GB2227068A

GB2227068A - Chemically resistant flexible coupling

Info

Publication number: GB2227068A
Application number: GB9000570A
Authority: GB
Inventors: Ernest Peter Geoffrey Smith
Original assignee: LOUGHBOROUGH IND SECURITIES LT
Current assignee: LOUGHBOROUGH IND SECURITIES LT
Priority date: 1989-01-13
Filing date: 1990-01-10
Publication date: 1990-07-18
Anticipated expiration: 2010-01-10
Also published as: GB2227068B; GB8900781D0; GB9000570D0

Abstract

In a coupling for joining pipes used for example for carrying chemical effluents, an elastomeric sleeve 1 has a chemically-resistant resilient lining 6. One or more clamps 3, 4 compress the coupling around the ends of a pair of pipes 10, 11. <IMAGE>

Description

Title : Chemically Resistant Flexible Coupling The present invention relates to a chemically resistant flexible coupling for pipes, in particular, but not exclusively, to such a coupling for use in coupling plain ended pipes in drainage systems.

Effluents discharged in to the drainage systems within chemical plants make considerable demands on the pipeline materials owing to their aggressive nature. Although there are a number of pipeline systems which use a variety of chemically resistant materials or linings, few have fully flexible joints. Hence, there is a tendency for failure of the pipeline within a pipe or at the joints caused by movement due to ground conditions or thermal expansions.

Currently many drainage systems employ a system of pipe jointing requiring the use of resin-based cements which are expensive on constructions costs, dependent on site conditions for curing, and which require high levels of workmanship for a satisfactory joint. The additional and most serious drawback to this rigid jointed system is that superimposed loads and ground movement can cause stress cracking of the buried drain, especially at positions where differential movement arises as between the drain and structures such as manholes.

The problem of rigid joints with chemical drainage are exacerbated as exfiltration through the cracked joints and can lead to serious pollution of the environment, including possible contamination of ground water supplies. The problems associated with rigid joints for drainage pipes generally have been known for a long time. However, flexible mechanical joints have been introduced for domestic sewerage applications, e.g. for sewerage pipes to replace the traditional rigid cement mortar joints.

It is an object of the present invention to provide a coupling which enables pipes, particularly plain-ended pipes to be jointed within a fully flexible mechanical joint which can be used with a range of pipeline systems in new installations, as well as for the repair and renovation of sections of existing drainage installations which have failed.

In accordance with the present invention, there is provided a flexible coupling device for connecting together pipes, tubes and the like comprising an elastomeric cylindrical sleeve having a chemically-resistant resilient lining provided on the inner surface thereof, means being provided for clamping and compressing the sleeve around the ends of a pair of pipes.

The invention provides the following benef its:- 1 All components can be factory manufactured to ensure a high level of quality of control; 2 Ease of site assembly reduces labour costs on site and lessens the possibility of poor site installation; 3 Flexibility ensures that the joint can adjust to minor trench settlement and ground movement and hence reduces the risk of leakage with consequential pollution problems.

Preferably, the sleeve is made from a natural or synthetic elastomer e.g. ethylene propylene diene monomer (EPDM) and the chemically-resistant lining comprises a suitable polymer such as polytetrafluoroethylene (PTFE), fluoro-ethylene polymer (FEP) or another similar fluoropolymer The sleeve is preferably provided with a number of raised annular portions defined on the inner surface thereof so as to provide a sealing effect when the sleeve is contracted around the pipe ends. These portions also assist in the location of the liner and assist in the prevention of cold flow of polymers such as PTFE which could cause a problem in liner failure.

The chemically resistant lining is preferably of unitary cylindrical construction typically a one piece moulding or extrusion located within the sleeve and may extend over all or part of this inner surface of the sleeve and may incorporate a secondary sealing element of expanded PTFE at each end thereof.

The lining can be located within the sleeve either mechanically by virtue of locating ribs or by use of a suitable adhesive or chemical bonding technique. In an alternative, the device can be constructed by coating the liner onto the inner surface of the sleeve or by casting the liner onto the sleeve or vice versa.

The contracting means preferably comprises one or more contracting bands, typically metallic bands which can be contracted by any suitable means such as worm screw or nut and bolt tightening. The bands may be located around the sleeve by means of circumferential ridges provided on the outer surface of the sleeve.

The present invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a part section side view of one embodiment of the invention; Figures 2 show perspective views of embodiments of the invention and 3 employing different means for tightening contracting bands.

