GB2296303A

GB2296303A - Plastics piping

Info

Publication number: GB2296303A
Application number: GB9519031A
Authority: GB
Inventors: John Stafford Rowland
Original assignee: Extrudit Ltd
Current assignee: Extrudit Ltd
Priority date: 1994-12-22
Filing date: 1995-09-18
Publication date: 1996-06-26
Anticipated expiration: 2015-09-18
Also published as: GB9425902D0; GB9519031D0; GB2296303B

Abstract

Plastic piping (1), is formed as a multi-layer, tubular extrusion comprising an external layer (2) of white coloured plastics, and at least one internal layer (3, 5) of dark coloured plastics that is effective as a light barrier. An oxygen barrier layer (4) may also be provided. <IMAGE>

Description

PLASTICS PIPING This invention relates to plastics piping for the conveyance of water.

Plastics piping has in principle been used previously not only for central heating, but also for hot and cold water systems. However, in order to guard against the build-up of algae in water piping, particularly potable water piping, due to the effect of light permeability through plastics, previous systems have had to be produced in dark coloured plastics, typically in polybutalene which, being grey or brown in colour, and whilst having the desired technical effect, is aesthetically unattractive, particularly to domestic users and/or requires painting in the user-preferred colour - white.

As an alternative to the inherent domestic customerresistance to the purchase and installation of grey or brown tubing, an alternative but more expensive strategy is for suppliers or stockists of systems to carry two distinct types of tubing, viz. white plastics tubing for central heating and for hot and cold water systems, and copper tubing for potable water systems. Apart from copper tubing more expensive than plastics tubing, copper has a residual value and hence is a target for theft from the premises of suppliers or stockists.

Furthermore, care is required to ensure that the correct quantities of both types of tubing are estimated and delivered to an installation site.

A basic object of the present invention is to provide plastic piping in the most widely demanded colour, white, which is suitable for most, if not all, water systems.

According to the present invention, there is provided plastic piping, being a multi-layer, tubular extrusion comprising an external layer of white coloured plastics, and at least one internal layer of dark coloured plastics that is effective as a light barrier.

The dark coloured plastics may be in grey, black, blue or brown to create the light barrier, ideally to prevent the penetration of no more than 0.2% of light into the tubing, thus enabling white externally coloured tubing to pass the necessary WRC testing regulation to obtain a potable drinking water certificate, in accordance with BS 2782 Part II Method 1104A or indeed a future update test requirement.

Experimentation with dark pigments and wall thickness will ensure exclusion of light to meet WRL regulations.

Similar experimentation with differing plastics materials, wall thicknesses, and numbers of layers will ensure that the piping is also suitable for central heating up to BS 7291 Class S hot and cold domestic water systems.

In accordance with a further feature of the invention, plastics piping for central heating systems additionally incorporates an extruded, oxygen barrier layer intermediate the external and internal layers, to assist in prevention of erosion. In addition, a first tie layer may interconnect the internal periphery of the external layer to the external periphery of the oxygen barrier layer, and a second tie layer may interconnect the internal periphery of the oxygen barrier layer to the external periphery of the internal layer, so that this tubing is a five layer extrusion.

Thus, the plastics piping in accordance with the various aspects of the invention is readily capable of carrying water at mains pressure, and achieves not only a user-attractive appearance by the external layer being white, but also provides the stockists, distributors and installers with the fundamental advantage that one and the same tubing may be used for most water systems, due to the presence of the dark coloured light barrier layer, and all water systems if the tubing additionally incorporates the oxygen barrier layer thereby rendering the tubing additionally suitable for central heating systems. Furthermore, the tubing in accordance with the various aspects of the invention, is not only cheaper to produce than copper tubing but being all plastics has, unlike copper tubing, no re-sale value and hence is not a target for theft.Furthermore, being leadfree and non-toxic the piping in accordance with the invention will not support bacteriorlogical growth and will therefore meets water-industry standards.

The inner and outer layers may be of polyethylene, preferably high density cross-linked polyethylene (or similar material), which is resistant to abrasion, impact, puncturing, stress cracking and aging, and provides the inner layer with a smooth bore finish to ensure free flow and to avoid build-up of scale. Any oxygen barrier may be EVOH.

Typically, the outer layer is of 0.5 mm wall thickness and the inner layer of 1.45 mm thickness.

A section of piping in accordance with the invention and suitable for all water systems is shown by way of example in the accompanying drawing.

