GB2271160A

GB2271160A - High impact strength pipe

Info

Publication number: GB2271160A
Application number: GB9307097A
Authority: GB
Inventors: Yong Goo Shin
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-10-01
Filing date: 1993-04-05
Publication date: 1994-04-06
Anticipated expiration: 2013-04-05
Also published as: GB2271160B; KR950005495Y1; JP2555165Y2; GB9307097D0; KR940010389U; CN2165306Y; JPH0935U

Abstract

A high impact three-layer water service pipe has excellent impact strength, tensile strength and flattening load strength. This pipe has a triple pipe wall construction including an impact resisting outer hard layer 1, an impact resisting inner hard layer 1' and a middle hard layer 2 which is interposed between the outer and inner hard layers. The thickness ratio of the outer hard layer, the middle hard layer and the inner hard layer is 1 : 2 - 3 : 1. The outer and inner hard layers are made of a vinyl chloride material having relatively higher impact strength and relatively lower tensile strength than those of the middle hard layer. All three layers may comprise PVC and the inner and outer layers 1', 1 may include an additive of CPE. <IMAGE>

Description

HIGH IMPACT STRENGTH PIPE The present invention relates in general to water service pipes. More particularly, the present invention relates to a high impact strength three-layer water service pipe having excellent impact strength, tensile strength and flattening load strength.

As known to those skilled in the art, conventional metal water service pipes have a serious problem caused by corrosion of the metal materials. For example, known cast iron pipes or copper pipes are apt to be corroded and, as a result, cause water leakage, reduction of the amount of water supplied and water pollution such as generation of red water and white water. Furthermore, these known metal pipes generally have heavy weight and this causes the serviceability of the water service line using them to be deteriorated.

The known metal pipes, while having the aforementioned corrosion problem, nevertheless are inexpensive and have excellent weatherability and good impact resistance. In this respect, these known metal pipes have been relatively widely used for water service pipes.

In recent, there has been proposed, in order to overcome the corrosion problem of the known water service metal pipes, several types of water service pipes, such as polyethylene particle lining pipes, galvanized iron pipes and stainless steel pipes, which are prepared by uniformly applying resin particles or forming a coating layer on inner surface of conventional steel pipes. However, a disadvantage of these pipes is that they have relatively heavy weight and, as a result, the serviceability of the water service line using them deteriorates. Furthermore, they are comparatively expensive and require complex and difficult joint process for piping.

Meanwhile, vinyl chloride pipes have been occasionally used for water service pipes since they exhibit excellent resistance to inorganic acids, alkalies and oils, and furthermore, they efficiently resist salt water as well as strong corrosive soil. These vinyl chloride pipes have additional advantage in that they are nontoxic, odourless and, as a result, wholesome and have comparatively light weight.

Also, another advantage of these vinyl chloride pipes is that they are easily bonded to each other using conventional vinyl chloride adhesive, thereby simplifying the joining of piping and facilitating maintenance of the water service line.

However, these vinyl chloride pipes have a disadvantage in that their impact strengths are low and, in this respect, they can not efficiently resist outside pressure.

In addition, the known vinyl chloride pipe has an intrinsic characteristic that its impact strength is in inverse proportion to its tensile strength and its flattening load strength. Thus, if its impact strength is improved, its tensile strength and flattening load strength are necessarily reduced, while its impact strength is necessarily reduced when its tensile strength along with its flattening load strength are improved. Hence, these known vinyl chloride pipes can not be efficiently used for the water service pipes.

In accordance with the present invention there is provided a high impact three-layer water service pipe having a triple pipe wall construction including an impact resisting outer hard layer, an impact resisting inner hard layer and a middle hard layer which is interposed between the outer and inner hard layers.

The thickness ratio of the outer hard layer, the middle hard layer and the inner hard layer of this water service pipe is 1 : 2-3 : 1.

The outer and inner hard layers of this water service pipe are made of a vinyl chloride material having higher impact strength and lower tensile strength than those of the middle hard layer.

The present invention will be further described in the following detailed description of an exemplary embodiment and the accompanying drawing which is a perspective view of an embodiment of a water service pipe of the present invention.

With reference to the drawing showing a preferred embodiment of a water service pipe of this invention, the pipe 10 comprises triple wall of three layers, that is, an outer hard layer 1, an inner hard layer 1' and a middle hard layer 2 interposed between the outer and inner layers 1 and 1'.

