatable bag 5' , surrounded by a contin¬ uous reinforced fabric 2' . The diameter of this assembly should be sufficiently smaller than the inner diameter of the pipeline to allow its passage, but large enough

10 to be carried along by the gas flow. The pressure in the inflatable bag 5' will usually be the same as in the main pipeline as the bag will be installed with atmospheric pressure, and will be compressed by the gas pressure in the pipeline. Optionally the continuous

15 reinforced fabric may be embedded in the wall of the inflatable bag 5' , but the continuous reinforced fabric is preferably surrounding the inflatable bag 5' as otherwise friction between the pipeline and the material of the wall of the inflatable bag might cause undue wear

20 of the latter. The pressure vessel 6' may have another shape than spherical, and contains a high pressure suitable inert gas, the pressure being some 200 bar, or higher if required.

25 In Fig.4 the pyrotechnical device 4 has been broken in the same way as described for Fig.2, but here a wire connection is hardly feasible. The inflatable bag 5' will thus be inflated until its surrounding reinforced fabric fits tightly against the inner wall of the pipe-

30 line, this providing the desired result, i.e. closing of the pipeline, once the pigg 10 has reached a suitable position. Optionally the bag may be provided with an aααitional pyrotechrical device 4, having a different triggering wavelength, in order to release the pressure

V:. froτ. the Dag after appropriate repair of the pipeline, tn u ^; cllowing resumption of free flow through saiα peline.

Having thus described the functioning of a safety devic according to the invention it will be obvious that the device as shown in the Figures may be varied or modifie without departing from the concept of the invention. A safety device according to the present invention offers a number of advantages such as for example te following It is reliable in operation as it has no moving parts. It does not require foreign energy as it is using its own "canned" energy in the pressure vessel. Remote control allows safe operation of the pyrotechnical device under all circumstances. The safety device will provide closing of the pipeline within seconds after activating the pyrotechnical device, which latter may be a rupture plate or optionally a cone tightly fitting in a conical aperture and with its larger diameter faci the pressure vessel; thus the cone will be kept in position by the high pressure in the pressure chamber until the cone is removed by triggering the explosion, the explosion can be caused by any suitable explosive mixture, positioned against or in the vicinity of the pyrotechnical device. Furthermore the safety device according to the invention is maintenance free. In open position it does not provide obstruction to normal gas flow. The safety device is also fire safe and easy to install in any position. It permits quick action in order to restrict the quantity of gas escaping to the surrounding atmosphere or into the sea and will limit dangers in case of fire or explosion.

it will be obvious that the safety devices described above, if desired and applicable, be used for all sorts of pipelines, such as exploration and exploitation pipe for natural gas and/or oil, or also for pipelines conve ing oil or oil/gas mixtures between off-shore productio platforms or between such platforms and landing sites o any such pipelines on land. This also holds for applica tions in other sectors of industry such as chemical in- - dustry, nuclear energy'and the like.