AU547093B2 - Hot tap saddle fitting - Google Patents

Description

Title: "HOT TAP SADDLE FITTING"

TECHNICAL FIELD OF THE INVENTION

This invention relates to a method and apparatus for use in connecting pipes and of particular use for connecting a pipe to a gas main while the main is pressurized.

BACKGROUND OF THE INVENTION

In the past pipe connection to a pressurized gas main has been achieved by means of a hot tap saddle fitting. That fitting provides a chamber which is mounted to the main pipe by a collar, the mouth of the chamber seating against the external wall of the pipe and sealing therewith. A drill bit inside the sealed chamber is operable from outside the chamber to drill radially into the main pipe. A subsidiary pipe to be connected with the main is connected to the chamber usually by coupling means integral with the fitting and the drill bit is then operated so as to pierce the main thereby placing the subsidiary pipe in communication with the interior of the main. SUMMARY OF THE INVENTION According to preferred embodiments the present invention provides a hot tap saddle fitting suitable for use with a main pipe made of plastics, and which is of a simpler construction than previously known fittings of the type under discussion.

According to one aspect the invention consists in a hot tap saddle fitting of the kind comprising a chamber having an opening, the mouth of the opening being shaped for sealing engagement with the exterior of a plastics main pipe to be saddled, and piercing means within the^' chamber operable from outside the chamber to pierce the main pipe saddled whereby to place the interior of the main pipe in communication with the chamber, . said saddle fitting being characterised in that the piercing means comprise a cutter acting to cut the main pipe saddled in a chordal direction.

It has been found that by slicing the main in a chordal direction, rather than by drilling into it in a radial direction, a swarf free opening is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only an embodiment of the invention will now be described with reference to the accompanying drawings wherein:-

Figure 1 shows a cross-section of a saddle fitting according to the invention, and

Figure 2 shows a part cross-section on line 2-2 of figure 1. DESCRIPTION OF PREFERRED EMBODIMENTS

The fitting comprises a cylindrical split collar 1 adapted to sleeve a gas main. Collar 1 has a groove 10 on its internal surface extending in a direction parallel the cylinder axial direction and which facilitates hinge opening of the collar for positioning of the fitting to saddle a main pipe. Collar 1 has radially outwardly extending projections 11 adjacent the split whereby the collar may be clamped tightly to a gas main. For preference projections 11 are wedge shaped to facilitate tight clamping to a main pipe by clamp means not shown in the drawings.

An elongate tubular body 3 extends in the direction chordal to the circumference of collar 1 and defines a chamber 4 having an opening the mouth of which is defined by rim 14 which in use seals with a pipe saddled. Tubular body 3 extends to a pipe connection means 5 adapted for connection with a subsidiary pipe. In the present example connection means 5 is a spigot adapted for connection by the joining method described in co-pending application PCT/AU80/00020 but other connection fittings could be used.

Tubular body 3 extends from. chamber 4 in a direction away from connection means 5 to house a hollow tubular cutter 6 which has a cutting edge 61 at the end adjacent chamber 4 of a radius clearance less than the internal radius of tubular body 3.

OM Cutter 6 is closed at the end remote from cutting edge 61- Cutter 6 is provided with O-ring 62 which permits movement of the cutter in the axial direction of tubular body 3 while maintaining a seal between cutter 6 and body 3. Closed end 63 of cutter 6 is provided with groove means 64 for connection of a driving tool (not shown in the drawings) whereby the cutter may be driven into chamber 4 from outside the fitting. Tubular .body 3 is provided with radially inwardly extending shoulders 7 which prevent egress of cutter 6 from that end of tubular body 3.

' In use a solvent, adhesive, or welding means, may be used to ensure a seal between the internal surface of collar 1 adjacent chamber 4 with the outer surface of a mains pipe encircled by collar 1. _ A subsidiary pipe to be tapped to the mains is connected at 5. Tubular cutter 6 is then driven in the chordal direction towards the pipe so as to cut open the pipe and permitting communication between the main and the subsidiary pipe.

For preference the fitting is moulded from plastics for example nylon. The cutter may for example be of steel or a plated steel. As will be readily understood fittings according to. the invention may be made in a variety of sizes and/or with other junctions, unions or valves integral with tubular body 3. The cutter may be slideable or may be fitted with a screw thread enabling it to be driven towards the main by rotation. While it is highly preferred that the saddle chamber be provided

O with means for connecting a subsidiary pipe to the chamber of the fitting, means for making that connection may be manufactured at the time of jointing and need not be part of the saddle fitting itself.

Claims (11)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

1. A hot tap saddle fitting of the kind comprising a chamber having an_.opening, the mouth of the opening being shaped for sealing engagement with the exterior of a plastics main pipe to be saddled, and piercing means within the chamber operable from outside the chamber to pierce the main pipe saddled whereby to place the interior of the main pipe in communication with the chamber, said saddle fitting being characterised in that the piercing means comprise a cutter acting to cut the main pipe saddled in a chordal direction.

2. Apparatus according to claim 1 wherein the chamber comprises an elongate hollow tubular body of which the tubular wall has an opening, the rim of the opening being saddle shaped so that the body may be clamped astride a main pipe with said rim continuously engaging the outer surface of the main pipe and the elongate body extending in a direction which is chordal to the main pipe circumference.

3. Apparatus according to claim 1 or claim 2, wherein the chamber is provided with a generally cylindrical split collar whereby the chamber may be mounted to the main pipe with the rim surrounding the opening of the chamber in sealing engagement with the exterior surface of the main pipe.

4. Apparatus according to any one of the preceding claims wherein the piercing means comprises a hollow tubular cutter.

5. Apparatus according to claims 2 or 3 wh'erein the piercing means comprise a hollow tubular cutter sharpened at an open end and closed at the other end, said cutter sleeved within the elongate tubular body and slideable therein with the sharpened end towards a pipe saddled, and means providing a gas tight seal between the radially outer surface of the cutter and the radially inner surface of the tubular body.

6. Apparatus according to any one of the preceding claims including means for connection of the chamber to a subsidiary pipe to be joined to the main pipe.

7. Apparatus according to claim 6 wherein the subsidiary pipe connection means is a spigot.

8. A method for joining a pipe to a gas main under pressure when the gas main is made from plastics material, said method comprising the steps of: mounting a chamber having an opening so that the mouth of the opening is in sealing engagement with the exterior of the main pipe, said chamber including a cutter operable from exterior of the chamber without gas leakage from the chamber, connecting the pipe with the chamber so that the pipe communicates with the interior of the chamber, and subsequently slicing the main in a chordal direction by operation of the cutter whereby to place the main interior in communication with the chamber and thus with the pipe.

9. A method according to claim 8 further including the step of: mounting the chamber to the mains by means of a split collar.

10. A method according to claim 9 wherein the rim surrounding the mouth of the chamber is welded or bonded to the radially exterior surface of the mains.

11. A method substantially as herein described with reference to the drawings.