IL36915A - Sealing of pipes - Google Patents

Description

Sealing of Pipes This invention relates to sealing means, in particular sealing means for gas pipe joints.

A known mothod for sealing gas pipe joints involves the use of .an assembly of plates and bolts to clamp a rubber collar against the joint, the whole assembly of collar, plates and bolts being left on the pipes to maintain the seal.

We have now discovered that a thermo-sensitive material may be used to seal a gas pipe joint by moulding,. so that moulding means for the material may be removed after the joint has been sealed.

According to this invention there is provided a method of sealing >a gas pipe joint comprising applying to the area of the joint a length of thermo-sensitive material which is heated sufficiently before or after application to make it plastic and moulding the length into position to effect the seal.

Where one pipe fits into the flanged end of another pipe, a strip of thermo-sensitive sealing tape may be hea-ted sufficiently to make it plastic, laid on the first said pipe against the flange of the other pipe and then moulded into the angle between the first said pipe and the flange.

The method may be used advantageously where a joint already formed between gas pipes develops a leak and it is desired to form a further seal between the pipes.

Referring to the accompanying drawings :- , Fig. 1 is a section, on one radius only, of a joint to illustrate a known method of sealing a joint between gas pipes; Fig. 2 shows by way of example a cross-sectional shape of one £>rm of sealing taps- according to the invention; Fig. 3 shows in perspective view a strip of tape ' - · -such as that illustrated in Fig. 2 suitable for sealing a gas pipe joint; Fig. shows in cross-section on one radius only the strip o Fig. 3 laid against a gas. pipe joint with moulding apparatus mounted on the pipe ready to make the seal; Fig. 5 shows in cross-section on one radius only the strip and mouldin apparatus of Fi . during. the making of the seal..

Referring to Fig. 1 , there is seen* a male/female joint between gas pipes 10 and 12 of which the centre line is at 13 · A seal 1¾ previously made on assembly of the pipes is assumed to have developed a f'a(L/iH: so that it is leaking. The known method of sealing the joint is to clamp a backing plate 16 behind the flange on the pipe 1 2 . A plurality of threaded "J bolts" 18 (one only shown in the half section of Fig. l) are then attached to this plate. A split rubber collar 20 is . placed around the pipe 10 against the joint l and flanged end of pipe 12 and a split pressure plate 22 slid over the ends of the "J bolts". Each "J bolt" has a nut 2½,on it and by screwing the nuts against the pressure plate, the rubber collar is urged against the flange to effect a seal. ■ Disadvantages of this method are that the rubber 20 is not of itself permanently secured to the joint may destroy the seal, and furthermore the whole assembly has to be left underground with .the pipes.

Referring now to Figs. 2 and 5 there is shown an example of a method and apparatus for sealing a joint between gas pipes in accordance with the invention. In Figs. 2 and 3 there is seen a strip JO of thermo-sensitive material. It is of sufficient length to wrap around one of the pipes so that the ends meet. The strip preferably has scarfe cut ' ends 32 as shown in Fig. 3 » A preferred cross-section for the strip is shown in Fig. 2. It is tri-angular with rounded corners, the triangle having a long side a which is to be laid against the periphery of one pipe. A side b which makes "an angle B preferably between 30° and 15° with the normal to the plane containing the side a is designed to face the joint and flanged end of the other pipe.

As shown in Fig. 4 , a gas pipe 3 has been fitted into a flanged enlarged end 36 of another gas pipe 38 » a conventional packing material 4θ forming the joint. The centre line of the pipes is seen at 35 · It is assumed that the joint 40 has started to leak and a new fluid-tight seal is required.

The. method of sealing in this example is as follows. The length of thermo-sensitive sealant 30 is heated sufficiently to make it plastic. The surfaces of the pipe 34 and flanged end 36 to which the sealant is to . adhere are cleaned by a process such as blasting with an abrasive material and are then primed with an adhesive. . The heated thermo-sensitive strip is then placed around the i e with the side b pressure mould is then put into position against the sealant, and forced up against it thereby effecting a seal. Moulding apparatus for carrying out the method may include mould having a clamping collar securable to a first pipe, and an annular pressure moulding portion in. two or more , segments mounted on the clamping collar which can be urged, e.g. by screw means, towards the thermo-sensitive material to be moulded.

