GB2131909A - Pipeline grout coating and grout bags therefor - Google Patents

Abstract

A circumferential grout coating is formed around a length of recumbent pipe (2) in situ by disposing a lifting grout bag (8) under the said length of pipe, completing a sleeve around the said length of pipe by covering its remaining circumferential surface with at least one further grout bag (10) and securing together the juxtaposed edges of adjacent grout bag walls which form the outer circumferential surface of the sleeve, filling the lifting grout bag with fluid to lift the said length of pipe to a desired ground clearance, filling the grout bags with grout (9), and allowing the grout to set, the said grout bag walls (11) forming the outer surface of the sleeve being permeable to water but substantially impermeable to grout fines and the inner surface (14) of the sleeve being essentially grout- permeable. <IMAGE>

Description

SPECIFICATION Pipeline grout coating and grout bags therefor This invention relates to the in situ grout coating of recumbent pipes -- i.e. pipes lying on or in the ground, e.g. in atrench or on the sea-bed. Itis particularly useful for the repair of an underwater (e.g. sea-bed) pipeline whose grout coating has been damaged or destroyed over a substantial length, but is applicable to the in situ formation of an original or replacement grout coating fully around recumbent piping in general, on land as well as underwater.

Sea-bed pipelines, e.g. for gas or oil, generally have a bituminous protective coating which is in turn protected by an outer grout coating applied and set before laying of the pipes. This outer coating, which also constitutes a weight coating to maintain the pipeline in position, is frequently damaged, e.g. by engagement with ship' anchors; small gaps and cavities are readily plugged by local grout application, but there has been no satisfactory method for replacing the grout coating over a substantial length of pipes is necessary when such a length is removed by collision with aship's hull or disintegrates due to failure to repair smaller areas of damage.Prior methods have generally involved simply laying preformed members over the length to be re-covered, but this is a difficult operation and the preformed members tend too easily to be dislodged and slide partially orfully off the pipe under environmental forces or on collision with a ship's hull or anchor etc.

Accordingtotheinventionacircumferential grout coating is formed in situ around a length of recumbent pipe by disposing a first grout bag under the said length of pipe, completing a sleeve around the said length of pipe by covering its remaining circumferen tial surface with at least onefurther grout bag and securingtogetherthejuxtaposed edges of adjacent grout bag wallswhich form the outercircumferential surface ofthe sleeve, filling the first grout bag with groutto lift the said length of pipe to a desired ground clearance, filling the said further grout bag or bags with grout, and allowing the grout to set, the said grout bag walls forming the outer surface ofthe sleeve being permeable to water butsubstantially imperme able to grout fines.

The said first grout bag may be filled to lift the corresponding length of pipe before or after application of the said further grout bag or bags, but usually before the filling of the latterwith grout. The securing together of the juxtaposed edges of adjacent grout bags which form the outer sleeve surface is normally effected before filling ofthe said further grout bag or bags and may for example be by way of heavy duty zips. Instead offilling the said first bag with grout to lift the corresponding length of pipe, the bag could firstly be filled with another fluid, preferably water, to effect the lifting, the grout being introduced later- e.g. after formation ofthe remainder ofthe sleeve orjacket.

The said first bag used to effect lifting will usually have its contents sealed from communication with the contents ofthe further bag or bags, and at least in the cases where it is initially filled with grout the latter may be allowed to set before grout filling of the further bag or bags. The possibility is not excluded, however, of a system permitting some grout communication between first and adjacentfurther grout bags to render the set sleeve integral in this region.Where there are two or more of the further grout bags these will preferably be secured together externally (e.g. by heavy duty zipping) to provide a grout-tight outer sleevewall, but provision will preferably be made for grout flow between the interiors of the further bags so thatthesetgroutsleeveorjacketextends integrally therethrough.

The said first grout bag (which could of course be replaced by a plurality ofsmallersuch bags secured externally to themselves and to adjacent further grout bags) may extend the full length ofthe pipeto be treated; in other cases it may extend only partiallythis length or there may be used a plurality of longitudinal Iyspacedfirstgrout bags; in these latter cases the filling ofthefirst bag or bags to lift the pipe can give sufficient unobstructed clearance between the ground and the remainderofthe pipe length for the further grout bag or bags to extend fully around this remaining pipe portion.

