GB1598822A

GB1598822A - Pipe protection

Info

Publication number: GB1598822A
Application number: GB481977A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-04
Filing date: 1978-05-04
Publication date: 1981-09-23

Description

(54) PIPE PROTECTION (71) We, KEITH WHITTAKER and JAMES EDWARD DOYLE, both British subjects of 2 James Avenue, Eastburn, Near Keighley, Yorkshire, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the protection of pipes from internal abrasion.

Pipes used to convey fluent material containing solid particles may suffer serious wear at their inner surfaces because of the abrasive action of the particles. This is a problem in the cases for example of pipes conveying slurries of sand, mining residues, ash and like materials.

An objection of the present invention is to provide a means of protection for pipes whereby the problem of abrasive wear at their inner surfaces may be avoided or at least appreciably reduced.

According to the invention there is provided a method of protecting the inner surface of a pipe from abrasion by fluent materials passing through the pipe which comprises installing within the pipe a preformed tube of polymeric material having a greater abrasion resistance than said pipe and having at least one portion having a greater wall thickness than that of at least one other portion, so as to provide a protective barrier in use between said inner surface and said fluent material, and anchoring said pre-formed tube in said pipe at one or a plurality of discrete locations.

Preferably the polymeric material is an elastomer particularly polyurethane elastomer and the tube is formed by extrusion, moulding or other means. Whilst the tube is formed prior to installation in the pipe, final curing of the polymeric material by thermal or chemical means may be completed within the pipe. Also, whilst the tube may be pre-formed so as to have a cross-sectional shape corresponding to the shape of the inner surface of the pipe, this is not necessarily the case and the tube may be initially in a collapsed state or in a shape not conforming to the pipe inner surface the requisite shape being adopted by the tube during installation.

The wall thickness of the polymeric tube, which need not be the same for all positions along the length of the pipe, may be selected in accordance with the severity of the abrasive nature of the moving material, any increase in pumping costs caused by reduction of the cross-sectional area of the pipe available for fluid flow by the introduction of the tube, the strength of the tube required to ensure that excessive longitudinal strain of the lining does not occur in use such as to cause buckling, and the choice of polymeric materials available for a particular application which may depend upon cost factors and chemical compatibility with the moving material. For most applications the wall thickness of the tube may fall within the range of 3mm to 15mm; however the wall thickness need not be uniform around the tube. For instance it may be desirable for reasons of cost to line a pipe bend with a polymeric tube of non-uniform wall thickness such that the lining thickness becomes progressively greater as the distance from the centre of curvature of the bend increases, so that greatest protection is afforded where the tube is likely to be subjected to greatest abrasive wear. The tube may be strengthened by incorporation of strengthening material in the polymeric material particularly fibrous strengthening materials of a woven or non-woven form such as canvas, glass fibre or the like. With such strengthening materials, the wall thickness of the tube can be kept to a minimum whilst maintaining adequate strength.

The protective tube may be introduced into the pipe and anchored therein in any suitable manner. Thus, for example, the tube may be drawn into the pipe by winch and cable. The outside diameter of the tube may be substantially the same as the inside diameter of the pipe, and a tight fit in this respect may be achieved by expanding the tube by pressure or mechanical means after insertion. The tube may be anchored by being frictionally held in the pipe due to a tight fit, or by a bonding technique, or by mechanical clamping, or by a combination of such means. The anchorage of the tube need not be effected in continuous manner along the entire length of the tube, but may be effected only at selected locations along the length thereof, for example at a conveniently accessible position in the pipe particularly at or near an upstream end or both ends of the pipe. It will be appreciated that the anchorage of the tube within the pipe does not necessarily make the tube an inseparable part of the pipe and that a worn protective tube may be replaced with a new protective tube without renewal of the pipe itself.

Also, it will be appreciated that the invention is applicable not only to new pipes but also to ones which may have been used for some time, and additionally that a worn protective tube may itself be protected by introduction of a further protective tube inside it as if the worn tube were the pipe wall when this is preferable to removing and replacing the worn tube.

It is visualised that the invention will have particular application to the protection of steel pipe but the invention is not intended to be restricted thereto and may be applied to rigid or flexible pipe or ducting of circular or non-circular cross-section of any material used for conveying abrasive materials or for any other suitable purpose.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic elevation of a pipe installation; Figure 2 is a diagrammatic plan view of the arrangement of Figure 1; Figure 3 is a diagrammatic longitudinal section of a pipe bend of the installation of Figures 1 and 2 during installation of a lining tube therein; and Figure 4 is a cross-section of the lining tube of Figure 3.

The pipe installation of Figures 1 and 2 is for conveying a fluent, abrasive mineral residue slurry along a steel pipeline 1 from a pumphouse 2 to a spoil dump 3. Obstruc tions 4 and 5 in the path of the pipeline 1 necessitate bends 6 and an underground section 7.