A preferred type of mould 4l has a split pressure-moulding portion 42, shown in Figs. 4 and 5, which is assembled and then held in position by a segmented bracket 44 which is equally assembled around the pipe 3^ an<* is then clamped around the moulding portion 42. These parts 42 and 44 are free to move along the pipe 54. Means for moving the moulding portion into contact with the thermo-sensitive strip include at least tvo threaded studs 46 attached to the bracket 44, one of which is shown in Figs. 4 and 5 running parallel to the pipe, the other stud (not shown) also running parallel to the pipe on the diametrically opposite side of it. Each stud carries a nut 48 which can be screwed up towards a segmented collar 50 against a washer 5 and thrust bearing 54 contacting the collar (Fig. 4). The. collar 50 is slid over the ends of the studs and is then firmly clamped to the pipe by any conventional clampin . arrangement . By screwing the nuts 48 up against, the washer 52, thrust bearing 54 and collar 50 the moulding portion 42 is forced against the thermo-sensitive strip and as great a pressure as possible is maintained until the material of the thermo-sensitive i h leaving the thermo-sensitive sealant sealing the two ^.pes as indicated in Pig. 5.

The mould 42 will be seen to have a suitable form with frusto-conical working surfaces 43 and 5, to. progressively work the sealant axially gainst the end' of the joint 40 and the flange 36 without the formation of air pockets , while also applying radially inward pressure to cause the sealant to adhere to the periphery of pipe 34.

As alternatives to the apparatus above described,, a mould operated by a hydraulic or pneumatic jack may be used in place of one operated by a screw-jack.

Preferably a .thermoplastic material- is used but a curable composition may be used provided it is suitable - for moulding and the temperature required to, cure the- ~ polymer while in contact with the joint does not damage the joint members or does not risk damage to or explosion of materials within the members being sealed and provided also that the physical properties of the cured composition, . as subsequently' discussed, are suitable.

As Examples of thermo-sensitive sealant materials , we have found that general compositions as follows have given good results i - Gompositions of type A (Suitable for up to 5 p.s.i. gas pressure within the pipes sealed). 100 parts by weight of a natural or synthetic (elastomeric ) rubber, .. up to 100 parts by weight of a resinous polymer compatible with the rubber, up to 150 parts by weight of filler, and up to 100 parts by weight of a plasticiser compatible with the rubber (e.g. Dioctylphthallate or Di-isooctylphthallate In a preferred composition of Type A the rubber ^!s butyl' rubber (a copolymer of isobutylene and isoprene or butadiene, containing not more than 3 of the latter) and the resinous polymer is ABS (acrylic nitrile, butadiene and styrene resin). Such compositions are preferably non-curing and withjsuitable formulation may have virtually unlimited shelf life at normal temperatures. In using such compositions, it has been found that a suitable time for heating in an oven is about 30 minutes at "approximately 180°C which makes the material plastic and suitable for moulding to form the seal. In such a case, pressure should be maintained for approximately 10 minutes.

Oompositions of Type B Parts by weight (suitable for 20 p.s.i gas pressure in the pipes sealed).

High visoosity. Polychoroprene (e.g. Neoprene VT.H.V. ex Dupont) 80' Fast crystallisation rate Polychloroprene (e.g. Neoprene H.C. ex Dupont) 20 - 50 Tackifier or Resinous high molecular weight material compatible with the rubber (e.g. Coumarone . Resin) . 0 - 15 illers - Patty acid coated precipitated Calcium carbonate (e.g. Winnafil) 0 - .75 All purpose Furnace Black 0 - 25 Antioxidant (e.g. Octamine) 0 - 5 Processin Aid or Plasticiser (e.g.

Lutrex R or Dioctylphthallate ) 0 - 20 Light Calcified Magnesia 0 - Compositions of type C Parts by weight Butadiene/Acrylic Nitrile Rubber (e.g.

Breon 1041) 100 PVC 55/Nitrile 4 Blend (e.g. Polyblend ' , Winnafil 0 r- 100 ^ All purpose Furnace Black · -Q - 50 Tackifier or Resinous high molecular weight material compatible with the Processing Aid' or Plas/biciser (e.g. Dutrex R or Dioctylp thsllate) ' 0 - 15 Compositions of type D Parts by weight Thermoplastic Black Co-Polymer elastomer (e.g. Cariflex T.R. 1107) 100 Coumarone Resin (e.g. Uecires R.S.85) 0 - 75 Butyl Zimate 1 -Ί. 5 • Preferred heating times to make the composition suitably plastic for moulding are 45 minutes at 100°0 in the case of a composition of Type B and 45 minutes at 160°C in the case of a composition of Type C.

Examples of useful specific compositions of the type_s__set out above are as follows;- ■·.

SPECIFIC FORMULAE Parts by -weight Type A Butyl Rubber 402 ' 100 Filler (S.R.F. Black) 75 Resinous iPolymer compatible with the rubber (e.g. ABS Resin) 15 Plasticiser (e.g. Di-isoctylphthallate ) 10 Type B Parts by weight High viscosity poly-chloroprene (e.g.

