Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1991-09-17
1994-01-04
Rosenbaum, Mark
Metal working
Method of mechanical manufacture
Assembling or joining
295272, B23P 1100
Patent
active
052748979
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing rubber-ring steel jointed pipe junctions having high internal and external long term corrosion protection, tight pipe end tolerances and being capable of withstanding high operating pressures. Whilst the invention is according to one embodiment directed towards and primarily described for producing steel pipe to be used in underground pipelines, it is anticipated that the invention is suitable for other forms of pipelines such as overground installations.
Earlier corrosion protection methods for the outer surface of underground pipelines have utilized bituminous enamels, whilst more recently the application of high quality plastic coatings such as polyethylene (PE) have been used. Both these methods of corrosion protection have been used in conjunction with cathodic protection systems. Typical prior art corrosion protection methods also utilize epoxy or cement linings for the internal surface of the steel pipe.
Corrosion protection utilizing coatings such as bituminous coatings have the major disadvantage that they create an effect known as the area effect, resulting in accelerated local corrosion if the coating is damaged. This often occurs as a result of abrasion or impact during laying of pipes.
Generally, a weak point in a pipeline occurs at the junction of pipes due to the fact that it is a site where the necessary elements to create electrolytic corrosion are present. It is critical that pipe joints be provided with effective resistance against corrosion however, in the past this has proved to be difficult.
At pipe joints it is necessary to provide &means for the purpose of preventing ingress of moisture which may precipitate corrosive processes. Furthermore, it is necessary to provide means to prevent the setting up of any electrolytic corrosion process. Pipe joints typically comprise the mating of a socket end (female part) and a spigot end (male part).
The socket end preferably has an internal groove into which a rubber ring fits to effect sealing of the joint.
Typically, the rubber-ring socket end of the pipe has previously been uncoated causing further major problems associated with use of the above-mentioned corrosion protection methods. The failure of such pipes resulting from corrosion of the pipe ends arises from the ingress of moisture and corrosive agents at the pipe joint.
In order to overcome the problems associated with the corrosion of pipe ends, the use of plastic coatings on the outer surface of the pipe has been extended to cover the internal surface of the rubber ring socket end of the pipe. Even though such practice has marginally improved the corrosion protection for such pipes the known methods of producing rubber ring socket ended steel pipe have not been adequate for producing economical and easy to assemble pipe having the outer plastic coating extending to the internal surface of the pipe joint. The major drawbacks stem from the critical tolerances required for the efficient mating of the pipe joint such that high operating pressures may be withstood and the increased difficulty associated with laying pipelines having the plastic coating extending to the internal surface of the pipe joint.
The present invention seeks to ameliorate the problems associated with rubber ring socket end joint pipes which have previously utilized an outer plastic coating which extends from the outer surface around the socket end to the inner surface of the socket end. The present invention therefore seeks to provide a method for forming a coated pipe junction of two pipes having a spigot end married to a socket end, each of said pipe ends having its outer surface covered with a protective layer, which extends around the socket end providing protection to the inner surface of the socket end. In one broad form according to the method aspect, the invention comprises the steps of: requenching socket end if it is oversized; ends; time/temperature function process;
In another form the present invention provides a method for forming a coated pipe end
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Aylen Brian A.
Mieszelewicz Gienek
Hansen Kenneth J.
Rosenbaum Mark
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