WO2005059421A1

WO2005059421A1 - Pipe seal

Info

Publication number: WO2005059421A1
Application number: PCT/GB2004/005375
Authority: WO
Inventors: John Reginald Newton
Original assignee: STRUCTURAL SCIENCE Ltd
Current assignee: STRUCTURAL SCIENCE Ltd
Priority date: 2003-12-17
Filing date: 2004-12-17
Publication date: 2005-06-30
Anticipated expiration: 2006-06-17
Also published as: GB0329267D0

Abstract

A pipe seal comprising a main body portion adapted to be fixed to a wall, the wall comprising a plurality of wall members having an interstitial space, a part spherical seal body mounted for rotational movement within the main body, the part spherical body including a seal adapted to deform and engage a pipe, the seal including a member including an aperture, the seal body including a conduit communicating between the aperture and clamping means, the clamping means being adapted to connect the pipe seal to said wall members so that the conduit communicates with said interstitial space.

Description

PIPE SEAL

This invention concerns a pipe seal, and more particularly relates to a seal for a pipe entering a double walled chamber.

Throughout industry there are many examples of pipes and cables terminating at equipment housed within tanks or chambers. Typically these chambers are thin- walled and at the point of entry the pipe is sealed to the tank wall. In installations where the tank or chamber is below ground level, there is a need to seal the pipe to prevent the ingress of ground water. More recently, in view of environmental legislation, it has become increasingly important to ensure that any chemicals, held within or spilled within the chamber, are contained and do not enter the ground and cause contamination.

In order to meet environmental and safety standards, many chambers, particularly those used in petrol station forecourts, are now double- walled, and indeed many pipes entering such chambers are double-walled also. The interstitial spaces can be checked to ensure that there is no leakage either of groundwater into, or fuel out of, the system. Ideally, the interstitial spaces should be continuously monitored from a remote location, e.g. the kiosk in a petrol station forecourt.

Pipes entering a chamber either connect to equipment within the chamber or form a junction with other pipes. In either case it is not always possible for the pipe to enter at 90 degrees to the chamber wall.

In our WO2004/001268, there is described a pipe seal which comprises: a main body portion adapted to be fixed to the wall of a chamber, tank or the like; a face plate adapted to be secured to the body portion to surround, in use, a pipe to be sealed; the body and face plate between them housing a deformable member in contact with a seal; such that, on forcing the plate toward the body portion, the deformable member, in use, deforms and presses the seal into sealing contact with the pipe; and having a port which, in use, is connectable to the interstitial space of a double walled container. The design of this pipe seal allows the integrity of the system to be tested by various methods. In a preferred method, vacuum can be applied to the interstitial spaces of any specific group of seals and pipes, and the rate of decay monitored thereby allowing the integrity of the system to be established. This method is described in European patent EP-A- 0875746 and is especially suitable at the point of installation owing to the very short test times, typically of the order of one minute.

In many jurisdictions, for example in the United States, much more stringent regulations are coming into force and in many places legislation now requires that this type of seal is monitored for leakage on a continuous basis throughout its life. The monitoring may be by a fluid or vacuum based system. Where the desired flexibility of the seal to accommodate at angles other than 90 degrees is present, then a rubber bellow seal is often employed clamped to the seal body, attached to the chamber and then clamped to the pipe. While seals of this type are very effective at providing the rotational movement, they are a source of weakness as the rubber deteriorates over time, has limited chemical resistance and is prone to physical damage. Furthermore, a rubber bellows type seal is not suitable to contain pressure or the level of vacuum that would typically need to be used to continuously monitor the fluid tightness of the seal.

The invention seeks to provide a seal for a double walled tank improved in the above respects. According to the present invention, there is provided a pipe seal which comprises a main body portion adapted to be fixed to a wall, the wall comprising a plurality of wall members having an interstitial space, a part spherical seal body mounted for rotational movement within the main body, the part spherical body including a seal adapted to deform and engage a pipe, the seal including a member including an aperture, the seal body including a conduit communicating between the aperture and clamping means, the clamping means being adapted to connect the pipe seal to said wall members so that the conduit communicates with said interstitial space. Preferably, two or more seals are provided separated by a spacer, the spacer having a conduit or channel connecting to the interstitial space of the double walled container. The advantage of this construction is that, if either of the seals fail, the monitoring system is alerted while the remaining seal ensures that there is no spillage of contaminant. The preferred method of monitoring is to connect the monitoring system to the interstitial space of the chamber wall and hence connection is made to all the pipe seals fitted to that particular chamber.

In a preferred embodiment, a valve arrangement may be provided, for example a needle valve, whereby to isolate each seal to assist in locating one that might be leaking. The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a front elevational view of the pipe seal as seen from inside the chamber;

Figure 2 is a cross-sectional view on line X-X in Figure 1 ;

Figure 3 is a cross-sectional view on line Y-Y in Figure 1; and Figure 4 is a cross-sectional view on line Z-Z in Figure 1.

