GB2250565A

GB2250565A - Sealing within pipes

Info

Publication number: GB2250565A
Application number: GB9026713A
Authority: GB
Inventors: Keith Baylis; Kevin Eric Arnold
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-12-07
Filing date: 1990-12-07
Publication date: 1992-06-10
Anticipated expiration: 2010-12-07
Also published as: GB2250565B; GB9026713D0

Abstract

In order to seal the annular space between an existing gas service pipe (2) and a plastics liner (1) a sealant (5) in the form of a paste or gel is pumped into the annular space from the meter end of the service. The sealant is formulated such that the advancing front of the sealant mass is a wall extending transversely of the pipes (1,2). Various compositions of sealant are described. The parts by weight of a preferred sealant are:- ordinary Portland Cement 100, pulverised fuel ash 0-150, styrene butadiene latex 10-50, water 0-60, plasticiser 0-20. The latex assists in adhering the sealant to the pipes, and the plasticiser assists in the flow of the sealant and helps reduce shrinkage of the cured material. <IMAGE>

Description

SEALING WITHIN PIPES The present invention relates to sealants for sealing an enclosure and particularly to a sealant for use in sealing the annular gap between a pipe and a pipe liner.

The pipe may be employed for carrying liquids or gases. The invention relates particularly, but not exclusively, to lining pipes which are employed for the distribution of natural or manufactured hydrocarbon gases to the users of such.

According to one aspect of the present invention, a method of lining a pipe with a liner comprises introducing a sealant into the annular gap between the pipe and the liner, the sealant being in the form of a paste or gel.

According to a second aspect of the invention, a method of lining a pipe with a liner comprises introducing a sealant into the annular gap between the pipe and the liner, the sealant being formulated such that the sealant can be pumped along the annular gap and such that the advancing end of the sealant mass takes the form of a wall extending substantially transversely of the pipe.

The sealant material is preferably a cement-based composition.

It is preferable that the composition be formulated to exhibit minimal shrinkage on curing and more preferably to expand on curing.

Preferably, the composition is formulated such that the sealant adheres to the surfaces it contacts in the sealing situation. It is also preferable that the sealant is formulated so that when cured it is completely impermeable to gases or fluids. Also it is preferable that the cured sealant has toughness and resilience in order to resist expansion and contraction caused by thermal changes.

The invention will now be further described, by way of example only, with reference to the accompanying drawing, which is a schematic vertical cross-section of an underground gas service comprising a new polyethylene pipe 1 that has been inserted into an existing steel service pipe 2. The polyethylene pipe 1 is intended to transport gas from the gas main 3 to the customer's meter 4. In order to seal the annular space between pipes 1 and 2, sealant 5 is introduced into the annular space by the pump 6, the final position of the sealant being shown at 7.

The reason for lining a gas service pipe is to replace the gas carrying function of the steel pipe 2 (which may actually be weakened or leaking through corrosion) by the polyethylene pipe.

The sealant described herein is designed to be injected into the annular space between the steel and the polyethylene pipe to extend along substantially the entire length of the service.

It is the function of the inventive sealing compound to cause gas from the main to be carried to the meter through the polyethylene pipe and not along the annular gap between the polyethylene pipe 1 and the steel pipe 2. As a consequence of the presence of the inventive sealant, the service function is transferred from the steel pipe to the polyethylene one. The sealant is pumped from the meter end of the service pipe along the annular gap to the main end.

The 'flow' of the sealant, by nature of its gel-like form, along the annular space between the two pipes, should be as a 'plug flow', in which the front of the sealant moves as a single wall, pushing the gas in the annular space before it, the wall extending substantially transversely of the pipes.

The sealant described here is not limited to sealing gas services.

Flow stopping and sealing in a variety of situations can also be undertaken.

A particularly preferred composition of sealant in accordance with the invention is based on cement, particularly ordinary Portland Cement. kowever, other types of cement such as High Alumina Cement can also be used.

An alternative base for the composition is gypsum.

The composition also preferably comprises a latex, or an emulsion of a polymeric compound. This is to impart adhesive properties to the cured compound and also to give it toughness and flexibility. The preferred types of latices can be typically styrene-butadiene, poly vinyl acetate, vinyl acetate-ethylene, vinyl acetate-ethylene-vinyl chloride, vinyl acrylic and Neoprene trade name of the Du Pont Company).

The composition also preferably contains a plasticiser to assist in the easy flow of the sealing compound and to reduce shrinkage of the cured compound. These may typically be, but are not restricted to, lignosulphonates, hydroxylated carboxylic acids and sulphonated melamine formaldehyde.

The composition may also contain extenders preferably, but not restricted to, pulverised fuel ash (PFA). The composition may also contain water to assist in the hydraulic cure of the cement: however this may not be required.

The preferred composition is formulated to give, on mixing the components together, a smooth paste or gel. This mixed material can then readily be pumped or pasted into the desired location. Pumping can be carried out using hand or machine powered equipment such as positive displacement or screw-type pumps.

By way of example only, a suitable formulation may have the following composition: Parts by Weight Ordinary Portland Cement 100 Pulverised Fuel Ash O - 150 Styrene Butadiene latex 10 - 50 H20 0 - 60 Plasticiser O - 20 The composition might also contain cure accelerators or retarders.

It might also contain additional gelling agents such as, but not restricted to, hydroxy ethyl cellulose or bentonite clay.

A typical cured composition cures to a tough compound adhering to steel and other types of pipes.

A third aspect of the invention comprises novel sealant compositions hereinbefore described.

Claims

1. A method of lining a pipe with a liner comprising introducing a sealant into the annular gap between the pipe and the liner, the sealant being in the form of a paste or gel.

2. The method of Claim 1 in which the sealant is formulated such that the sealant can be pumped along the annular gap and such that the advancing end of the sealant mass takes the form of a wall extending substantially transversely of the pipe.

3. The method of Claim 1 or Claim 2 in which the sealant contains gypsum.

4. The method of Claim 1 or Claim 2 in which the sealant contains cement.

5. The method of Claim 4 in which the cement is Portland Cement.

6. The method according to any one of the preceding claims in which the sealant is so formulated that the sealant adheres to the pipe and liner.

7. The method of Claim 6 in which the sealant comprises a latex.

8. The method according to any one of the preceding claims in which the sealant comprises a plasticiser.

9. The method according to Claim 8 in which the plasticiser is from the group consisting of lignosulphonates, hydroxylated carboxylic acids and sulphonated melamine formaldehyde.

10. The method according to Claim 1 in which the sealant has the following composition expressed as parts by weight Ordinary Portland Cement 100 Pulverised fuel ash 0 - 150 Styrene butadiene latex 10 - 50 Water 0 - 60 Plasticiser 0 - 20

11. The method of Claim 1 and substantially as herein described with reference to the accompanying drawing.

12. A method of lining a pipe with a liner comprising introducing a sealant into the annular gap between the pipe and the liner, the sealant being formulated such that the sealant can be pumped along the annular gap and such that the advancing end of the sealant mass takes the form of a wall extending substantially transversely of the pipe.

13. A sealant having the composition, expressed as parts by weight Ordinary Portland Cement 100 Pulverised fuel ash 0 - 150 Styrene butadiene latex 10 - 50 Water 0 - 60 Plasticiser 0 - 20