GB2507302A

GB2507302A - Purge tee assembly

Info

Publication number: GB2507302A
Application number: GB1219183.9A
Authority: GB
Inventors: Derek John Muckle
Original assignee: Radius Systems Ltd
Current assignee: Radius Systems Ltd
Priority date: 2012-10-25
Filing date: 2012-10-25
Publication date: 2014-04-30
Anticipated expiration: 2032-10-25
Also published as: GB2507302B; GB201219183D0

Abstract

A purge tee assembly (10 figure 1) for purging a plastics mains pipeline comprises a saddle 18. It includes an electro-fusion element (24 figure 1). There is a hollow body 12 integral with the saddle and provided with an axial bore (26 figure 1) and an externally screw threaded end (30 figure 1) distal to the saddle. The threaded end receives a first screw cap (34 figure 1). A cutter (28 figure 1) is disposed within the bore and is advanceable and withdrawable to cut a hole in the mains pipe when the saddle is fitted thereto. There is a tubular spigot (22 figure 1) integral with the hollow body and having a spigot bore (22a figure 1) in fluid connection with the axial bore of the body. The spigot has an externally screw threaded distal outlet (22b figure 1) and a second screw cap (40 figure 1). The assembly further comprises a vent sleeve 50 having a first section 51, a second section 53 and means 55 for fixing the vent sleeve to the hollow body when the second screw cap is removed. The first section of the vent sleeve is locatable on the spigot with its longitudinal axis substantially parallel the spigot bore and the second section of the vent sleeve extending substantially parallel the axial bore of the hollow body

Description

Purge Tee Assembly This invention relates to a purge tee assembly! and more particularly to a purge tee assembly for use in the commissioning and decommissioning of mains gas pipes, particularly plastics pipes.

BACKGROUND

When commissioningldecommissioning a mains pipe, it is the aim of the engineer to prevent the mixing of air and natural gas. Presently, in the field, engineers make use of existing tapping assemblies to purge pipes. However this approach can lead to inconsistencies and may at times be unreliable or unsafe. Indeed, there do not seem to be any established procedures for purging a mains pipe, either of gas with fresh air when it is required to work on the pipe, or of air with gas when work is complete and the pipe is to be put into service again. One known procedure involves the cobbling together of a tapping tee on the mains pipe with a length of plastics pipe to which a vent pipe (usually of metal) is connected and supported in an upstanding position. When the arrangement is complete, the plastics pipe is squeezed with a pinch-off clamp to seal the end. When ready, the pipe is purged by opening the pinch clamp. Once the pipe is purged, the pinch clamp is closed again and the vent is removed leaving a free end of plastics pipe beyond the pinch clamp. This is then sealed by an end cap, usually electro-fused to the end and the clamp removed. However, this leaves a length of live, but useless, pipe in the trench and poses an unnecessary risk. Gas leaks are desirably avoided at all times, but releases to the atmosphere of small amounts of gas are not detrimental, provided no ignition source is near at hand. Because the existing method employs an electrofused end-cap seal as the final stage of the venting process, the pinch clamp must be 100% effective. There are two reasons for this. The first is purely in relation to the ignition danger presented by an external heat source employed during electrofusion of the end cap. The second is the possibility of gas pressure building up against the end cap before the electrofusion is complete, with the possibility of a leak through a pinch clamp also penetrating the electrofused region of the end cap.

It is an object of the present invention therefore, to provide engineers in the field with a safe, reliable and efficient means to purge mains pipes.

A tapping tee is a fitting that can be mounted on a pipeline. Typically, tapping tees comprise a body with a through bore, a saddle that contours the main pipe, and a spigot through which a branch pipe can be connected. The spigot has a spigot bore connecting the body bore to branch pipe. The saddle contains an electrofusion element (or other components incorporating an electrofusion element such as an electrofusion element mat), that is embedded in fusible polymer material to facilitate the bonding of the tapping tee to the mains pipe. Pipe assemblies provided with saddles and saddle-shaped electrofusion elements and mats are disclosed in US patents 4933037, 4806181, 5104468, 5601315, and 5348045, and in UK patent application GB2310264.

The entire disclosures of these patents are incorporated herein by reference for all purposes.

