GB2455675A

GB2455675A - Metal pipe with lining and its manufacturing method

Info

Publication number: GB2455675A
Application number: GB0906145A
Authority: GB
Inventors: Ruquan Mo
Original assignee: GUANGDONG SUCCESSFUL MAN PIPE
Current assignee: GUANGDONG SUCCESSFUL MAN PIPE
Priority date: 2006-09-08
Filing date: 2007-08-31
Publication date: 2009-06-24
Anticipated expiration: 2027-08-31
Also published as: AU2007306853A1; GB2455675B; GB0906145D0; NZ576166A; RU2009113170A; CN200946722Y; WO2008043237A1

Abstract

A metal pipe with a plastic lining includes a metal pipe (1), the inner wall of said pipe (1) lined with a first protecting layer (2) and the outer wall covered by a second protecting layer (3). Said first protecting layer (2) is made from polyethylene or polypropylene material, and the second protecting layer (3) is made from polyvinyl chloride film. Accordingly, a method for making the pipe includes the following steps: a. preparing the metal blank pipe used for the metal pipe (1) and the plastic blank pipe used for the first protecting layer (2); b. putting the plastic blank pipe into the metal blank pipe and stretching forcibly the metalblank pipe to reduce the radial dimension to make it excessively fit with the plastic pipe blank; c. conducting repeated ageing to the stretched metal blank pipe and plastic blank pipe at given temperature to eliminate the processing stress and the remained inner stress of the material.

Description

METAL PIPE WITH PLASTIC LINING AND ITS MANUFACTURING METHOD

Field of Invention

The present invention relates to a metal pipe with a plastic lining and its manufacturing method, said metal pipe is particularly related to a metal pipe applicable to clean water conveying systems, building water supply systems and fluid conveyance in food, pharmaceutical and winery industries and so on.

Background

Typically, clean water conveying systems, building water supply systems and fluid conveyance in the food, phannaceutical and winery industries usually adopt pipes to convey fluid. Without corresponding protective equipment, conventional conveyance pipes may be oxidized during usage and become rusted. As a result, this type of pipe has a limited durability and does not guarantee the quality of fluid conveyed via the pipe.

In the prior art, plastic pipes have been adopted as examples to convey fluid in situations where high quality fluid conveyance is not essential. Obviously, it is hard to guarantee the fluid conveyance quality using such pipes, mainly for the reason that the pipe material is not strong enough.

One current technique available in the industry involves combining a steel pipe and a plastic pipe in a variety of ways, often requiring adhesive glue, and the anti-rusting objective is achieved by providing a protective plastic pipe inside the steel pipe. However, with the limited technology at present, during practical application, the plastic pipe may come loose or move in this type of conveyance pipe thus giving the plastic pipe a short durability. Therefore, this type of conveyance pipe cannot provide effective anti-rusting properties and sometimes it may make the problem worse.

Summary of Invention

One objective of the invention is to overcome the above-mentioned shortcomings by providing a metal pipe with plastic lining and its manufacturing method, so as to effectively prevent contaminating fluid with a rusted metal pipe when a metal pipe is being used.

The objective of the invention is achieved through the following technical schemes: The metal pipe with plastic lining according to the present invention, applicable to fluid conveyance, includes a metal pipe, the inner wall of said metal pipe (1) is lined with a first protective layer (2), and the outer wall of the metal pipe is covered with a second protective layer (3).

Said first protective layer (2) is made from polyethylene or polypropylene material, and satisfies the non-toxic food grade hygiene standard.

Said second protective layer (3) is made from polyvinyl chloride film.

Said metal pipe is made from aluminum pipe and is a seamless pipe.

The manufacturing method of the metal pipe with plastic lining according to the present invention includes the steps of: a. Preparing a metal blank pipe that serves as the metal pipe and a plastic inner blank pipe that serves as the first protective layer; b. Disposing said plastic inner blank pipe inside said metal blank pipe, stretching the metal blank pipe forcibly in such a way that its radial dimension is reduced to form an interference fit with the plastic inner blank pipe; c. Subjecting the metal blank pipe and the plastic inner blank pipe, after the stretching and the forming of a composite, to a repetitive aging treatment at a specific temperature, so as to remove the processing stress and residual inner stress of the material.