The drawing is, to an enlarged scale for purposes of illustration, a cross section through plastics piping 1, which is a five layer tubular extrusion comprising, from outside to inside, an external layer 2 of white coloured high density, cross-linked polyethylene, typically 0.5mm wall thickness, inside which is a first tie layer 3 to interconnect the internal periphery of the external layer 2 to the external periphery of an oxygen barrier layer 4, and a second tie layer 5, typically of 1.45mm wall thickness, to interconnect the internal periphery of the oxygen barrier layer to the external periphery of an internal layer 6.

The external layer 2 is white coloured plastics, while at least one of the layers 3, 4 and 5 is dark coloured plastics, whilst the internal layer 6 is of any convenient colour.

Claims

1. Plastic piping, being a multi-layer, tubular extrusion comprising an external layer of white coloured plastics, and at least one internal layer of dark coloured plastics that is effective as a light barrier.

2. Piping as claimed in Claim 1, wherein the dark coloured plastics is grey, black, blue or brown.

3. Piping as claimed in Claim 1 or Claim 2, wherein the dark coloured plastics is such that it prevents no more than 0.2% of light penetration into the tubing.

4. Piping as claimed in any preceding claim, for central heating systems additionally incorporating an extruded, oxygen barrier layer intermediate the external and internal layers, to assist in prevention of erosion.

5. Piping as claimed in Claim 4, wherein a first tie layer interconnects the internal periphery of the external layer to the external periphery of the oxygen barrier layer, and a second tie layer interconnects the internal periphery of the oxygen barrier layer to the external periphery of the internal layer, so that this tubing is a five layer extrusion.

6. Piping as claimed in any preceding claim, wherein the inner and outer layers are of polyethylene, preferably high density cross-linked polyethylene ( or similar material ).

7. Piping as claimed in Claim 4 and any claim appendant thereto, wherein the oxygen barrier is EVOH

8. Piping as claimed in any preceding claim, wherein the outer layer is of 0.5mm wall thickness.

9. Piping as claimed in any preceding claim, wherein the inner layer is of 1.45mm thickness.

10. Plastics piping, substantially as hereinbefore described with reference to the accompanying drawing.

Amendments to the claims have been filed as follows CLAIMS

1. Potable water piping of plastics, being a twolayer, tubular extrusion, one layer being an outer tube of white coloured polyethylene, extruded around the external periphery of an inner tube of dark coloured polyethylene that is effective as a light barrier to preclude light penetration into the interior of the inner tube.

2. Piping as claimed in Claim 1, wherein the dark coloured, inner tube of polyethylene is grey, black, blue or brown.

3. Piping as claimed in Claim 1 or Claim 2, wherein the dark coloured, inner tube of polyethylene is such wall thickness and dark pigmentation that it prevents no more than 0.2% of light penetration into the interior of the inner tube.

4. Potable water and/or central heating plastics piping being an outer tube of white coloured polyethylene, an inner tube of polyethylene, with an extruded, tubular oxygen barrier layer intermediate the outer and inner tubes, with the inner tube and/or oxygen barrier of dark colour that is effective as a light barrier.

5. Piping as claimed in Claim 4, wherein a first, tubular tie layer is extruded onto the exernal periphery of the inner tube of polyethylene, the oxygen barrier layer is extruded onto the external periphery of the first tie layer, a second tubular tie layer is extruded onto the external periphery of the oxygen barrier layer, and the tube of white coloured polyethylene is extruded onto the external periphery of the second tie layer, so that this piping is a five layer extrusion, with the first tie layer and/or second tie layer and/or oxygen barrier layer being of dark colour effective as a light barrier.

7. Piping as claimed in Claim 6, wherein the dark coloured layer(s) is (are) grey, black, blue or brown.

8. Piping as claimed in Claim 6 or Claim 7, wherein the dark coloured layer(s) is (are) such that no more than 0.2% light penetration into the interior of the inner tube of polyethylene is permitted.

9. Piping as claimed in any preceding Claim, wherein the polyethylene, is high density cross-linked polyethylene (or similar material).

10. Piping as claimed in Claim 4 and any Claim appendant thereto, wherein the oxygen barrier layer is EVOH.

11. Piping as claimed in any preceding Claim, wherein the outer polyethylene tube is of 0.5mm wall thickness.

12. Piping as claimed in any preceding Claim, wherein the inner polyethylene tube is of 1.45mm thickness.