Referring to the drawings, a pipe seal in accordance with the invention comprises a main body 1 which houses a central part-spherical body 2. The part-spherical body 2 has a central bore for receiving a pipe 9, and the bore is provided with a recess 3 to accommodate a pair of radial seals 4 separated by a spacer 5. A compression ring 6 is provided having a series of socket head cap screws 7 located in inserts 8 moulded into the part-spherical body 2 so that on tightening the screws 7 the compression ring 6 compresses the radial seals 4 both against the pipe 9 and the faces of the recess 3 ensuring sealing engagement. The body 2 is held within the main body 1 and is sealed thereto by O-ring seals 18 and 22. The spherical body 2 is held in place in the main body 1 by means of an inner clamping ring 19 which has a series of socket head cap screws 20 located circumferentially around it which mate with inserts 21 moulded into the main body 1 and, when tightened, clamp the central spherical body 2 to the main body 1. The inner clamping ring 19 carries the O-ring seal 22 which seals against the central part-spherical body 2. A further seal 23 (Figure 4) is provided between the inner clamping ring 19 and the main body 1 and provides a seal for the socket head screws 20.

A circumferential flange 28 on the outer edge of the main body 1 abuts against the wall 27 of the chamber, tank ,or the like and is provided with a seal 29. An outer clamping ring 30 is provided, having a series of socket head cap screws 31 located circumferentially around it which mate with inserts 32 moulded into the main body 1. An O-ring seal 33 seals the outer clamping 30 to the inner clamping ring 19, and a seal 34 is provided between the face 35 of the outer clamping ring 30 and the chamber wall 27. Tightening the screws 31 clamps the seals 29 and 34 and the wall 27 of the chamber tightly together.

The central spacer 5 has a number of holes 10 connecting its inner 11 and outer 12 surfaces connecting with a hole 13 in the spherical body 2. A needle valve 14 is provided in the central body 2 which can be used to close off the hole 13. Also located in the hole 13 is a hollow pin 15 which extends beyond the outer spherical surface 16 of the part-spherical body 2. The hollow pin 15 locates in a groove 17 formed in the main body 1 and restricts circumferential movement of the part-spherical body with respect to the longitudinal axis to an angular movement of 20 degrees within the main body 1. The main body 1 also has a cross hole 24 connecting the groove 17 to an outer location surface 25 which in turn connects to the interstitial space of the chamber wall 27. Thus, the space between the seals 4 is connected to the interstitial space 27. If desired, the hole 24 may have a needle valve 26 (similar to needle valve 14) which can be used to close it off.

The main body 1, central part-spherical body 2, central spacer 5, compression ring 6, inner clamping ring 19 and outer clamping ring 30 are preferably formed from moulded thermoplastic material incorporating glass fibre reinforcement to provide additional stiffness and enhanced long term grip qualities.

The two radial seals 4 are preferably made of PTFE and glass braided cord which is wrapped several times around the pipe. This seal material has excellent chemical resistance properties while also permitting a degree of axial and radial movement without loss of sealing properties. This type of seal can be replaced without disturbing the pipes.

The O-ring seals 18, 22 and 33 are preferably made of an elastomeric type material, typically a nitrile rubber or "Niton" (Registered Trade Mark) material. The seals 23, 29 and

34 may also be made from an elastomeric material, this time typically a nitrile rubber, " Alcrin" (Registered Trade Mark) or "Pellethene" (Registered Trade Mark) material. The choice of seal material is determined by the specific chemicals encountered in any given application.

The screws, inserts, valve and hollow pin 15 are preferably made of a metal such as stainless steel or brass to provide good chemical resistance.

The pipe seal of the invention may be installed into the wall 27 of a tank and sealed to the pipe 9 as follows.

A single hole 37 of the correct size to match the pipe seal main body 1 is cut into the chamber wall 27 in a location which is as close as possible to the portion within the tank to which the pipe is to be connected, to allow the pipe to pass through the tank wall at an angle as close to right angles as possible. The outer clamping ring 30 and seal 34 are removed, allowing the assembly to be located in the hole 37, after which the outer seal 34 and clamping ring 30 are replaced and the screws 31 tightened sufficiently to still allow the pipe seal assembly to rotate within the hole 37.

The pipe 9 to be sealed is passed through the pipe seal assembly and attached to the appropriate termination point within the chamber. In undertaking this operation, the pipe seal will have been rotated within the hole 37 and the angle of the central part-spherical body 2 adjusted to align the pipe seal assembly with the angle of entry of the pipe 9. Once aligned, the pipe seal assembly is clamped tight and sealed to the chamber wall 27 by tightening the screws 31 fully.

