Pipes and tubular conduits – Combined
Patent
1985-06-20
1986-08-19
Bryant, III, James E.
Pipes and tubular conduits
Combined
138145, 138174, 138178, 405171, F16L 104
Patent
active
046063781
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to subsea pipe lines for conveying fluids such as petroleum from an offshore wellhead. Such pipe lines are generally made up of steel pipe provided with a continuous weight coating, which in addition to its weighting function also serves to protect the steel pipe against corrosion and mechanical strains.
Conventional weight coating for subsea pipe lines typically consists of a casing of reinforced concrete surrounding a fibre-glass reinforced bituminous compound on the external surface of the steel pipe.
A problem encountered with such conventional weight coating is that cracks tend to develop in the brittle concrete casing owing to shocks and stresses during pipe transport and laying operations, resulting in pieces of concrete flaking off. Since in addition the inner bituminous coating has a rather poor adherence to the steel pipe surface, smaller or larger areas of the latter will be exposed to the sea water and consequently subjected to heavy corrosion.
SUMMARY OF THE INVENTION
The present invention provides a subsea pipe line section comprising a steel pipe provided with a continuous weight coating in the form of a relatively thick layer of a composite material consisting of granules of a relatively heavy material embedded in a plastic matrix, said composite material covered by a high strength, durable plastic tube.
The weight coating according to the invention eliminates the problem of the conventional concrete casing, since the plastic matrix effectively bends to the surface of the steel pipe, particularly if a corrosion resistant primer such as a bituminous epoxy resin has been applied to the steel surface prior to the plastic matrix. Moreover, the weight coating according to the invention, in contrast to the conventional concrete casing, is elastic and practically non-absorbent, thus providing a strong, ductile and impenetrable seal on the steel pipe surface. The smooth and hard outer surface of the new weight coating according to the invention also effectively solves the increasing problem of fishing equipment getting entangled on broken parts and reinforcing rods of concrete weight coatings on prior art subsea pipe lines. A further advantage of the new weight coating is that it will be capable of preventing excessive discharge of oil in case of a leakage occurring in the steel pipe, since the combined plastic tube and composite material has been found to withstand a pressure as high as 20 atm.
The weight coating according to the invention is primarily intended to be applied as an external casing on the steel pipe. However, if desired it may as well be applied as a lining on the internal surface of the steel pipe to protect it against corrosive fluids flowing therethrough.
The plastic matrix will preferably consist of a thermosetting resin such as epoxy, polyurethane or acrylic resin, while the heavy material embedded in the plastic resin preferably consists of a heavy metal ore, e.g. an iron ore such as magnetite, hematite or the like, in the form of particles or granules.
BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting examples of subsea weight coated pipe according to the invention will be explained in detail below with reference to the drawings in which:
FIG. 1 is a longitudinal sectional view of a pipe line section according to the invention provided with an external weight coating,
FIG. 2 is a partial enlarged view of the wall of the pipe shown in FIG. 1,
FIG. 3 is a partial, sectional view of the wall of a subsea pipe line section according to the invention provided with an internal weight coating, and
FIG. 4 is a portion view of end portions of two pipe line sections of the type illustrated in FIG. 3 at a welded junction thereof.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 the numeral 1 is a steel pipe provided with the protective weight coating according to the invention applied as an external casing on the pipe. This casing comprises a plastic tube 4 surrounding a relatively thick layer 3 of a composite mate
REFERENCES:
patent: 1544592 (1925-07-01), Murray
patent: 3267969 (1966-08-01), Mallard
patent: 4198450 (1980-04-01), Hooykaas
patent: 4338044 (1982-07-01), Titus
patent: 4395159 (1983-07-01), Karuks et al.
patent: 4437495 (1984-03-01), Zonsveld
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