Neoprene WHV - ex Dupont ) 80 Fast crystalisation rate polychloroprene e. . Neo rene HC - ex Du ont 2 Filler (all purpose furnace ■ black) · 20 Anti-oxidant (e.g. Octamine-Naugatuch) 2 Processing aid (e.g. Dutrex R) 7ΐ Tackifier or. Resinous high molecular weight material compatible with the rubber- (e.g. Coumarone Resin) 7½ l jiVfc' Calcified Magnesia 4 Type C Parts by weight Butadiene/Acrylic Nitrile Rubber (e.g.

Breon 1041) 100 P.V.C. 55/Nitrile 45 Blend (e.g. Polyblend ■ 503 - e British Geon) 25 Fillers- Winnafil.. 70 AM Purpose Furnace Bla'ck ' 30 Tackifie or Resinous high molecular weight material compatible with rubber (e.g.

Coumarone Resin)- 7½ Processing aid (e.g. Dutrex R) 7s" Composition of Type D Parts by weight Thermo-plastic block co-polymer elastomer (e.g. Cariflex TR 1107) 100 Tackifier or resinous high molecular weight material compatible with' rubber (e.g.

Coumarone Resin M.P. 85eC) 50 Butyl Zimate 1 Advantages of a sealant as above exemplified are its cheapness and ease of application, its ability to follow the cont^ours of any pipe, aid .that the sealant — does not deterxorate either whxle bexng stored prior to use or after the seal has been made. It will also be . apparent that no apparatus needs to be left on the , pipes,. e.g. underground, where deterioration or mechanical interference could take place and the sealing method is an easy one to carry out.

Preferably, the thermo-sensitive material includes a natural or synthetic rubber and may have a resinous polymer compatible with the rubber compounded therewith.

A filler and plasticiser may be included.

The material should be selected according to its intended applicatio so that it has good ageing resistance and chemical inertness to substances likely to come into contact with it. It should also have sufficient elasticity to absorb e.g. contraction and expansion of the joint members and sufficient strength to withstand impacts and applied pressures. It should have sufficiently high modulus or stiffness at all temperatures which it is likely to come into contact with in service.

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Claims (1)

1. WHAT IS CLAIMED IS t 1. A method of sealing a pipe joint comprising a) placing a solid sealant material at a joint between two pipes when in their intended positions b) heating the material c) fitting a removable pressing mould around at least one of the pipes d) applying pressure to one face of the material by movi g a portion of the mould axially along one of the pipes , to force the material into the joint and Impose on the material the configuration of the mould portion, steps a, b, c and d being performed in any order except that a must precede d, e) maintaining the mould portion in contact with the material until a seal is assured as a result of the heating of the material, and f ) removing the mould* 2. A method as claimed in Claim 1 wherein the moulding part is an annulus having a conical flared portion of a diameter increasing in the direction in which the moulding part is moved to exert the said force on the material, the said flared portion surrounding the pipe, whereby the effect of the said forcing is to tend to urge the material radially inwardly as well as axially along the pipe. 3* A method as claimed in claim 1 wherein the joint is a pre-existing joint with an exposed ring of preexisting sealing material, the solid sealant material being placed adjacent the said ring and being forced into contact with it, whereby to form sealing engagement with it as well as with the two pipes. k» A method as claimed in claim 1 wherein the sealant material has a triangular cross-sectional shape when first placed in position. 5. A method as claimed i claim wherein the sealant material is in the form of a uniform continuous js trip, and is cut to length before being placed in position. 6. A method as claimed in claim 1, when applied to rosea ling or improving. a pre-existing seal between pipes having respectively a pipe end and a pipe socket to render it pressure-resistant, without interrupting any flow through the pipes, comprising a) cutting a preformed, uniform, strip of thermoplastic material to length to fit around the pipe having the pipe end b) heating the cut length of strip to soften it c) placing the softened strip around the pipe having the pipe end adjacent the pre-existing seal element and placing a removable mould around the said pipe d) operating the mould to cause a moulding portion to press the softened strip against the preexisting seal and between the pipe end and the pipe socket to be deformed from its pre-formed shape e) maintaining the said pressure until the strip, is in pressure-resisting sealing condition and f) removing the mould* 7. Method of sealing a pipe joint substantially as hereinbefore described. 8. Pipe joints whenever effected in accordance with any of claims 1 - 6· \ COHEN ZEDEK & SPISBACH P.O. BOX 33116 , TEL AVTV. APPLICANTS ATTORNEYS