The pipe 9 is then sealed to the assembly by tightening the screws 7, which cause the compression ring 6 to compress the two radial seals 4 within the recess 3, thus creating a fluid- tight seal.

The central part-spherical body 2, which should be clamped during factory assembly just sufficiently to allow it still to move, is now clamped and sealed to the main body 1 by tightening the socket cap screws 20.

The hollow pin 15 extends radially beyond the external diameter of the part-spherical body portion 2 so that an end thereof extends into the groove 17. This arrangement penriits the spherical body 2, and hence the pipe 9, to rotate within the main sealed body 1 from 0 to 20 degrees. At 90 degrees to the radial axis of the pin 15, the spherical body is free to rotate but is restricted by the pipe coming into contact with the rear edge of the main seal body, and rotation is limited to plus or minus 20 degrees also. The main seal body can be rotated through 360 degrees and combining these motions allows the pipe entering the chamber to occupy any position within a cone of movement having an included angle of 40 degrees, hi situations where a smaller pipe is accommodated, then a rim may be provided around the rear edge of the spherical body portion which restricts the radial movement thereof to 20 degrees. Any alternative angular movement of the body portion may be permitted. As already described above, the holes 10 in the central spacer 5 are connected via the passageway 13, pin 15, groove 17, hole 24 and space 25 to the interstitial space of the wall 27. The preferred method of monitoring the integrity of the system is to connect the monitoring system to the interstitial space of the chamber walls 27 and hence connection is made to all the pipe seals fitted to that particular chamber. The needle valve 14 can be closed by means of a screwdriver to isolate the area of the seals 5. If the monitoring system still shows a leak, then it is unlikely to be the seals 5. Similarly, the needle valve 26 can be closed, thereby shutting off the passage 24 and if the monitoring system still shows a leak then it is unlikely to be the O-rings 18,22. This process can be repeated on all of the pipe seals on a given tank until the leak is isolated, after which it can be repaired.

As mentioned above, the use of two seals ensures that if one fails, the monitoring system will be triggered without contaminant necessarily passing through the seal as a whole, since the second seal should contain any leakage. The vacuum of the monitoring system normally used precludes the use of rubber bellows seals, but the seal of the invention will withstand the pressures employed, hi the event that a single wall chamber is deployed and hence no interstitial space is available, the pipe seal can be monitored by removing one of the needle valves and replacing it with a comiection to the monitoring system. Some of the chambers to which the pipe seal will be fitted may be made from a thermoplastic material such as high density polypropylene. Such a material is suitable for thermal welding and this method may be used to attach the pipe seal to the chamber wall by removing the seal 29 and incorporating heating elements to the circumferential flange 28 of the main body 1. If required, seals 34 could also be removed and heating elements incorporated into the face 35 of the outer clamping ring 30.

The pipe seal of the invention offers a number of advantages: the seal can accommodate constant monitoring systems connected through the interstitial space created by a double walled chamber or by direct attachment to the seal; needle valves are provided to assist leak detection and isolation; a pipe can enter a thin walled chamber at an angle of up to 20 degrees from a right angle with the chamber wall throughout a full 360 degrees and be effectively sealed; the pipe seal requires only a single hole to be provided in the chamber wall; the seal in contact with the pipe has a high degree of chemical resistance; the pipe will remain sealed if axial or radial movement of the pipe occurs; the pipe seal has a thin cross-sectional profile and projects a minimum amount into the chamber relative to the pipe diameter; and the outer face of the pipe seal, which can be in contact with the ground, is free of metallic components.

Claims

CLAΓMS

1. A pipe seal comprising a main body portion adapted to be fixed to a wall, the wall comprising a plurality of wall members having an interstitial space, a part spherical seal body mounted for rotational movement within the main body, the part spherical body including a seal adapted to deform and engage a pipe, the seal including a member including an aperture, the seal body including a conduit communicating between the aperture and clamping means, the clamping means being adapted to connect the pipe seal to said wall members so that the conduit communicates with said interstitial space.

2. A pipe seal as claimed in claim 1, comprising a plurality of annular seals separated by said member.

3. A pipe seal as claimed in claim 1 or 2, wherein the member comprises a spacer including a channel communicating with said conduit.

4. A seal as claimed in any preceding claim, including a valve adapted to close the conduit between the seal and interstitial space.

5. A seal as claimed in claim 3 or 4, wherein the spacer includes a multiplicity of apertures connecting the radially inner and outer surfaces of the spacer to the conduit.

6. A seal as claimed in any preceding claim, wherein the central body includes a hollow pin, having a bore, an end of the hollow pin extending radially outwardly of an outer spherical surface of the part spherical body wherein the end of the pin is received in a groove in the main body, the bore and groove comprising part of said conduit.

7. A pipe seal as claimed in claim 6, wherein movement of the pin within the groove limits circumferential movement of the part spherical body.