In order to protect against abrasive wear of the pipe walls and to remedy any wear which has already occurred as indicated for example by leakage at the bends 6 where wear is greatest, the pipe is lined with a polyurethane elastomer tube of hardness 90 Shore A and a wall thickness of 6 mm throughout most of its length. The tube wall thickness may reduce to 5 mm along a high section 8 of the pipeline where less strength is required to resist longitudinal stress produced by the combination of pump 'shut-off' pressure and static head e.g. in the event of a blockage. A greater wall thickness, as described in more detail later, may be utilised at the bends where greatest wear is experienced.

In order to effect lining of the pipeline, the bends are removed and sections approximately 6m in length are cut from the pipe at positions 9 and 10 to provide access. The greatest distance between excised sections is determined, in the absence of overriding determination by tube strength limitations, by the continuous length of tube which can conveniently be made available. In this respect, the tube may be wound onto a large drum fabricated for this process of like form to but larger than the drums commonly used for electric cables. The upper limit may be, for example, lkm. Flanges are welded onto the pipe ends at the breaks thus formed, except where it is possible to utilise an existing flanged joint in making the excisions, so that the parts removed may be replaced easily after lining of the pipe has been effected.

After insertion of the tube into the pipe, in the manner yet to be described, adhesive bonding is used for anchorage of the protective tube within the pipe, and in so far as the simplicity of the pipe installation shown is such as to make reverse flow extremely unlikely, only upstream ends of the tube need be anchored.

The same bonding technique is used for both the long sections of pipe and the short excised sections. The first 50cm of the pipe interior at the upstream end is carefully cleaned and primed with a suitable bonding agent prior to introduction of the tube.

When the tube is in place adhesive is introduced between the pipe and the tube by injection through a hollow needle inserted between the pipe wall and the outer surface of the tube to a distance of approximately 50cm from the open end and slowly withdrawn whilst the adhesive is being forced through the needle under pressure.

The needle is withdrawn so as to trace a helix with its discharge end in order to ensure uniform spread of adhesive between the pipe and the tube. If a tube of greater wall thickness is to be used, this technique becomes more difficult and multiple axially parallel insertions of the needle may be preferable to ensure good adhesive spread.

The adhesive used is of a catalyst-activated cold-curing type and after sufficient time has elapsed for curing to take place any surplus tube projecting from the pipe end is cut off.

Because of the high integrity of bonding required particular care is exercised in the use of the adhesive, particularly in ensuring intimate mixing of the catalyst with the base prior to injection and in the observance of manufacturers data on pot life and curing time which are strongly affected by working temperatures.

The lining tube is drawn into the pipe by a winch cable securely clamped to the end of the lining tube, the cable having first been fed through the pipe by one of several well-known methods utilising for example a draw rod, ferret or electric tug. Preferably the outer diameter of the tube is selected so that the tube fits closely within the pipe but can slide easily into the pipe in so far as lubrication or contamination by grease of the surfaces to be bonded necessitates trou blesome solvent cleaning procedures. Any burrs or similar imperfectlons at the open end of the pipe which might interfere with the smooth passage of the lining tube are removed prior to introduction of the tube.

The pipe bends, after patching or replace ment where necessary, are lined with a partly-cured polyurethane tube which is in a softer state, of about 45 Shore A hardness, than the fully-cured tube used to line the straight pipe sections. After introduction of the adhesive this softer tube is cured by steam heating under internal pressure to ensure a good fit within the bend. As shown in Figure 3, steam at approximately 2 bar.g is fed via valve 11 into the lining section 12 which is closed by bungs 13, 14 close to end flanges 15 of the pipe bend, the bungs being gripped in the tube by Jubilee clips 16 or similar detachable devices around the tube.

A steam trap 17 is provided for draining condensed steam and a vacuum release device 18 is provided to prevent collapse of the lining on cut-off of steam. A pressure gauge 19 is also provided. Curing takes approximately 1 to 3 hours depending on the temperature involved and the particular type and initial hardness of the elastomer, and a complete cure may be ensured by testing the tube hardness with a hand-held hardness meter.

As shown in Figure 4, the tube 12 used to line the pipe bends may be of non-uniform wall thickness and may have a small projec tion 20 to facilitate positioning of the thick est part of the lining at the outside of the bend.

When the lining operations have been completed, the excised parts are refitted into the pipeline utilising the flanges for fixing purposes. care being taken to ensure that an adhesive anchorage is located at the upstream end of each component.

With the embodiment described above, it may be convenient to draw the lining tube beyond the end of the steel pipe (21 in Figures 1 and 2) and slide over it one or more additional pipe sections to follow advance of the spoil dump. Further lines or unlined sections may be added to follow further advance in the future, and new intermediate sections may be introduced in the future at any point provided that due care is taken to provide suitable anchorage of the lining at any end of a piping section which can be an upstream end having regard to possible normal and abnormal flow conditions.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

WHAT WE CLAIM IS: 1. A method of protecting the inner surface of a pipe from abrasion by fluent materials passing through the pipe which comprises installing within the pipe a preformed tube of polymeric material having a greater abrasion resistance than said pipe and having at least one portion having a greater wall thickness than that of at least one other portion, so as to provide a protective barrier in use between said inner surface and said fluent material, and anchoring said pre-formed tube in said pipe at one or a plurality of discrete locations.