Here, the outer and inner hard layers 1 and 1' are individually made of a vinyl chloride material which has relatively higher impact strength and relatively lower tensile strength than those of the middle hard layer 2. Also, it E preferred to determine the thickness ratio of the outer layer 1, the middle layer 2 and the inner layer 1' to be 1 : 2-3 1.

In preparation of this water service pipe, an appropriate impact reinforcement material along with a high density additive is added to the vinyl chloride material of the outer and inner hard layers 1 and 1' in order to increase the impact strength of the layers 1 and 1'. In order to improve the tensile strength and the flattening load strength of the middle layer 2, the middle layer 2 is made of a hard v-inyl chloride material having different molecular weight from that of the material of the outer and inner layers 1 and 1'.

The water service pipe has such three-layer construction that the outer and inner layers 1 and 1' have individual properties which are different from the property of the middle layer 2. In this respect, it is noted that the present water service pipe uses so-called superposition principle in which the outside impact wave length is efficiently reduced due to the property difference between the materials of the outer and inner layers 1 and 1' and the middle layer 2. In addition, the outer and inner layers 1 and 1' are isolated from each other by means of the middle layer 2. As described above, the thickness ratio of. the outer layer 1, the middle layer 2 and the inner layer 1' is determined to be 1 : 2-3 : 1 and, in this regard, the I-bearn effect of the present water service pipe is remarkably improved.

The Table 1 shows performances of the high impact water service pipe of this invention in comparison with those of the known vinyl chloride water service pipe.

TABLE 1 TABLE 1 Known vinyl chloride This high impact three pipe layer pipe pipe layer pipe Tensile 480 - 495 520 - 525 strength (at 20 C) (at 20#C) Water for 1 min. for 1 min.

pressure at 45 Kgf/cm2 at 60 Kgf/cm2 test crack, water leakage no crack, no water leakage observed observed observed observed Flattening flattening to at least flattening to contact of test 1/2 of outer diameter inner surfaces crack or rupture no crack, no rupture observed observed (230 Kg load) (490 - 505 Kg load) (230 Kg load) (490 - 505 Kg load) Impact 9 Kg impact plumb, 9 Kg impact plumb, test 100 cm height dropping: 300 cm height dropping: (at 20'C) all of 10 pipes broken. 10 pipes not broken.

90 cm : 8 pipes broken 13.5 Kg impact plumb, SO cm : 7 pipes broken 300 cm height dropping: 70 cm : 6 pipes broken 10 pipes not broken.

60 cm : 10 pipes not (the same result at 10*C) broken.

broken.

As described above, the present invention provides a high impact three-layer water service pipe made of different vinyl chloride materials. This pipe has three layers which are constructed such that the outer and inner layers have individual properties different from the property of the middle layer and the I-beam effect of the pipe is maximized.

In this respect, th's water service pipe has excellent impact strength, tensile strellyth and flatteniny load strength.

Inner, outer and middle (intermediate) layers 1,1',2 are all made of PVC. However, middle layer 2 is made of normal PVC (relatively hard in its nature) while inner and outer layer 1,1' are made of specially composed PVC (relatively soft in its nature).

Inner and outer layer 1,1' contain additive i.e. CPE (chlorinated polyethylene), which is generally used in composition of PVC for the purpose of increasing tensile strength (or in other words, decreasing impact strength) of PVC. Increase of impact strength means decrease of tensile strength, thus there is a relation of inverse proportion between impact strength and tensile strength in the nature of PVC.

The ratio 1:2:1 of inner, middle and outer layer is most effective for small diameter pipes and the ratio 1:3:1 of the same is proper for large diameter pipes. The said ratios are proved to be most effective for increasing both impact strength and tensile strength of PVC through experiment and test.

Claims

1. A high impact strength three-layer pipe having a triple layer pipe wall comprising: an impact resisting outer hard layer, an impact resisting inner hard layer and a middle hard layer, said middle hard layer being closely interposed between said outer and inner hard layers.

2. A pipe according to claim 1, wherein the thickness ratio of said outer hard layer, said middle hard layer and said inner hard layer is 1 : (from 2 to 3): 1.

3. A pipe according to claim 1, wherein each of said outer and inner hard layers is made of a vinyl chloride material having higher impact strength and lower tensile strength than those of said middle hard layer.