(54) PIPE JOINTS AND CONNECTORS THEREFOR(71) We, PIPELINE SEAL ANDINSULATOR COMPANY LIMITED, aBritish Company, of Davis House, 8 ScrubsLane, London NW10, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to pipe joints and connectors therefor. More particularly, it relates to pipe joints and connectors for incorporation into pipelines in which the connected pipes are to be electrically insulated from one another.
In United Kingdom Patent SpecificationNo: 1,423,169 there is disclosed a pipe connection in which two aligned pipes are electrically insulated from one another by an annular element of insulating material abutting the pipe ends. A casting of electrically insulating material surrounds the element and the pipe ends to secure the connection.
The present invention is directed to the creation of a pipe connection in which two pipe ends to be electrically insulated from one another terminate in tubular connecting members which telescopically engage. An insulating material is cast in the tubular passage between the telescoping members, to secure the connection and maintain the electrical insulation.
According to the present invention a connector for a pipe joint comprises inner and outer tubular connecting members, end lengths of which are telescopically engaged to define a tubular passage therebetween, the external surface at the end of the inner member and the opposed internal surface portion of the outer member being polished; an O-ring of electrically insulating material located between the members and contacting said opposed polished surface portions to provide a seal therebetween; and a jointing compound of electrically insulating material, cast against the O-ring and the opposed surfaces of the connecting members defining said tubular passage to hold the members relative to one anotherand provide electrical insulation therebetween. The jointing compound preferablycomprises an epoxy resin and a suitablehardener.
In the manufacture of the connector, theO-ring serves two purposes. First, it maintains the end of the inner member spaced from the outer member prior to and during delivery of the jointing compound to the tubular passage and second, by closing the tubular passage it defines a boundary of the casting space. Preferably, the O-ring is formed in neoprene. If desired, a furtherO-ring may be used to close the other end of the tubular passage and thereby enhance the stability of the joint.
The opposed surfaces of the connecting members defining the tubular passage areprepared to receive the O-ring or O-rings and the jointing compound. Thus, the externalsurface of the inner member is polished overthe area or areas thereof which are toengage the or each O-ring as is thecorresponding area of the internal surfaceof the outer member. Such a polished areaon the inner or outer member may be in arecess to assist in locating the O-ring. Forexample, the surface might be machined toform a shoulder defining the extent to whichthe O-ring may be moved down the tubularpassage. At least a portion of the remainingsurface areas may be roughened by forexample sandblasting or machiningserrations thereon, to improve theadherence of the sealing means thereto.
The space defined by an end of onemember, the adjacent O-ring and the othermember may be filled with an electricallyinsulating material. Sufficient material maybe used to provide a smooth transition fromone connecting member to the other.
Internally of the connector, the material ispreferably nonhygroscopic to inhibitmoisture from collecting.
The connecting members will normallyeach comprise a length of cylindrical pipe.
In one embodiment of the invention the inner member is a cylinder of substantially constant diameter and the outer member has an integral enlarged portion which overlaps part of the inner member. In a second embodiment the enlarged portion of the outer member is a separate cylindrical member which is joined, for example by welding, to the larger end of a frusto-conical portion of the remainder of the outer member.
In a third embodiment the connecting members provide a mechanical interlock therebetween which prevents the members from being axially separated in at least the parting direction after they have been assembled together. Such an interlock may be provided by enlarging the external diameter of the inner member towards its said end to at least the normal internal diameter of the outer member and enlarging the internal diameter of the outer member adjacent the end of the inner member.
The invention also provides a pipe joint incorporating a connector as described above in which each member of the connector is joined to the end of a respective pipe length. Further, in some embodiments, one or each of the members of the connector may itself be an end length of one of the pipes.
Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a first connector for a pipe joint, part cut-away;Figure 2 is a similar view to Figure 1 of a second connector; andFigure 3 is a similar view to Figure 1 of a third connector.
Each embodiment of connector is for making a joint between two pipe lengths (not shown) to which a respective member of the connector may be secured in a manner which precludes separation of the members and leakage of the joint and provides an electrical break between the members and thereby the pipe lengths.
Referring to Figure 1, the connector comprises two concentric, cylindrical members 10, 11 in overlapping relation with the outer member 10 radially spaced from the inner member 11. The outer member 10 has an end portion 12 which has been enlarged by bulging. The outer surface of the inner member 11 has an end section 12 which is machined to reduce its diameter and polished to provide a smooth seating 13a for an O-ring sealing member 13 formed, for example, of neoprene. The remainder of the outer surface of the inner member 11 which is overlapped by the outer member 10 is sandblasted and degreased to provide a roughened surface. Also, in this embodiment, part of this roughened surface has serrations 14 thereon. Corresponding polished and roughened sections are provided on the inner surface of the outer member 10, the polished section 15 providing an external seating for the O-ring 13.
Within the annular space defined by the roughened sections of the members 10, 11 is cast a jointing compound 16 comprising a mixture of an epoxy resin and suitable hardener, which holds the members together and prevents relative axial movmement.
A non-hydroscopic filler 17 is also inserted into the connector, the filler forming an annular ring on the other side of the O-ring 13 from the jointing compound 16 to prevent moisture collecting in the pocket formed by the enlargement of the outer member 10 adjacent the inner end of the inner member 11.