The or each said further grout bag is preferably compartmentalised by internal walls allowing sub stantial ly free grout movement therethrough.

The invention is illustrated, byway of example only, in the accompanying drawing which is a schematic side elevation, partly in section, of a length of sea-bed pipeline provided with a sleeve.

The singlefigure of the drawing shows a bitumencoated pipe 2 which whilst on the sea-bed 4 has been provided according to the invention with a weight coating 6. The first step in the in situ application of the weight coating is the insertion in a pre-formed clearance between sea-bed and pipe of an empty lifting bag 8whose walls are pervious to water but not to g rout fines. The bag 8 may have rig id inserts tapering inwardlyfrom its longitudinal edges. The lifting bag 8 is then filled under pressure with grouts via an injection pipe (notshown), lifting the pipe to give a desired ground clearance, and the grout may then be left to set.Afurther bag 10 is wrapped around the pipe, the outer wall 11 of this further bag being secured to the lifting bag 8 by a heavy duty zip 12; the abutting longitudinaledgesoftheouterwall 11 ofthe bag 10 wrapped around pipe 2 are also joined in grout tightfashion by an axially extending zip (not shown).

The bag 10 is of quilted appearance and divided into compartments by internal walls 14 of open mesh fabric and is tightened around pipe 2 by straps 16. A furtherwrap-around bag 10 could be secured to either end of the indicated bag by a heavy duty circumferen tialzipjoiningtheiradjacentouterwallsll.

The main bag 10 is provided with a grout injection pipe 18 and a venting pipe 20, and once secured to itself and to bag 8 is filled with grout9to complete the sleeve, the grout passing through the internal walls 14 to fill all of the bag compartments. If another bag 10 The drawing(s) originally filed was informal and the print here reproduced is taken from a later filed formal copy.

around pipe2 is secured to an end ofthe illustrated bag,there may be groutflowthrough the abutting or adjacent internal walls ofthetwo bags. Instead ofthe arrangement shown, the lifting bag 8, or a series of such bags, may extend the full length ofthe pipe to be coated, or lifting bags 8 may be spaced longitudinally along the pipe.

The grout-permeable wall 14 of bag 10may for example be an open mesh fabric of polyamide yarn; it will usually have a minimum weight of 110 gms. per sq. metre and preferably has a tensile strength of at least 800 N/Sc. in both warp and weft direction with an elongation of 25%.The outerwall 11 of bag 10 (and also the wall of lifting bag 8) should preferably have a water permeability of about 15 litres persq. metre per second under a 10cm. head, but be substantially impermeableto groutfines; it may for example be of firmly woven polyester yarn with a minimum weight of 200 gms. per sq. metre; its tensile strength is preferably at least 1500 N/5 cms. in both warp and weft directions with an elongation of 15%.

The present invention resides not only in the indicated method of group coating, but also in the securable (e.g. byzipping) lifting and mainjacketing grout bags which are employed in performing the method. Whilst the method has been described forthe application of a grout coating to a sea-bed pipeline, it is similarly applicable to pipes on land. the grout employed may be a simple sand/cement blend, or one containing ballast or (especiallyforweight coatings) one containing barytes orthe like.

CLAIMS (Filed on 18th October 1983) 1. A method offorming a circumferential grout coating around a length of recumbent pipe in situ by disposing a lifting grout bag underthe said length of pipe, completing a sleeve around the said length of pipe by covering its remaining circumferential surface with at least one further grout bag and securing together the juxtaposed edges of adjacent grout bag walls which form the outer circumferential surface of the sleeve, filling the lifting grout bag with fluid to lift the said length of pipe to a desired ground clearance, filling the grout bags with grout, and allowing the groutto set, the said grout bag walls forming the outer surface ofthe sleeve being permeable to water but substantially impermeable to grout fines and the inner surface ofth e sleeve being essentially g rout-permeable.

2. A method according to claim 1 wherein grout bags are secured together by heavy duty zips.

3. A method according to claim 1 wherein the lifting bag is filled with grout.

4. A method according to claim 1 wherein the or each grout bag is compartmentalised by internal walls allowing substantially free grout movement therethrough.