2. A method according to claim 1 wherein the polymeric material is an elastomer.

3. A method according to claim 2 wherein the elastomer is polyurethane.

4. A method according to any one of claims 1 to 3 wherein the tube is pre-formed so as to have a cross-sectional shape corresponding to the shape of the inner surface of the pipe.

5. A method according to any one of claims 1 to 3 wherein the tube is constrained to adopt a shape conforming to the shape of the pipe inner surface on installation of the tube.

6. A method according to any one of claims 1 to 5, wherein the tube is cured when fitted within the pipe.

7. A method according to any one of claims 1 to 5, wherein the tube is of a wall thickness 3mm to 15mm.

8. A method according to any one of claims 1 to 7 wherein different lengths of the tube have different wall thicknesses.

9. A method according to any one of claims 1 to 8 wherein different portions of the tube around the circumference thereof have different wall thicknesses.

10. A method according to any one of claims 1 to 9 wherein the polymeric material

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. preferable to ensure good adhesive spread. The adhesive used is of a catalyst-activated cold-curing type and after sufficient time has elapsed for curing to take place any surplus tube projecting from the pipe end is cut off. Because of the high integrity of bonding required particular care is exercised in the use of the adhesive, particularly in ensuring intimate mixing of the catalyst with the base prior to injection and in the observance of manufacturers data on pot life and curing time which are strongly affected by working temperatures. The lining tube is drawn into the pipe by a winch cable securely clamped to the end of the lining tube, the cable having first been fed through the pipe by one of several well-known methods utilising for example a draw rod, ferret or electric tug. Preferably the outer diameter of the tube is selected so that the tube fits closely within the pipe but can slide easily into the pipe in so far as lubrication or contamination by grease of the surfaces to be bonded necessitates trou blesome solvent cleaning procedures. Any burrs or similar imperfectlons at the open end of the pipe which might interfere with the smooth passage of the lining tube are removed prior to introduction of the tube. The pipe bends, after patching or replace ment where necessary, are lined with a partly-cured polyurethane tube which is in a softer state, of about 45 Shore A hardness, than the fully-cured tube used to line the straight pipe sections. After introduction of the adhesive this softer tube is cured by steam heating under internal pressure to ensure a good fit within the bend. As shown in Figure 3, steam at approximately 2 bar.g is fed via valve 11 into the lining section 12 which is closed by bungs 13, 14 close to end flanges 15 of the pipe bend, the bungs being gripped in the tube by Jubilee clips 16 or similar detachable devices around the tube. A steam trap 17 is provided for draining condensed steam and a vacuum release device 18 is provided to prevent collapse of the lining on cut-off of steam. A pressure gauge 19 is also provided. Curing takes approximately 1 to 3 hours depending on the temperature involved and the particular type and initial hardness of the elastomer, and a complete cure may be ensured by testing the tube hardness with a hand-held hardness meter. As shown in Figure 4, the tube 12 used to line the pipe bends may be of non-uniform wall thickness and may have a small projec tion 20 to facilitate positioning of the thick est part of the lining at the outside of the bend. When the lining operations have been completed, the excised parts are refitted into the pipeline utilising the flanges for fixing purposes. care being taken to ensure that an adhesive anchorage is located at the upstream end of each component. With the embodiment described above, it may be convenient to draw the lining tube beyond the end of the steel pipe (21 in Figures 1 and 2) and slide over it one or more additional pipe sections to follow advance of the spoil dump. Further lines or unlined sections may be added to follow further advance in the future, and new intermediate sections may be introduced in the future at any point provided that due care is taken to provide suitable anchorage of the lining at any end of a piping section which can be an upstream end having regard to possible normal and abnormal flow conditions. It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only. WHAT WE CLAIM IS:

1. A method of protecting the inner surface of a pipe from abrasion by fluent materials passing through the pipe which comprises installing within the pipe a preformed tube of polymeric material having a greater abrasion resistance than said pipe and having at least one portion having a greater wall thickness than that of at least one other portion, so as to provide a protective barrier in use between said inner surface and said fluent material, and anchoring said pre-formed tube in said pipe at one or a plurality of discrete locations.

3. A method according to claim 2 wherein the elastomer is polyurethane.

incorporates a strengthening material.

11. A method according to any one of claims 1 to 10 wherein the pre-formed tube is drawn into the pipe and forms a tight fit against the inner surface of same.

12. A method according to any one of claims 1 to 11 wherein the tube is anchored within the pipe by anchoring means.

13. A method according to claim 12 wherein said anchoring means comprises adhesive means.

14. A method according to claim 12 or 13 wherein said anchoring means is applied to the tube only in the vicinity of an end thereof.

15. A method according to claim 14 wherein said anchoring means is applied at an upstream end with respect to the direction of movement of conveyed material.

16. A method according to claim 1 substantially as hereinbefore described.

17. A pipe when protected in accordance with the method of any one of claims 1 to 16.