FR2461879A1 - METHOD OF INTERVENTION ON DIGITAL GAS DRIVE BY MOMENTANEOUS PARTIAL WATER SUPPLY OF SAID DRIVING - Google Patents

Abstract

THE INVENTION MAKES IT POSSIBLE TO ENSURE THE SAME SAFETY AS DURING INTERVENTIONS ON DUCTS CONDUCTING A LIQUID. THE DISTANCE METER SHUTTER 6 IS CONDUCTED BY PRESSURE OF THE GAS AT 22 UP TO A GIVEN DISTANCE FROM THE PLACE OF INTERVENTION 4 OR IT BLOCKS. THE SIMILAR SHUTTER 24 IS CONDUCTED BY PRESSURE IN 25 BY PROMOTING THE CONTROLLED WATERING OF THE TRUNCON 26. THE DAMAGED PART IS REPLACED AND THE DAMAGED PART IS DISCHARGED BY A NEW APPLICATION OF PRESSURE IN 22 THE SET 6 TO 24 WITH WATER, GAS AND ESPECIALLY WATER. THE INVENTION APPLIES PARTICULARLY TO OIL GAS EFFLUENT PIPES.

Description

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  The invention relates to a method of intervention on

  gas pipe immersed by impounding a water supply

  of that conduct and in particular where the intervention

  requires the replacement of a section of the pipe.

  We already know how to carry out such interventions when

  submerged pipelines channel liquid products.

  However, there is no method to perform

  an underwater intervention on a submerged can-

  reading a gas, the only known solution being to fill it

  of water so that it can safely proceed to

  desired underwater However, such an operation is long and costly since the restoration of the gas line requires, after the intervention, the evacuation of water from all the pipe and its drying along its entire length that can

  to reach several hundred kilometers.

  The object of the invention is a method of intervention on

  gas pipe immersed by partial impoundment of a

  said pipe by means of shutters, according to which a first automatic shutter is moved,

  one end of the pipe to a distance

  determined where the intervention is desired, the closure

  stuck in this position and in a sealed manner against

  the wall of the pipe, a second shutter with

  automatically engaging the other end of the a5 pipe by increasing and maintaining the internal pressure of the portion of the pipe between the second end and said

  shutter at a pressure greater than the pressure hysdrosta-

  at the place of intervention, an opening opening is

  given in the pipe at the place in question, we continue to ensure the displacement of the second shutter while maintaining

  said pushing pressure until the blocking of said second ob-

  at a predetermined distance from the place of intervention so that the section of pipe between the

  two tripping shutters are filled with water.

  It is then possible to safely execute all

  intervention, for example the establishment of a

  of the section of pipe, its debononnage, the cut of the damaged section, the preparation of an end brushing outside and inside, thin section, descent of the section of

  connection and connection of the new section.

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  It is therefore sufficient after the intervention to flush the water from the only section considered and for this purpose to hunt by simply pressing the shutters originally blocked and between which

  is the water used to ensure the pressure balance.

  Another object of the invention is to simultaneously perform any drying operation of the tube for a new commissioning of the gas line by doubling the first shutter automatically triggered by a single shutter and filling the gap between the two shutters of a product such as methanol for example intended to dry

wastewater by absorption.

  Another object of the invention is to carry out simultaneously any other operation of reinstatement of the pipe, for example by dissolving fat which may

  cover the inner wall with additional obturations

  between which are discharged all solvents

  properties -the entire shutter train and processing products being forced out to the end

of driving.

  Thus, the method has the advantage of offering the same safety during operation operations performed on liquid lines while drowning only a small amount of water.

  section of driving on the other hand to be of equivalent duration

  to that of interventions carried out on canal

  L5 sation of liquid while allowing a cleaning of the whole

lity of driving.

  Other features of the invention will appear in

  course of the following description made with reference to the drawings

  annexed examples which represent, by way of example, a method of

process.

  In the drawings, FIG. 1 is a general diagrammatic representation of a submerged pipe resting on a seabed, the figure showing the state of the pipe at

  place of intervention after the establishment of the first obtura-

  and in the approach phase of the second shutter, Figure 3 the representation of the portion of the pipe before stopping the second shutter, Figure 4 the schematic representation of a shutter with automatic release and,

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  FIG. 5 the representation of the state of the line after

  intervention during the recovery phase of the

gas.

  In order to facilitate the presentation of the general method of submarine intervention by momentary partial impoundment of a submerged pipe which does not channel liquid, it has been assumed that pipe 1 FIG. 1 was a gas pipe connecting a plate 2 marine platform where natural gas from an underwater borehole is channeled into the pipeline. This pipe is maintained on the seabed 3 in any way, and to counterbalance its buoyancy is covered with a concrete which for the sake of clarity of the drawing has not been shown. We have

  indicated by arrow 4 the place where an intervention was

  that the line present a dangerous deformation in this area or that the presence of a

leak, or for any other reason.

  For the sake of clarity, it will be assumed that the hydro-

  static instead of 4 is of the order of 10 bars and that the distance

  this separating the damaged place from the pipe of the platform

  form 2 is 100 km and that separating it from the reservoir of

  storage 5 at the other end of the pipe is 50 km.