Referring now to the drawings, the embodiment shown in Figure 1 comprises a cylindrical elastomeric sleeve (1) which may be manufactured from either a natural or synthetic elastomer such as EPDM, and has a number of circumferentially raised portions (2) positioned along the external width which form defined locations for the external clamping bands (3) (4). A number of raised circumferential ribs (5) (9) are formed on the inner surface of the elastomeric sleeve (1) which provide location, sealing and pressure ribs.

Located within the elastomeric sleeve (1) is a liner (6) which is formed or moulded from a chemically resistant fluoropolymer, such as PTFE or FEP and extends substantially across the internal width of the elastomeric sleeve (1). The chemically resistant liner (6) has across its width a number of rebated ridges and contours (7) (12) which coincide with the location (9) and pressure ribs (5) on the internal surface of the elastomeric sleeve (1) providing positive location of the liner (6) and also to form distinct circumferential sealing areas (8) which effect a pressure contact between the liner (6) and the pipes (10) (11) clamped within the coupling.The pressure ribs (5) ensure that the compressive pressure exerted by the clamping bands (3) is transferred directly through the elastomeric sleeve (1) and the chemically resistant liner (6) to the interface between the pipe surface and the inner surface of the liner sealing areas (8).

In cases where the pipe surface characteristics are difficult to seal onto, a secondary soft compressible sealing element can be included at each end of the liner. The secondary sealing element can be expanded PTFE material which has a compatible chemical resistance.

The central locating rib (9) together with the corresponding rebated contour on the liner (12) also form a central register form pipe location which also prevents the adjacent ends of the pipes (10) (11) from coming into direct contact.

The locating rib (9) and liner contour (12) may or may not be incorporated thereby facilitating use on new work and repair/modifications applications.

The external clamping bands (3) are positioned so as to create, when tightened by screws or worm drive adjustment, a sealing force as a result of compressing the elastomeric sleeve (1) through the internal pressure ribs (5) to the liner sealing area (8) and/or the secondary seal. The single central clamping band (4) as well as providing compression to form a seal between the liner (6) and the pipes (10) (11) also effects a stiffening of the pipe coupling assembly so that whilst not eliminating all the flexibility in the joint, assists in preventing excessive displacement of one pipe relative to the other due to unequal forces exerted on the pipes from the ground or other pipe supporting medium.

Claims

1 A flexible coupling device for connecting together pipes, tubes and the like comprising an elastomeric cylindrical sleeve having a chemically-resistant resilient lining provided on the inner surface thereof, means being provided for clamping and compressing the sleeve around the ends of a pair of pipes.

2 A coupling device as claimed in claim 1 in which the means for clamping and compressing the sleeve is located intermediate the ends thereof.

3 A coupling device as claimed in claim 1 or 2 in which said means comprises one or more clamping bands.

4 A coupling device as in claim 3 in which the or each clamping band is located between two circumferentially raised portions.

5 A coupling device as claimed in any one of the preceding claims in which the sleeve material is a natural or synthetic elastomer.

6 A coupling device as claimed in claim 5 in which the sleeve material is ethylene propylene diene monomer.

7 A coupling device as claimed in any one of the preceding claims in which the chemically-resistant lining comprises a polymer.

8 A coupling device as claimed in claim 7 in which the polymer comprises polytetrachloroethylene (PTFE) or a fluoroethylene polymer (FEP).

9 A coupling device as claimed in any one of the preceding claims in which the lining is of unitary construction.

10 A coupling device as claimed in claim 9 in which the lining is a one piece moulding or extrusion.

11 A coupling device as claimed in claim 9 or 10 in which the lining is mechanically located within the sleeve.

12 A coupling device as claimed in claim 9 or 10 in which the lining is adhered to the sleeve by an adhesive or chemical bonding.

13 A coupling device as claimed in claim 11 or 12 in which a secondary seal is provided at the ends of the lining for engagement with the outer cylindrical surface of each of the pipes to be joined.

14 A coupling device as claimed in claim 9 or 10 in which the lining is coated onto the sleeve.

15 A coupling device in any one of the preceding claims in which a plurality of ribs are provided on the internal surface of the sleeve to form circumferential sealing areas against the outer walls of the pipe ends to be joined.

16 A coupling device as claimed in-any one of the preceding claims in which a generally centrally placed rib is provided within the sleeve against which the open ends of the pipes to be joined abut.

17 A coupling device for connecting together pipes, tubes and the like substantially as herein described with reference to and as illustrated in the accompanying drawing.