Pipes and tubular conduits – Reinforced – With embedded element
Patent
1994-08-17
1996-12-03
Bryant, III, James E.
Pipes and tubular conduits
Reinforced
With embedded element
138129, 138144, F16L 1100
Patent
active
055798098
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite construction of pipe for use in the oil, gas, water and chemical industries.
2. Discussion of Prior Art
It is known to manufacture pipe by the helical winding of a plurality of metal strips and which strips are embedded in a plastics material matrix.
U.S. Pat. No. 4,657,049 describes the manufacture of such pipe by helically winding at least one metallic reinforcing strip onto a mandrel, the strip being coated with and embedded within a polymeric bonding material. The tube is thus formed of a plurality of successive helical convolutions of metal strip, completely embedded in the polymeric material. In this construction the polymeric material provides only a limited degree of corrosion resistance and hence is not suitable for many pipe applications.
U.S. Pat. No. 4,351,364 describes a similar method of tube construction, but the tube also has inner and outer linings of resin impregnated glass-fibre layers. The glass-fibre layers comprise woven cloth and chopped fibre strand mat. The purpose of the inner lining is to provide corrosion resistance and a low flow resistance, whilst the purpose of the outer lining is to provide resistance to environmental conditions. Whilst the glass-fibre reinforced linings on the inside and outside of the pipe enhance the resistance to corrosion, abrasion and other environmental conditions, they do not significantly improve the strength of the pipe, nor do they provide optimum corrosion resistance owing to the porosity which is inevitably retained within the glass fibre mat and cloth.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a pipe having a construction which endows it not only with corrosion and abrasion resistance, but also with enhanced strength and stiffness. It is a further object to provide a pipe construction which when used in high pressure applications will produce a leak failure mode at elevated pressures close to ultimate burst pressure.
According to a first aspect of the present invention there is provided a pipe having inner and outer linings of fibre reinforced plastics material, the inner and outer linings having therebetween a core of helically wound steel strip, the steel strip being embedded in a plastics material matrix wherein the inner and outer linings are filament windings.
The filament windings may be mono-filaments or may be wound from multi-filament tows.
The filament windings may be laid at an angle of + and -55.degree. relative to the pipe axis, with an error margin of + or -5.degree.. A winding angle of + and -55.degree. is chosen where it is desired to achieve optimum balance of hoop and axial loads, such as in the case where a cylindrical pipe has to withstand full pressure and loads. The precise angle is chosen so as to suit the operating requirements of the pipe.
Alternative layers or groups of layers of filament windings may be laid at different positive and negative angles with respect to the pipe axis and to each other.
It has been found that the use of filament wound fibre-reinforced inner and outer linings not only further enhances the resistance to corrosion, abrasion and environmental attack, but also imparts additional strength and stiffness to the complete pipe. The degree of additional strength and stiffness may be determined by calculation, but will depend upon the fundamental lining and strip material properties, the ratio of lining to total steel thickness and the helical angle of lining windings to the pipe axis. Because of the additional strength imparted by the filament wound linings, it has been found that the number of steel layers may be reduced to produce a pipe of a given strength, thus making the pipe more economic to produce and lighter in construction. Furthermore, the use of filament winding is capable of producing a higher integrity, lower porosity resin matrix than corresponding prior art constructions. Prior art tube constructions employing glass-fibre reinforced plastics (GRP) ar
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Dabinett John
Millward William A.
Bryant III James E.
Royal Ordnance Plc
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