  The first phase of the process consists of introducing the

  platform 2 at least one self-triggering shutter 6

  by built-in distance counter and capable of ob-

  pipe 1 by withstanding pressures of the order of

  bars for example in the case considered.

  Line 1 before, after repair, be ready to

  gas, which must be dried before reuse,

  complete the introduction of the shutter 6 by a certain volume

  me 7 of methanol trapped between the shutter with

  automatically 6 and a single shutter 8 insulating the metha-

  production gas that is then used to displace

  the whole to the place 4 o a leak for example has been de-

  tectée. The shutter 6 shown schematically in FIG.

  be of counting wheel type 9. Each wheel 9,

  designed to roll without slipping on the inner wall of the con

  1, is mounted on an articulated arm 10 of the support frame 11

  both sealing cups 12 and 13 and an inflatable sleeve 14. The cups 12 and 13 sealing

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  with the wall of the pipe while moving the shutter and regardless of the direction of travel. The sleeve 14, normally in the non-inflated position 15, is applied to the inner wall of the pipe 1 as soon as the reserve of gas under pressure contained in the tank 16 is

  released, for example as a result of the explosion of

  17 and 18. For this purpose the loads 17 and 18 are

  connected by the control wire 19 to the starting device 20.

  This is triggered by the odometer 21 when

  that the number recorded by the counter reaches a predetermined value. The means of the control of the counter 21 by means of the rollers 9, as well as the display means of

  the predetermined value of the distance of travel or

  triggering of the priming device 19 which can be any

  Although they are not the subject of the invention, these means have not been shown in detail. It's obvious that

  the wheel 9 can transmit any mechanical or electrical signal

  meter 21 and that the latter may, depending on its nature,

  snap directly by means of a spring control for example the movement of a finger normally locked by

  the display wheels of the meter, a system of notches

  these wheels and corresponding to the trigger value

  representing the displayed distance leading to the release of

  finger as soon as these notches are aligned. This trigger

  obviously can also be obtained by comparing the displayed value contained in an electromechanical counter

  or electronic with the value displayed on a means of communication

  electromechanical or electronic parison. It is then convenient

  to use multiple casters such as 9 to avoid

  any loss of control pulse and trigger the

firing rate 20.

  Having assumed in the example under consideration that the place of inter-

  4 is located 100 km from platform 2 and 50 km from station 5, counter 21 is then set to train

  triggering the priming device 19 as soon as it displays

the value of 99,900 m.

  The simple shutter 8 preferably includes means for

  sealing similar to the eggs 12 and 13 of the shutter 6

  to ensure watertightness regardless of the direction of chimney-

in driving.

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  When the shutter 6 reaches a hundred meters from the place of intervention 4 the counter 21 triggers the priming device 19 exploding the hollow charges 17 and 18 causing the release of the reserve 16 of pressure gas plating the cylindrical sleeve 14 of the shutter

6 against the wall of the pipe 1.

  Blocking the shutter 6 in the pipe causes an increase in pressure in the portion 22 of the pipe

  between the platform 2 distributing gas and the ob-

  8. The control of the pressure at the platform 2 makes it possible to detect the stop of the shutter 6. It is then possible to proceed to the control of the position of this shutter which one

  may equip any transmitting beacon 23 with any appropriate signal

  requested to be captured using any known device known

  worn by submarine. Although the increase in internal pressure at Part 22 of Line 1 could reach

  bars without moving the shutter, we bring the pressure

  the value of the hydrostatic pressure of the place of inter-

  4, that is to say in the example chosen at 10 bar.

  O At the station 5 is introduced a shutter 24 of the same type as the shutter 6 that is moved by pressure after having

  set its counter to trigger the pressurization of

  cage when the counter reaches the value 49.900 m. As soon as the pressure necessary to advance the shutter 24 in the part of the pipe 25 situated between the shutter 24 and the station 5 reaches a predetermined value, for example 20 bar, the evacuation of the gas contained in the part of the pipe 1 adjacent to the place of intervention 4 by making a hole of predetermined size 26 Figure 3 at the damaged location 4 of the pipe. For this purpose, a suitable pyrotechnic charge can be deposited by means of a submarine on line 1. After explosion, the gas trapped between shutters 6 and 24 at a pressure greater than the hydrostatic pressure escapes the orifice, so that

  it is possible to continue moving the shutter 24 to almost

  constant pressure in part 25 of the pipe. When the

  turateur 24 reaches the limit of the distance assigned to him his meter triggers the swelling of his cuff

  blocking plate against the wall of the pipe.

  The gas pressure between the shutters 24 and 6 being

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  then that of the hydrostatic pressure, the portion 26 'of the pipe between the shutters 24 and 6 is filled with water. As in the case of the blocking of the shutter 6, it is possible to check the position of the shutter 24 by means of signals emitted by a beacon placed in the shutter or even

by this one.

