GB2201623A

GB2201623A - Improvements in and relating to the purging of pipework

Info

Publication number: GB2201623A
Application number: GB08804455A
Authority: GB
Inventors: Anthony Francis Silmon; Joseph Anthony Michael Silmon
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-02-25
Filing date: 1988-02-25
Publication date: 1988-09-07
Anticipated expiration: 2008-02-25
Also published as: GB2201623B; GB8704457D0; GB8804455D0

Abstract

A method and apparatus for the puring of pipework, particularly during tungston inert gas welding comprises locating a first dam member (1) within the first pipe end (21), locating a second dam member (2) within a second pipe end (22). The two pipe ends are brought into abuttment, then purging gas is introduced into the space between the two dam members and allowed to leak controlably from said space during formation of the weld between the two pipe ends. The apparatus may extend far enough to allow two joints of an intermediate pipe section and a further dam member allows a side branch to be welded (Fig. 2 not shown). <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO THE PURGING OF PIPEWORK The present invention relates to an improved method and apparatus for the purging of pipework, particularly, though not exclusively, for the purging of pipework during tungsten inert gas (TIG) welding.

Conventional purging methods require the purging of a long length, typically 30 to 40 metres of pipework to allow a TIG weld repair to be carried out. This means that a large amount of purging gas, typically argon, is required, particularly with pipework of large diameter.

Conventional methods can also result in the collapse of the pipework under the influence of external forces such as hammering and the use of external clamps to align the pipe walls. Such collapse can occur during "tacking-up", or when the "weld root-run" is almost completed.

"Tacking-up" is the phrase used to describe the process of applying a number of small welds or "tacks" to the joint to be welded to hold the two pieces of pipe together without the use of a clamp or jig.

Typically, four such tacks would be spaced equidistantly around the circumference of the pipes.

"Weld root-run" is a phrase used to describe the process of applying the first section of weld to the joint which fuses together the internal edges of the material of the pipe. With pipes of thin material, one such weld may be sufficient to weld the joint satisfactorily, but with pipes of thick material more than one weld run is usually required.

Should the pi#ework collapse at the end of the "weld root-run", the weld has to be removed and the whole process repeated which is very time consuming.

It is therefore the aim of the present invention to provide apparatus for the purging of pipework which overcomes the above-mentioned disadvantages.

According to the first aspect of the present invention there is provided a method of purging pipework during the further treatment of said pipework, the method comprising locating within said pipework at least two dam members such that a space is defined therebetween, introducing purging gas into said space and allowing controlled leakage from said space during said further treatment.

The further treatment may comprise the formation of single joint, preferably by TIG welding, between two pipe ends, and in this case the method comprises locating the first of said dam members within the first pipe end and locating the second of said two dam members within a second pipe end, and bringing said two pipe ends into abuttment to define the space between the two dam members.

It should be appreciated that it is not necessary to install the apparatus within the pipes prior to bringing the pipe ends into abuttment - the apparatus can be installed either before or after "tacking-up" whichever is preferred or convenient, by removal of a valve or two from the pipeline.

It may also be necessary to connect an intermediate pipe length between first and second pipe ends, and in this case the further treatment comprises the formation of two joints, the first joint between the first pipe end and the first end of the intermediate pipe length, and a second joint between the second pipe end and the second end of the intermediate pipe length, the method comprising locating the first of said two dam members in said first pipe end, and locating the second of said two dam members in the second pipe end, and defining the space between the two dam members by bringing said first and second pipe ends into abuttment with a respective end of said intermediate pipe length.

It is also required from time to time to connect a lateral pipe to a main pipeline by the use of an intermediate pipe length in the form of a tee piece having a third end for connection to an end of the lateral pipe, and in this case the further treatment comprises the formation of three joints, a first joint between said first pipe end and the first end of the intermediate pipe length, a second joint between said second pipe end and the second end of the intermediate pipe length, and a third joint between said third end of said intermediate pipe length and an end of said lateral pipe, the method further including locating at least one further dam member in said lateral pipe end and defining said space between the dam members by bringing said first pipe end, said second pipe end and said lateral pipe end into abuttment with a respective end of said intermediate pipe length.

It is preferred that the gas is passed through a filter prior to its introduction into the space between the dam members, the purpose of the filter being to allow the purging gas to be injected into the space between the dam members at high volume per minute whilst avoiding the blast effect that would accompany directing injection of gas through a normal hose end.

According to a second aspect of the present invention there is provided apparatus for purging pipework during further treatment of said pipework, the apparatus comprising at least two dam members adapted for location within said pipework such that a space is defined therebetween, feed means for introducing purging gas into said space, and venting means for allowing controlled leakage from said space during said further treatment.

Conveniently, the two dam members are connected together by an elongate member of sufficient flexibility to allow the apparatus to be drawn through a bend in the pipework of up to 900.