5. A method according to claim 1 wherein the grout impermeable sleeve walls are firmly woven fabric polyesteryarn.

6. A method according to claim wherein the polyesterfabric has a minimum weight of 200 g/m2, a tensile strength of at least 1500 n/cm2 in both warp and weft directions with an elongation of 15% and a water permeability of about 15 I/m2s under a 10 cm head.

7. A method according to claim 1 wherein the grout-permeable sleeve walls are open mesh fabric of polyamide yarn.

8. A method according to claim 7 wherein the polyamidefabric has a minimum weight of 11 g/m2, a tensile strength of at least 800 n/m2 in both warp and weft directions with an elongation of 25%.

9. A method of forming a circumferential grout coating around a length of recumbent pipe in situ, substantially as hereinbefore described with refer ence to the drawing.

10. A lifting grout bag substantially as hereinbefore described with reference to the drawing for use in a method according to claim 1.

11. A sleeving grout bag substantially as hereinbefore described with reference to the drawing for use in a method according to claim 1.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. around pipe2 is secured to an end ofthe illustrated bag,there may be groutflowthrough the abutting or adjacent internal walls ofthetwo bags. Instead ofthe arrangement shown, the lifting bag 8, or a series of such bags, may extend the full length ofthe pipe to be coated, or lifting bags 8 may be spaced longitudinally along the pipe. The grout-permeable wall 14 of bag 10may for example be an open mesh fabric of polyamide yarn; it will usually have a minimum weight of 110 gms. per sq. metre and preferably has a tensile strength of at least 800 N/Sc. in both warp and weft direction with an elongation of 25%.The outerwall 11 of bag 10 (and also the wall of lifting bag 8) should preferably have a water permeability of about 15 litres persq. metre per second under a 10cm. head, but be substantially impermeableto groutfines; it may for example be of firmly woven polyester yarn with a minimum weight of 200 gms. per sq. metre; its tensile strength is preferably at least 1500 N/5 cms. in both warp and weft directions with an elongation of 15%. The present invention resides not only in the indicated method of group coating, but also in the securable (e.g. byzipping) lifting and mainjacketing grout bags which are employed in performing the method. Whilst the method has been described forthe application of a grout coating to a sea-bed pipeline, it is similarly applicable to pipes on land. the grout employed may be a simple sand/cement blend, or one containing ballast or (especiallyforweight coatings) one containing barytes orthe like. CLAIMS (Filed on 18th October 1983)

1. A method offorming a circumferential grout coating around a length of recumbent pipe in situ by disposing a lifting grout bag underthe said length of pipe, completing a sleeve around the said length of pipe by covering its remaining circumferential surface with at least one further grout bag and securing together the juxtaposed edges of adjacent grout bag walls which form the outer circumferential surface of the sleeve, filling the lifting grout bag with fluid to lift the said length of pipe to a desired ground clearance, filling the grout bags with grout, and allowing the groutto set, the said grout bag walls forming the outer surface ofthe sleeve being permeable to water but substantially impermeable to grout fines and the inner surface ofth e sleeve being essentially g rout-permeable.

2. A method according to claim 1 wherein grout bags are secured together by heavy duty zips.

3. A method according to claim 1 wherein the lifting bag is filled with grout.

4. A method according to claim 1 wherein the or each grout bag is compartmentalised by internal walls allowing substantially free grout movement therethrough.

5. A method according to claim 1 wherein the grout impermeable sleeve walls are firmly woven fabric polyesteryarn.

6. A method according to claim wherein the polyesterfabric has a minimum weight of 200 g/m2, a tensile strength of at least 1500 n/cm2 in both warp and weft directions with an elongation of 15% and a water permeability of about 15 I/m2s under a 10 cm head.

7. A method according to claim 1 wherein the grout-permeable sleeve walls are open mesh fabric of polyamide yarn.

8. A method according to claim 7 wherein the polyamidefabric has a minimum weight of 11 g/m2, a tensile strength of at least 800 n/m2 in both warp and weft directions with an elongation of 25%.

9. A method of forming a circumferential grout coating around a length of recumbent pipe in situ, substantially as hereinbefore described with refer ence to the drawing.

10. A lifting grout bag substantially as hereinbefore described with reference to the drawing for use in a method according to claim 1.

11. A sleeving grout bag substantially as hereinbefore described with reference to the drawing for use in a method according to claim 1.