In use, the O-ring 13 is inserted into the outer member 10 before assembly of the members 10, 11 and then, whilst the members are held in their desired overlapping relation, the O-ring is pushed into engagement with the smooth sections of the members by a tool inserted into the open end of the outer member. The connector is then inverted with the inner member 11 uppermost, and the jointing compound 16 is dispensed between the members. The filler 17 is then inserted into the connector and, in this embodiment, is caused to fill the above-mentioned pocket formed by the frusto-conical central portion 18 of the outer member 10. The members 10 11 are thereby connected together in a manner which prevents their separation axially and leakage through the joint. Each of the O-rings, jointing compound and filler is electrically insulative and hence, the members are also electrically isolated from each other.
The connector is intended to be used in a low pressure gas pipeline, operating for example, at 30 lb/sq in. While each pipe length might be of any suitable material, the described embodiment is especially useful in making a connection between two steel pipes or between a steel pipe and a cast iron pipe. As shown, the inner member 11 may be formed of cast-iron and have a peripheral groove 19 adjacent its free end for reception of the circlip of a known starlock flexible coupling for connecting another cast-iron pipe length thereto STARLOCK is a registered Trade Mark). The outer member 10 is formed of steel and, at its free end, is welded to the steel pipe length.
Figure 2 shows a second connector having the same basic construction as the connector of Figure 1 and so only the differences will be described. In this case, the members 20, 21 are both formed of steel for welding to respective steel pipe lengths.
The outer member 20 is also formed of two separate sections 22, 23 welded together at 24, the section 22 forming the part which overlaps the inner member 21 and the section 23 forming the free end of the outer member and the frusto-conical part 27 formed by bulging and having a maximum diameter equal to the diameter of the cylindrical section 22. The internal surface of the section 22 is prepared before the sections 22, 23 are welded together, to provide the polished and roughened areas as before. However, in this embodiment the polished external seating for the O-ring 25 is formed by machining and polishing a counterbore 26 in the appropriate end of the cylindrical section 22.
The embodiment of connector shown inFigure 3 is again for joining together two steel pipe lengths and the outer member 30 is formed of two sections 32, 33 welded together at 34. In this embodiment the main difference from the connector of Figure 2, is that a mechanical interlock is provided between the outer and inner members 30, 31 which precludes separation of the members in the axial direction after assembly of the members together. This interlock is formed by enlarging the inner end of the inner member 31 and by providing a corresponding contraction of the free end of section 32 of the outer member 30. A true mechanical interlock between the members without the jointing compound is established if the enlarged external diameter of the inner member 3 is greater than the normal internal diameter of section 32.
However, similar advantage can be gained if the enlargement is only small; i.e., to less than or equal to the normal internal diameter of the section 32. Once the jointing compound 37 is set, separation of the members 31 and 32 will compress the compound, such separation being thereby resisted.
There are also provided two O-rings 35, 36 between the overlapping portions of the members, one at either end of the jointing compound 37. This means that two polished surfaces and an intermediate roughened surface are provided on the outer surface of the inner member 31 and the inner surface of the outer member 30, and in this embodiment the polished surface adjacent the free end of the outer member is provided by machining a counterbore 38 at that end. The purpose of providing the second outermost O-ring 36 after insertion of the jointing compound 37 is to resist any tendency for the jointing compound to crack due to vibration of the pipeline into which the connector is fitted.
Finally, in this embodiment, the filler 39 adjacent the inner O-ring 35 does not fill the whole pocket formed by the frusto-conical portion 40 but merely forms a fillet which fills the end of the annular space between the members 30, 31. Further filler 41 is also provided on the outside of the outer O-ring 36, again to complete the filling of the space between the overlapping members 30, 31.
The invention is not restricted to the specific details of the embodiments described above. For example, either of the embodiments of Figures 1 and 2 may be provided with the mechanical interlock and/or the second O-ring of the embodiment of Figure 3.
Similarly the embodiment of Figure 3 may be modified by omitting the second O-ring 36 in which case the filler 41 would also be omitted, that end of the annular space between the members 30, 31 being filled with jointing compound 37. The filler 39 may also be increased to fill the pocket formed by the frusto-conical portion 40 in like manner to the embodiments of Figures 1 and 2. Alternatively, the filler of the embodiments of Figures 1 and 2 may be reduced in like manner to the embodiments of Figure 3.
The main advantage of providing the mechanical interlock of the embodiment ofFigure 3 is that if the jointing compound should fail, the members of the connector cannot separate and the joint will not leak due to the existence of at least the innerO-ring 35. This is important, if the connector is used in high pressure gas pipelines, at working pressures of for example 700 Ib/sq in. or more.
WHAT WE CLAIM IS:1. A connector for a pipe joint comprising inner and outer tubular connecting members, end lengths of which are telescopically engaged to define a tubular passage therebetween, the external surface at the end of the inner member and the opposed internal surface portion of the outer member being polished; an O-ring of electrically insulating material located between the members and contacting said opposed polished surface portions to provide a seal therebetween; and a jointing compound of electrically insulating material cast against the O-ring and the opposed surfaces of the connecting members defining said tubular passage to hold the members relative to one another and provide electrical insulation therebetween.
2. A connector according to Claim 1 including a further O-ring of electrically insulating material adjacent the end of the outer member substantially closing the other end of the tubular passage between the members.
3. A connector according to Claim 1 orClaim 2 wherein the annular space defined by a said end of one member, the adjacentO-ring and the other member is filled with
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