In a preferred form, the elongate member is a hollow tube and has one end adapted for connection to a supply of purging gas and the other end blanked off, and a number of apertures are provided in the hollow tube between said ft and second ends through which the purging gas is introduced into the space between the two dam members.

Conveniently, each of said two dam members is secured to an associated dam mounting. One of the dam mountings is fixedly secured on the elongate member, whereas the other of the two dam mountings is slidably mounted on the elongate member for sliding movement along the longitudinal axis of the elongate member. The purpose of the sliding mounting is to allow the pipe fitter to move the pipe ends into abuttment during the final setting-up operations.

Preferably, each of the dam members has a central hole therein for accommodating the dam mounting, and the dam member is secured to the dam mounting by means of a locking nut which engages with a threaded portion of the dam mounting and can be turned to press the dam against a flange on the dam mounting.

Conveniently, at least one of the dam mountings includes attachment means such as a hook or the like to allow a rope to be attached to the apparatus to draw it into and through the pipe and to remove it from the pipe when the welding is completed.

For use in a method of joining a lateral pipe to a main pipeline by means of a tee piece, the apparatus also includes a further pair of dam members for locating within the lateral pipe end, both of said further dam members being fixedly mounted on an elongate hollow member which is open at both ends to act as venting means for the purging gas introduced between the pair of dam members located in the main pipeline and one of the dam members in the lateral pipe end.

The invention also resides in said further pair of dam members per se as well as in combination with the other pair of dam members.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a partially cut away view of the apparatus according to the invention installed within a main pipe; Figure 2 is a partially cut away view of the apparatus according to the invention installed within a main pipe and further apparatus also in accordance with the invention installed within a lateral pipe connection to the main pipe via a tee piece; Figure 3 shows the flexibility of the tube allowing the apparatus to be drawn through a 900 bend in the pipe; Figure 4 is a more detailed side view of the mountings for the dam members; Figure 4a is a cross-section through the fixed mounting of Figure 4; Figure 5 is an end view of a dam member; Figure 5a is a side view of the dam member;; Figure 6 is an end view of the gas filter in place on fixed mounting; Figure 7 is a side view of the further device shown in Figure 2; Figure 8 is a perspective view of a modified apparatus for use with very large diameter pipework.

Referring to the drawings, apparatus in accordance with the present invention comprises two dam members 1, 2 each in the form of a disc ld of high heat resistant rubber with two plastic plates la, lb moulded onto each side.

Each dam member has a central hole lc for accommodating the body portion 3, 4 of an associated dam mounting 5, 6. One of the dam mountings 5 is rigidly fixed on an elongate member in the form of a flexible hollow tube 7 passing through the centre of the mounting, whereas the other dam mounting 6 is slidably mounted on the tube. One end 7a of the tube has a threaded portion to receive a standard argon hose pipe, and the other end 7b is blanked off and includes a stop 8 to prevent the sliding mounting from sliding off the tube.

The two dam members 1, 2 are secured against flanges 9, 10 on the dam mountings, by means of locking nuts 11, 12 which may equally be of the wing nut type since it is sufficient to secure the dam members 1, 2 hand tight against flanges 9, 10.

The fixed mounting 5 has a connection 13 for an electric lightbulb 14 and a bayonet connection 15 for 110 volt electrical cable. The fixed mounting 5 may also include a battery pack (not shown).

In use, the two dam members 1, 2 are introduced into a pipe 20 with dam member 1 in the first pipe end 21 and dam member 2 within a second pipe end 22 by means of a rope as later described. This may be done prior to "tacking-up" or after "tacking-up", but prior to the "weld root-run Purging gas such as argon is then introduced into the hollow tube 7 through the threaded hose connection 7a. It cannot escape from the blanked offend of the tube and it is therefore forced out through slots or holes 25 drilled into the tube in the region where it passes through the fixed mounting (see figure 4a#.

The purging gas is forced to pass through a fine gauze filter 26 located on the fixed mounting, and passes into the space 27 defined within the pipe between the two dam members 1, 2.

Initially, before the weld is formed in the joint between pipe ends 21, 22, the purging gas will tend to escape through the gap between the two pipe ends, but as the weld progresses it will be forced to escape through small vent holes 30 provided in each dam member 1, 2.

Each dam mounting may have provided thereon a washer 31 with a hook 32 ' h tc ~ which #pe an be attached to introduce the apparatus into the pipework and to pull the apparatus from the pipework after welding is completed.

The constant flow of purging gas past the area being welded has a cooling effect, and enables the dam members and the central tube to be made of flexible materials which are capable of withstanding the temperatues which tend to build up during welding.

Figure 3 shows the flexibility of the tube being utilised to draw the apparatus through a 900 bend in the pipe.

Figure 2 shows the use of the apparatus in the welding of a lateral pipe 33 into a main pipe via a tee piece 34.