In some tapping tees an integral cutter is disposed in the body, and is arranged to be driven through the body of the fitting in order to cut a hole in the mains pipeline through the saddle after the saddle has been fixed on the mains pipe and after the branch line has been completed and fitted to the tapping tee spigot. Indeed, such an arrangement can be used with the mains pipe live, since the cutter with the coupon of pipe cut from the mains pipe forms a seal in the body until the cutter is withdrawn past the branch into the spigot. Thereupon, a winding tool, used to advance and withdraw the cutter (which is, in this event, threaded and engaged with a corresponding thread of the body bore) is removed and a cap fitted on the top of the body to seal the tapping tee. For this purpose, the outside of the tapping tee body near its opening is also threaded to receive the correspondingly threaded cap, which may be provided with an elastomeric seal to form a permanent seal. Any leakage past the cutter/coupon combination is small and non-consequential, soon stopped altogether by the mechanical attachment of the cap.

An improved purge tee assembly is described in our earlier patent GB2453569B in which a tubular spigot connected to the main hollow body of the assembly is in fluid connection with an externally screw-threaded distal outlet substantially parallel the axial bore of the hollow body. A plastics screw cap is screwable on the screw-threaded distal outlet.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect of the present invention there is provided a purge tee assembly for purging a plastics mains pipeline comprising: a saddle, provided with a saddle-shaped saddle electrofusion element; a hollow body, integral with the saddle, and provided with an axial bore and an externally screw threaded end distal to said saddle, said externally threaded end to receive a first screw cap; a cutter disposed within said axial bore and advanceable and withdrawable therein to cut a hole in the mains pipe when the saddle is fitted thereto; and a tubular spigot, integral with the hollow body, and having a spigot bore in fluid connection with the axial bore of the body, the spigot having an externally screw threaded distal outlet and a second screw cap, characterised in that the assembly further comprises a vent sleeve having a first section with a first longitudinal axis, a second section with a second longitudinal axis substantially perpendicular to the first longitudinal axis, and means for fixing the vent sleeve to said hollow body, whereby, when said second screw cap is removed, the first section of the vent sleeve is locatable on the spigot with the first longitudinal axis substantially parallel said spigot bore and the second section of the vent sleeve extending substantially parallel the axial bore of the hollow body.

Preferably the first section of the vent sleeve includes a channel for receipt therein of the hollow body of the purge tee assembly. The fixing means may be a retaining pin for retaining the hollow body within the channel or, alternatively, a screw cap retainer could be used or any other suitable fixing moans.

Preferably the second section of the vent sleeve is capable of supporting a conventional vent pipe or purge pipe. These are typically of substantial height and weight such that the spigot per so of a conventional purge too would not be able to support thorn. The assembly may include such a vent pipe for connection to the second section of the vent sleeve. To facilitate efficient and safe purging, said vent pipe preferably extends at least one metre vertically above said plastics pipeline when attached thereto. The vent pipe may be metallic, for example aluminium or steel.

0-rings, or other suitable seals may be provided on the body and/or the distal outlet to enhance the seal made by the first and second screw caps or other ancillary apparatus.

The vent sleeve may also seal against an 0-ring at the distal outlet.

The configuration of the bend in the vent sleeve, for example a swept bend, may be selected in order to optimise fluid flow.

Preferably, said cutter and said axial bore are screw threaded in a complementary fashion thus allowing controlled translation of said cutter within said bore. Said cutter preferably comprises a polygonal socket for engagement with a complementary tool.

Preferable complementary tools include a winding tool and a top loading clamp.

In one preferable embodiment, said saddle, body and spigot are integrally moulded.

Integrally moulded assemblies comprise one single air-tight component and thus avoid potential problems with leaking seals and joins.

In use, when a mains pipe is ready to be purged, the purge tee is fused to the mains pipe at an appropriately extreme end of mains pipe. Such a process is conventional and needs no further explanation here. The vent sleeve is slid over the spigot of the purge tee and fixed in place. The vent sleeve is suitably connected to a vent pipe, for example by screwing the vent pipe thereto. A winding tool is engaged with the cutter, which is then advanced to cut a hole in the wall of the mains pipe. The cutter and coupon between them still seal the axial bore. When the cutter is withdrawn past the spigot bore, gas, or air, in the mains pipe can escape. The purge tee can then allow the safe commissioning of the mains gas pipe from air to natural gas, or decommissioning from natural gas to air, by allowing fluid from the main pipeline to be safely vented when the cutter is removed.

When fully purged, the winding tool is re-advanced to re-engage the cutter with the hole in the mains pipe, thereby closing off the spigot bore and resealing the mains pipe (albeit temporarily and possibly even with some non-consequential leakage). The winding tool is then removed and so also is the vent sleeve and vent pipe, and caps are fitted on the threaded ends of both the axial bore and the distal outlet, permanently sealing the purge tee. The purge tee remains on the mains pipe and may serve on future occasions to purge the pipeline, because the cutter and coupon remain in place and can be employed again as temporary valve members. Moreover, the purge tee is now the minimum unnecessary' appendage of the mains pipe and represents less of a risk of accidental damage in the event of subsequent excavation in the vicinity of the pipeline.