  It becomes possible to proceed to any intervention

  desired, and in particular to replace a section of the

  drowned 26 'of driving by a new section 27 figure

  5. Such an intervention can be performed safely.

  Part 26 can be raised by means of all

  firing, debonding and cutting the damaged, prepa-

  1 end of the pipe after removal of the damaged section for the weld connection of the new

  27 and carry out the necessary brushing operations

  outer and inner geometry and thin section of the end 29, then to the establishment of a closure cap 28 for the

  welding connection operations along line 32.

  It is unnecessary to further describe these known operations.

  The same procedure is carried out for the other end 30 which is completed

  by the introduction of the cap 31 in order to achieve the conne-

  xion of the new section 27 by welding along the line 33.

  This leads to a pipe comprising a portion 22 containing the natural gas to be channeled, a single shutter 8, and a self-closing shutter 6 both serving as partitions to a certain volume of methanol 7 for drying the pipe 1 in the course of the evacuation operation of the seawater introduced and remaining confined on the one hand between the plugs 6 and 28, on the other hand between the plugs 24 and 31. The zone between the plugs 28 and 31 is filled with dive gas used during the connection of the new section 27, and the zone 25 being filled with the gas having

  served at the thrust of the shutter 24.

  In order to drive the assembly bordered by the shutters 8 and 24 without having to exert strong thrusts, one chooses to

  Preferably, the sleeves 15 are not heat-resistant.

  continuous prolonged, even of rather short duration. It is therefore sufficient to increase the gas pressure of the portion 22 until one obtains the displacement of the shutter 6, the sleeve 15 heats up gradually and disintegrates. The

246 1879

  shutter cuff 24 disintegrating likewise, the pressure

  Eion of the thrust gas at 22 can be reduced. The set between the shutter 24 and the shutter 8 moves

  to station 5 where all the elements are collected.

  During this displacement the methanol dissolves the residual water so that after recovery at station 5, the pipe is ready to channel again the gas coming from the

platform 2.

  If the gas is loaded with fatty products adhering to the wall of the pipe 1, it is possible to precede the shutter 6 by an auxiliary shutter 34 similar to the shutter 8,

  the space between the shutter 6 and the shutter

  area 34 being filled with a suitable solvent 35.

  Although only one example of implementation of the method which is the subject of the invention has been described, it is clear that the partial watering can be used for operations other than those described and that it can be applied

  especially during non-flooded pipe laying tests.

  In addition, many detailed modifications can be made to the various operations, without departing from

  of the general principle of the process described, these amendments do not

  both due to the constraints encountered by the use

means available.

Claims (2)

CLAIMS A method of intervention on a gas-immersed line by partial impingement of a portion of said pipe by means of shutters, characterized in that a first shutter, with automatic release, is moved by one of the ends of the pipe to a predetermined distance from the place where the intervention is desired, the shutter being locked in this position and sealingly against the wall of the pipe, in that one moves a second shutter with automatic release from the other end of the pipe by increasing and maintaining the internal pressure of the portion of the pipe between the second end and the said shutter at a pressure greater than the hydrostatic pressure at the place of intervention, in what is practiced a given aperture opening in the pipe instead cons-i-derated and in that one continues to ensure the displacement of the second shutter while maintaining said pr thrust pressure until the blocking of said second shutter at a predetermined distance from the place of intervention.   20) Process as claimed in 1 according to which blocking   the first shutter so that this blocking resists a pressure   sion greater than that of the maximum pressure exerted on the second shutter during its movement towards the place of intervention.   ) A process as claimed in claim 1 wherein   that stopping the movements of the first-and second shutter   by automatic control of the distances of course.   ) A method as claimed in any one of   Claims 1 to 3 according to which the stopping of said shutters   automatic release is achieved by the self   sudden pressure on the side surfaces   shutters against the wall of the pipe.   A method as claimed in claim 4 wherein the triggering   The pressure is measured by counting the distance traveled and by blowing up a charge triggered at the equal of a pre-displayed distance and the distance of the distance. shutter course.   ) A method as claimed in any one of   Claims 1 to 5 according to which the procedure is   desired after verifying the location of said shutters by means of transmitting beacon signals located in said   shutters and a signal sensor aboard a submarine.   ) A method as claimed in any one of   claims 1 to 6, according to which, where   vention consists in replacing a section of the line at the place considered, a blanking plug at the ends of the pipe   obtained by cutting the section to be replaced.   ) A method as claimed in any one of   Claims 1 to 7 according to which the shutters are unlocked   after the desired intervention by increasing the pressure of a   driving part between one end and the closure   correspondent near the place of intervention until   partial truction of the locking means of the shutters with   automatic closing and the pressure is reduced to a   sufficient pressure to bring to the other end of the pipe shutters and plugs possibly introduced during the intervention, comprising between them a gas intervention, sea water being trapped between said plugs and the shutter releases.   90) A method as claimed in 8 wherein is added to the automatically triggered shutter introduced from the station or the gas distribution platform at least a single shutter and fills the space between these shutters of methanol before moving the whole by pressure.   ) A method as claimed in any one of   claims 8 and 9 according to which, in addition,   throttle trigger introduced to the station or platform   gas dispenser shape at least one simple shutter by filling the space between said shutters of a solvent.