This requires the welding of three joints, a first joint 35 between a first pipe end 21 and a first end of the tee piece, a second joint 36 between the second pipe end 22 and the second end of the tee piece, and a third joint 37 between a third end of the tee piece and the lateral pipe end.

The apparatus shown in Figure 1 is located in the pipeline, and a modified piece of apparatus also comprising two dam members 40, 41 both fixedly mounted on the shorter, narrower hollow tube 42 is located within the end of the lateral pipe. Each dam member 40, 41 is mounted on associated dam mounting 45, 46 in a similar manner to that described above.

However, the hollow tube does not have a connection for a gas supply and is open at both ends to allow purging gas to be vented through the tube. In use, purging gas is introduced via end 7b of tube 7 in the main pipe, initially escaping through joints 35, 36 and 37 and eventually being forced to leak through vent holes 30 in the dam members 1, 2 and also through the vent hole 42. This ensures a cooling flow of purging gas passed each joint being welded.

This modified apparatus can be removed from the pipework by means of a short cable 50 attached to dam mounting 45, the other end being attached to tube 7, whereby the two pairs of dam members can be removed by the use of one rope.

Figure 8 shows a further modification to the apparatus of Figure 1, for use with very large diameter pipework, in which, in addition to the central tube 7, three smaller solid flexible rods 52 are attached between the two dam members 1, 2 to brace them apart, tnts ensuring that the system is safe from buckling or collapsing. Typically, the three rods 52 would be equally spaced around the dam members about 3 inches from the edge of the dam members.

The apparatus in accordance with the present invention enables a much smaller volume of purging gas to be required, typically sufficient to purge 0.5 metres. Also, the dam members will not collapse during the welding operation which has hitherto been the major problem with conventional methods.

Claims

1. A method of puring pipework during further treatment of the pipework, the method comprising locating within said pipework at least two dam members such that a space is defined therebetween, introducing purging gas into said space and allowing control leakage from said space during said further treatment.

2. A method according to Claim 1 in which said further treatment comprises the formation of a joint between two pipe ends, the method comprising locating a first of said two dam members in a first pipe end and locating a second of said two dam members in a second pipe end, said space being defined by bringing said two pipe ends into abuttment.

3. A method according to Claim 1 in which said further treatment comprises the formation of two joints, a first joint between a first pipe end and a first end of an intermediate pipe length, and a second joint between a second pipe end and a second end of said intermediate pipe length, the method comprising locating the first of said two dam members in said first pipe end and locating the second of said dam members in said second pipe end, said space being defined by bringing said first and second pipe ends into abuttment with a respective end of said intermediate pipe length.

4. A method according to Claim 3 in which the intermediate pipe length includes a third end for connection to a lateral pipe end, and said further treatment comprises the formation of three joints, a first joint between said first pipe end and said first end of said intermediate pipe length, a second joint between said second pipe end and said second end of said intermediate pipe length, and a third joint between said third end of said intermediate pipe length and said lateral pipe end, the method further including locating at least one Further dam member in said lateral pipe end, said space being defined by bringing said first pipe end, said second pipe end and said lateral pipe end into abuttment with a respective end of said intermediate pipe length.

5. A method according to any of the preceding claims in which the purging gas is passed through a filter prior to its introduction into said space.

6. Apparatus for purging pipework during further treatment of the pipework, the apparatus comprising at least two dam members adapted for location within said pipework such that a space is defined therebetween, feed means for introducing purging gas into said space, and venting means for allowing control leakage from said space during said further treatment.

7. Apparatus according to Claim 6 in which said at least two dam members are connected together by an elongate member of sufficient flexibility to allow the apparatus to be drawn through a bend in the pipework of up to 900.

8. Apparatus according to Claim 7 in which the elongate member is hollow and has one end adapted for connection to a supply of purging gas, the other end being blanked off and a number of apertures being provided in the elongate member between said first and second ends through which, in use, the purging gas is introduced into said space.

9. Apparatus according to Claim 8 in which each of said at least two dam members is secured to an associated dam mounting.

10. Apparatus according to Claim 9 in which one of said dam mountings is fixedly mounted on said elongate member and the other of said dam mountings is slidably mounted on said elongate member for sliding movement along the longitudinal axis of the elongate member.

11. Apparatus according to Claim 9 or Claim 10 in which one of the dam mountings has associated therewith a filter through which, in use, the purging gas passes.

12. Apparatus according to any of Claims 9 to 11, in which either or both of said dam mountings includes attachment means by which a rope or the like may be attached to the apparatus.

13. Apparatus according to any of Claims 6 to 12 and including a further pair of dam members for location within an end of a lateral pipe to be connected to an intermediate pipe length located between said first and second pipe ends, said space being defined between said first pair of dam members and one of said further pair of dam members.

14. A method according to Claim 1 and substantially as herein described with reference to the accompanying drawings.

15. Apparatus according to Claim 6 and substantially as herein described with reference to the accompanying drawings.