SPECIFICATIONMethod of and apparatus for lining a hollow memberThis invention relates generally to the lining of a hollow member and is particularly concerned with the lining of tubular members such as pipes.
Steel pipes are widely used, in many applications, because of their inherent strength.
Steel is however not suitably corrosion resistant to certain materials and consequently steel pipes must be lined, for certain uses, to achieve satisfactory performance. For example a steel pipe may be lined with lead to provide a composite pipe of desired characteristics.
One technique known to the applicant is simply to insert a tubular preformed lead liner into a steel pipe. This type of construction does offer suitable anti-corrosion properties but it has certain drawbacks. For example if the interior of the pipe is subjected to vacuum then the lead liner can be buckled inwardly by the pressure exerted on the exterior of the liner by the air between the outer surface of the liner and the inner surface of the pipe.
Another drawback is that as the lead and steel are not in intimate contact the heat transfer capability of the composite pipe, from inside to outside or from outside to inside as the case may be, is not efficient.
It is an object of the present invention to provide a method of lining the interior of a hollow member. Although the method is particularly suited for lining the interior of a pipe it does however find application in other areas and consequently the scope of this specification is not to be restricted to pipe lining.
The invention provides a method of lining the interior of a hollow member which includes the steps of locating a preformed liner inside the hollow member, and expanding the liner into contact with the inner wall of the tubular member.
The liner may be expanded by means of a pressurised fluid located inside the liner. The fluid may be pressurised in any suitable way for example with the aid of pumps or the like.
The fluid may be gaseous or liquid.
According to a variation of the invention the liner is expanded by force generated through the combustion, ignition or detonation of a combustible or explosive material. For example use may be made of an explosive charge which is positioned in the interior of the liner and then detonated. In a preferred form of the invention use is made of an explosive gaseous mixture for example a mixture of hydrogen and oxygen which is caused to ignite or combust inside the liner under sealed conditions.
The method may include the step of locating an adhesive material between the inner surface of the hollow member and the outer surface of the liner. The adhesive intimately bonds these two surfaces together once the liner has been expanded.
The principles of the invention may be used with any suitable shape of tubular member but find particular application to the lining of a pipe. In this event the liner is preformed as a pipe with an outer diameter slightly less than the inner diameter of the pipe. The pipe itself may be made from any suitable material for example steel. The liner, for all applications, is also made of a suitable material for example as elastic or malleable material. The liner may be made from lead or from a lead alloy.
The invention is also intended to cover a pipe lined in accordance with the aforementioned method.
The invention further extends to a composite pipe which includes an outer pipe, an inner pipe, which is located inside the outer pipe, and adhesive means intimately bonding the outer surface of the inner pipe to the inner surface of the outer pipe.
The adhesive used may itself be heat conductive so that, according to the application, the composite pipe is highly heat conductive.
The invention is further described by way of example with reference to the accompanying drawings in which:Figure 1 illustrates in radial cross-section a pipe which is being lined in accordance with the principles of the invention, andFigure 2 shows the pipe of Fig. 1 in axial cross-section.
The drawings illustrate an outer steel pipe 10 which has an inner liner 12 of lead or lead alloy. Adhesive 14 covers the inner surface of the steel pipe and the outer surface of the lead liner.
In the construction of the composite pipe the outer steel pipe 10 is preformed and so is the inner lead liner 12. The liner and the inner surface of the pipe 10 are degreased. The lead liner has an outside diameter which is slightly less than the inner diameter of the steel pipe. The adhesive material 14, which is initially fluent, is applied to the inner surface of the steel pipe, or to the outer surface of the lead liner, or to both these surfaces.
Thereafter the liner is positioned inside the steel pipe.
Both ends of the liner are sealed off by means of plates 16 which are fixed to flanges on the pipe 10 to provide a gas tight enclosure. The interior of the liner is then purged of air and is filled by a mixture 18 of hydrogen and oxygen which is supplied from a source 20 through a suitable valve 22 which is mounted in a pipeline which extends through one of the plates 16. The hydrogen/oxygen mixture 18, which is explosive, is then ignited by means of a spark which is induced across two electrodes 24 which extend into the mixture, from the other plate 16. The electrodes 24 are conveniently provided by a suitable spark plug. The lead liner is thereby subjected to substantial radially outwardly directed pressure, indicated by arrows 26, and so is expanded outwardly into intimate contact with the inner wall of the steel pipe. The adhesive 14 then bonds the two components to one another.
The adhesive 14, which is fluent, assists in the expulsion of air from the lead/steel interface. Secondly the adhesive ensures that the lead liner remains bonded to the steel pipe even if the interior of the liner is subjected to vacuum pressure. A third aspect is that the adhesive may itself be made from a heat conductive material and this ensures a high efficiency of heat transfer from the interior of the liner to the exterior of the steel pipe, or in the reverse direction if required. The adhesive can be of any suitable kind and one which has been found to give satisfactory performance is that sold under the trade name MIDBOND byParagon Rubber.
The method of the invention can be used to line steel pipes over a wide range of diameters with a lead lining. The thickness of the lining can also be varied over a considerable range to suit the particular application. It has been found that pipes lined in accordance with the invention are able to withstand a full vacuum at temperatures of up to 150 C.
The invention has been described with reference to the use of an explosive mixture which expands the liner. As indicated an explosive charge could also be used to generate the desired expansive forces. Another possibility is to use a pressurized fluid which is pumped into the interior of the sealed liner and maintained under pressure by means of high pressure pumps. The arrangement, in this application, is similar to that shown in Fig. 2 where the reference 20 designates a high pressure pump. Obviously the electrodes 24 would not be required.