Furthermore, the final seal of the arrangement is provided by the screw caps. There is no requirement therefore for any heat source. Consequently, there is no reason why a small leakage should be problematic. Firstly, screwing the cap shut makes a complete seal, which is not compromised by a small leak past the cutter and its coupon.

Secondly, since no heat is employed there is no danger of ignition. Preferably, the screw cap is also made from plastics material, whereby the risk of a spark hazard is non-existent.

According to a second aspect of the present invention, there is provided a method of purging fluid in a plastics pipeline, using a purge tee assembly as described in any of the preceding paragraphs, said method comprising the steps of: electro-fusing said purge tee assembly to said plastics pipeline; U. fitting said vent sleeve to the spigot; Hi. fitting a vent pipe to said vent sleeve; iv. translating said cutter down said axial bore and cutting a hole in said plastics pipeline; v. translating said cutter upward through said axial bore such that said spigot bore is in fluid connection with said plastics pipeline; vi. venting unwanted fluid from said plastics pipeline; vii. translating said cutter down said axial bore such that said cutter is disposed in said hole to temporarily, at least partially, close fluid connection between said pipeline and spigot bore; viii. removing said vent pipe and vent sleeve; and ix. sealing said purge tee assembly by screwing said first and second screw caps onto said externally threaded end of said hollow body and said distal outlet respectively.

Preferably, said plastics pipeline is scraped to remove nominally 0.2 to 0.4 mm of its surface prior to executing step i). Scraping removes surface dirt and oxide layers that may reduce the quality of the electrofusion weld. For the same reason, it is further preferable to maintain a high level of cleanliness at the worksite when electrofusing.

Preferably, said cutter is translated along said axial bore by rotation of said winding tool when engaged with said socket.

Preferably, said method further comprises the steps of testing the integrity of the purge tee assembly and its air-tightness prior to step ii). Seals may be tested by a variety of means including pressure testing. Such practice minimises the risk of potentially harmful fluids escaping from faulty seals of the assembly.

To ensure that said purge tee assembly is squarely fitted to said plastics pipeline and that said assembly does not move during electrofusion, said assembly is preferably secured to said plastics pipeline by a clamp tool during step i). Preferably, said clamp tool engages with said socket and applies a downward force to said purge tee assembly for the duration of step i). In this preferable arrangement, said clamp tool has a secure connection to said purge tee assembly and will be inclined to prevent undesirable lateral movement of the purge tee assembly during clamping, thus ensuring a better electrofusion weld.

Further features of the invention are defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are further described hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an exploded sectional side view of purge tee assembly in accordance with the present invention (excluding vent sleeve); Figure 2 is a perspective view of a purge tee assembly including a vent sleeve; Figure 3 is a top view of a vent sleeve; Figure 4 is a sectional side view of the purge tee assembly including vent sleeve in place on a service pipe; and Figure 5 is a sectional side view of the purge tee assembly after venting, with the vent sleeve removed and second screw cap in place.

DETAILED DESCRIPTION

Referring to Figure 1, the purge tee assembly 10 comprises an integrally moulded saddle 18, body 12 and spigot 22. The saddle 18 is provided with a saddle-shaped electrofusion element mat 24 (described further in GB2453569B), which is attached thereto by over-moulding, snap-fit, screws or other fastening means (not shown). The body 20 has an axially extended screw threaded bore 26, and a metal cutter 28 disposed within the bore. The cutter 28 has a screw threaded outer surface 29 that cooperates with the screw thread of the bore, and a circular cutting edge 31. The top of the body 20 has an 0-ring 32 and an external screw thread 30 to receive a first screw cap 34, whereby a tight seal of the open end of the axial bore 26 may be assured.

The spigot 22 is hollow and has a spigot bore 22a extending perpendicularly from the body 20 to an externally screw-threaded distal outlet 22b having an 0-ring 36 and a second screw-threaded end cap 40 operating in the same manner as the first screw cap 34 described above.

Figures 2 and 3 illustrate a vent sleeve 50 having a first section 51, a second section 53 and an intermediate bend 52 therebetween. The first section 51 has a first longitudinal axis Li and the second section 53 has a second longitudinal axis L2. The axes Li and L2 are preferably perpendicular to one another. The intermediate bend 52 is a formed bend (e.g. a swept bend to optimise flow).