The specific temperature at which the aging treatment is carried out in step c is about -20 °C -100°C.

The outer diameter of said plastic inner blank pipe is 2mm to 3mm smaller than inner diameter of said metal pipe in step a.

Preferably, said metal blank pipe is made from aluminum, said plastic inner blank pipe is made from polyethylene or polypropylene.

In addition, step d: covering the outer wall of the metal blank pipe with a plastic film made from polyvinyl chloride that serves as the second protective layer, and covering the outer wall of said metal blank pipe by the same technique in steps a, b and c, is also included.

In comparison with the current technology, the present invention has the following advantages: by lining the inner wall of metal pipe with a first protective layer of non-toxic food grade, the benefits of metal and plastic may be combined together to ensure that plastic inner blank pipe keeps the inner layer of the pipe clean, hygienic, non-clogging and non-rusty, and at the same time separate the metal blank pipe from the fluid to prevent contaminating the fluid with the rusted residues produced from the metal pipe. Meanwhile, the metal pipe provides higher mechanical strength for the pipe, and the second protective layer that covers the outer surface of the pipe, provides better protection for the pipe during practical application and construction.

Description of Attached Drawings

Figure 1 illustrates a longitudinal section of the metal pipe with a plastic lining according to the present invention; Figure 2 illustrates a cross section of the metal pipe with plastic lining according to the present invention.

Detailed Descriptions of the Embodiments

The present invention is described in details with the attached drawings and the embodiments below.

Referring to Figures 1 and 2, the present invention differs from the prior art in that the metal pipe with plastic lining is a triple-layered structure which specifically includes a metal pipe 1, a first protective layer 2 and a second protective layer 3.

The metal pipe 1 mainly enhances mechanical strength for the pipe, and may be made from a variety of alloys which satisfy strength requirements in the specific situations. The alloys may be selected from common materials such as steel, aluminum, iron and so on. In the present embodiment, the aluminum alloy material is chosen for its light weight, durability and anti-rusting property. Therefore, aluminum alloy offers a more practical choice than steel or iron.

The first protective layer 2 is made from plastic materials, specifically from polyethylene or polypropylene. In order to accommodate specific situations, polyethylene or polypropylene preferably satisfies the non-toxic food grade requirement. The first protective layer 2 forms a tight composite with said metal pipe 1 as a plastic lining, without adding any adhesive, to provide strong protection for the metal pipe 1 made from aluminum. The thickness of the first protective layer 2 may be variable. The inner diameter of the first protective layer 2 is determined by the required cross-sectional area of the fluid conveyed by the pipe. Preferably, the outer diameter of the first protective layer 2 is 2mm to 3 mm smaller than the inner diameter of the metal pipe 1 in order for the outer diameter of the first protective layer 2 to match with the inner diameter of the metal pipe 1.

By the same principle, the second protective layer 3 is also made from plastic materials, specifically from polyvinyl chloride to form a tight composite with the outer wall of the metal pipe 1, so that the outer wall of the metal pipe 1 is protected from rusting.

The method of manufacturing said plastic lining is specifically embodied in the triple structure.

The present invention differs from the prior art in that a cold drawing method is adopted to result in a radial deformation to the blank pipe shape of the metal pipe 1, such that the plastic inner pipe is tightly sleeved with the metal pipe and said inner pipe forms the first protective layer 2.

Specifically, the following methods may be adopted to combine both the first protective layer 2 and second protective layer 3 to the metal pipe 1.

First of all, the metal blank pipe that serves as the metal pipe I may be prepared according to the defined dimension. In this case, the metal blank pipe that is aluminum blank pipe and the polyethylene or polypropylene plastic inner blank pipe that serves as the first protective layer 2 may be prepared. The plastic inner blank pipe is fitted in the aluminum blank pipe. The outer diameter of said plastic inner blank pipe is 2 to 3 mm smaller than inner diameter of said aluminum blank pipe, so as to accommodate the matching with each other during the subsequent processing.