The vent sleeve 50 includes a channel 54 for receipt of the body 12 and fixing means, for example a retaining pin 55 to hold the sleeve in place against the upstanding body 12. Alternatively, a screw cap retainer (not illustrated) could be used to hold the vent sleeve in place.

Engagement of the vent sleeve 50 with the body 12 avoids rotation of the sleeve about the first longitudinal axis Li which would cause undesirable movement of the second section 53 away from the vertical position.

The purging procedure is largely as described in GB2453569B and illustrated schematically in Figures 3a to d thereof. In the first step, the purge tee assembly 10 is assembled with the components shown in Figure 1 i.e. with the second end cap 40 in place on the distal outlet 22b of the spigot. The purge tee assembly is to be electrofused to the mains pipe 60. Before this step can be implemented, the immediate environment around the pipe and fitting to be jointed, must be clean and dry. It is generally recommended that electrofusion takes place under a welding shelter to assist in preventing airborne dust or rain from contaminating the pipe surface once prepared.

The pipe is then scraped to remove nominally 0.2 to 0.4 mm of its surface so that surface dirt and oxide layers do not impede the electrofusion process.

When electrofusing the purge tee assembly 10 to the mains pipe 60, the metal cutter 28 is disposed at the top of the bore 26 and is flush with the top of the body 12. The metal cutter 28 comprises a hexagonal socket (not shown) to receive a tee bar (not shown) which winds the metal cutter 28 up and down within the threaded bore 26. To ensure that the purge tee assembly 10 does not move during electrofusion, a top loading clamp tool is inserted into the hex socket in the metal cutter 28, which then facilitates the downward application of an appropriate load onto the purge tee assembly 10.

Once the electrofusion element has been energised and the melted fusible polymer allowed to cool and set, the integrity of the weld is tested by removing one of the end caps 34, 40 and performing a pressure test.

With the purge tee assembly 10 securely welded to the desired location, the end cap 40 is removed and the vent sleeve 50 is slid over the spigot 22, secured in place by the retaining pin 55. A conventional vent pipe (not illustrated) is fitted to the vent sleeve 50.

The vent pipe can be connected to the vent sleeve by a variety of means, for example by screw thread. It is of note that the vent pipe is of substantial (perhaps 2 -2.5m) height and the retention of the vent sleeve against the body 12 assists in providing support for the vent pipe. Additional support for the vent pipe may also be provided to avoid undesirable loads being imposed on the purge tee assembly 10. In addition to (or instead of) vent pipe, other ancillary components such as pressure measuring instruments, can be connected to the second section 53 of the vent sleeve 50.

A coupon 60a is then cut out of the mains pipe 60 using the metal cutter 28. Cutting of the mains pipe 60 is done by first removing the first screw cap 34, inserting the bottom end of the tee bar into the complementary hex socket of the metal cutter 28, and then rotating the tee bar clockwise such that the metal cutter travels downward within the bore 26 and cuts into the mains pipe 60. The coupon 60a cut from the mains pipe 50 remains lodged within the cutter 28 thereafter, leaving a circular hole 60b in the crown of the mains pipe 60.

Once the vent sleeve 50 and vent pipe are securely fitted, and integrity tested, the purging process can take place. Thus, after cutting hole 60a in the pipe 60, the cutter 28 is returned to the top of the bore 26 (to the position illustrated in Figure 4) using the tee bar and the first cap 34 replaced. This opens connection between pipe 60 and the vent sleeve 50, enabling venting of the contents of the pipe 60. In this respect, cutter 28 and its coupon 6Db act as a valve. When purging is complete, the cutter 28 is wound down once again using the tee bar, into the hole 60b it created previously, effectively acting as a plug (Figure 5). The gas source is isolated at this point, thus allowing any ancillary components such as the vent sleeve 50 and vent pipe, to be safely removed from the spigot 22. The tee bar is then disconnected from the hex socket of the cutter 28 and withdrawn from the bore 26, leaving the cutter 28 disposed in the hole 60b.

Finally, both screw caps 34, 40 are secured over their respective external screw threads 30,38, permanently sealing the assembly.

The procedure described above can thus be used to purge air before the introduction of natural gas when commissioning a mains pipe, or similarly, to purge natural gas before the introduction of air when decommissioning a mains pipe.

Throughout the description and claims of this specification, the words "comprise" and "contain' and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination! except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A purge tee assembly for purging a plastics mains pipeline comprising: a saddle, provided with a saddle-shaped saddle electrofusion element; a hollow body, integral with the saddle, and provided with an axial bore and an externally screw threaded end distal to said saddle, said externally threaded end to receive a first screw cap; a cutter disposed within said axial bore and advanceable and withdrawable therein to cut a hole in the mains pipe when the saddle is fitted thereto; and a tubular spigot, integral with the hollow body, and having a spigot bore in fluid connection with the axial bore of the body, the spigot having an externally screw threaded distal outlet and a second screw cap, characterised in that the assembly further comprises a vent sleeve having a first section with a first longitudinal axis, a second section with a second longitudinal axis substantially perpendicular to the first longitudinal axis, and means for fixing the vent sleeve to said hollow body, whereby, when said second screw cap is removed, the first section of the vent sleeve is locatable on the spigot with the first longitudinal axis substantially parallel said spigot bore and the second section of the vent sleeve extending substantially parallel the axial bore of the hollow body.
2. A purge tee assembly as claimed in claim 1, wherein said first section of the vent sleeve includes a channel for receipt therein of the hollow body.
3. A purge tee assembly as claimed in claim 2 wherein said fixing means comprises a retaining pin for retaining the hollow body within said channel.
4. A purge tee assembly as claimed in claim 2 wherein said fixing means comprises a screw cap retainer for retaining the hollow body within said channel.
5. A purge tee assembly as claimed in any of the preceding claims wherein the second section of said vent sleeve is capable of supporting a conventional vent or purge pipe.
6. A purge tee assembly as claimed in any of the preceding claims! wherein said body andlor said distal outlet further comprise 0-rings to enhance the seal made by said first and second screw caps.
7. A purge tee assembly as claimed in claim 6, wherein said vent sleeve seals against the 0-ring at said distal outlet.
8. A purge tee assembly as claimed in any of the preceding claims, wherein said vent sleeve comprises a formed bend intermediate said first section and said second section, the bend formed so as to optimise fluid flow.
9. A purge tee assembly as claimed in any of the preceding claims, further comprising a vent pipe for connection to the second section of said vent sleeve.
10. A purge tee assembly as claimed in claim 9, wherein, when connected to said vent sleeve, said vent pipe extends at least one metre vertically above said plastics pipeline.
11. A purge tee assembly as claimed in claim 9 or 10, wherein said vent pipe is metallic.
12. A purge tee assembly as claimed in claim 11, wherein said vent pipe is composed of aluminium or steel.
13. A purge tee assembly as claimed in any of the preceding claims, in which said cutter and said axial bore are screw threaded in a complementary fashion.
14. A purge tee assembly as claimed in claim 13, wherein said cutter comprises a socket for engagement with a complementary tool.
15. A purge tee assembly as claimed in claim 14, wherein said complementary tool comprises a winding tool to translate said cutter along said axial bore.
16. A purge tee assembly as claimed in claim 14, wherein said complementary tool comprises a top loading clamp.
17. A purge tee assembly as claimed in any of the preceding claims, wherein said saddle, body and spigot are integrally moulded.
18. A purge tee assembly as claimed in any of the preceding claims, in which said screw caps are made from plastics material.
19. A method of purging fluid in a plastics pipeline, using a purge tee assembly as claimed in any of the preceding claims, said method comprising the steps of: i) electro-fusing said purge tee assembly to said plastics pipeline; ii) fitting said vent sleeve to the spigot; iD) fitting a vent pipe to said vent sleeve; iv) translating said cutter down said axial bore and cutting a hole in said plastics pipeline; v) translating said cutter upward through said axial bore such that said spigot bore is in fluid connection with said plastics pipeline; vi) venting unwanted fluid from said plastics pipeline; vU) translating said cutter down said axial bore such that said cutter is disposed in said hole to temporarily, at least partially, close fluid connection between said pipeline and spigot bore; viii) removing said vent pipe and vent sleeve; and ix) sealing said purge tee assembly by screwing said first and second screw caps onto said externally threaded end of said hollow body and said distal outlet respectively.
20. A method as claimed in claim 19, wherein said plastics pipeline is scraped to remove nominally 0.2 to 0.4 mm of its surface prior to executing step i).
21. A method as claimed in claim 19 or 20, when using a purge tee assembly as claimed in claim 14, wherein said cutter is translated along said axial bore by rotation of said winding tool when engaged with said socket.
22. A method as claimed in claim any of claims 19-21, wherein said method further comprises the steps of testing the integrity of any seals of said purge tee assembly prior to step ii).
23. A method as claimed in any of claims 19-22, wherein said purge tee assembly is secured to said plastics pipeline by a clamp tool during step i).
24. A purge tee assembly substantially as hereinbefore described with reference to the accompanying drawings
25. A method of purging fluid in a plastics pipeline, substantially as hereinbefore described.