Next, the aluminum blank pipe is forcibly stretched via the mould using the stretching machine to reduce its radial dimension so as to form an interference fit with said plastic inner blank pipe.

As a result, a certain degree of combination is achieved between aluminum blank pipe and the plastic inner blank pipe and will not fall apart, and a stable composite is achieved without adding any adhesive glue.

Lastly, a repetitive aging treatment at -20 °C -100 °C is performed after the aluminum blank pipe and plastic inner blank pipe are stretched to form a composite, so as to remove the processing stress and residual inner stress of the material. This ensures that linear expansion system of plastic approaches that of aluminum alloy, so as to ensure no occurrence of laminar peeling and contracting at normal temperature range (20 °C to 80 °C).

Once the first protective layer 2 forms a tight composite with said metal pipe I, the polyvinyl chloride outer blank pipe that serves as the second protective layer 3 may form a composite with said metal pipe 1 by the above-described method, so as to form the metal pipe with plastic lining according to the present invention.

It is necessary to further emphasize that the first protective layer 2 and second protective layer 3 are not limited to material described in the present embodiments. That is, said second protective layer 3 may also be made from polyethylene or polypropylene.

The metal pipe with plastic lining of the invention may be widely applicable to clean water conveying systems, building water supply systems, and fluid conveyance in the food, pharmaceutical and winery industries and so on. It may also be used to convey fuel gas in the fuel system with reliability and safety.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

I. A metal pipe with plastic lining, applicable to the conveying of fluid, comprises a metal blank pipe and is characterized in that: an inner wall of said metal blank pipe (1) is lined with a first protective layer (2), an outer wall of the metal blank pipe is covered with a second protective layer (3).
2. The metal pipe with plastic lining according to claim 1 is characterized in that: said first protective layer (2)is made from polyethylene or polypropylene.
3. The metal pipe with plastic lining according to claim 1 or 2 is characterized in that: said second protective layer (3) is made from polyvinyl chloride.
4. The metal pipe with plastic lining according to claim I or 2 is characterized in that: said metal pipe is made from aluminum and is a seamless blank pipe.
5. The metal pipe with plastic lining according to claim 3 is characterized in that: said metal pipe is made from aluminum and is a seamless blank pipe.
6. A method for manufacturing metal pipe with plastic lining is characterized in that it comprises steps of: a. preparing a metal blank pipe that serves as the metal pipe (I) and a plastic inner blank pipe (2) that serves as the first protective layer; b. disposing said plastic inner blank pipe inside said metal blank pipe, forcibly stretching the metal blank pipe in such a way that its radial dimension is reduced to form an interference fit with the plastic inner blank pipe; c. subjecting the metal blank pipe and the plastic inner blank pipe, after its stretching and the forming of a composite, to a repetitive aging treatment at a specific temperature, so as to remove material processing stress and residual inner stress.
7. The method for manufacturing the metal pipe with plastic lining according to claim 6 is characterized in that the specific temperature at which the aging treatment is carried out in step c is about-20-. 100°C.
8. The method for manufacturing the metal pipe with plastic lining according to claim 6 is characterized in that the outer diameter of said plastic inner blank pipe is 2 to 3 mm smaller than inner diameter of said metal pipe in step a.
9. The method for manufacturing the metal pipe with plastic lining according to any one claim of claims 6 to 8 is characterized in that: said metal blank pipe is made from aluminum, said plastic inner blank pipe is made from polyethylene or polypropylene.
10. The manufacturing method for the metal pipe with plastic lining according to claim 9 is characterized by further comprising step d: covering the outer wall of the metal blank pipe with a

I

plastic film made from polyvinyl chloride that serves as the second protective layer (2), and covering the outer wall of said metal blank pipe with the same technique as in steps a, b and c.