Method for anchorage and splicing of wires on wire-wrapped cylindrical prestressed structures

Claim 2

A process for reinforcing the cylindrical wall portion of pressure vessels and pipes, the steps comprising selecting a wire of sufficient strength and diameter as will provide the desired reinforcement when the wire is wrapped around said wall portion with a preselected open pitch, securing one end of said wire to the wall portion by welding the end of the wire to the adjoining wire hoop such that the weld deposit does not contact the wall portion, wrapping said wire around the wall portion such that the wire is wrapped with the preselected open pitch except adjacent to the welded end whereat at least about 3 thread pitch windings are provided so that there is a greater wire density adjacent to the weld, and providing a significantly greater tension in the open pitch windings than in the thread pitch windings.

Claim 3

The process of claim 1 in which that portion wire wrapped with a predetermined open pitch is provided with a tension no greater than about 60% of the wire's ultimate strength.

Claim 4

The process of claim 2 in which the wire wrapped with a thread pitch is provided with a tension of about 5% of the wire's ultimate strength in those windings subjected to the weld and a tension of about 30% of the wire's ultimate strength in the thread pitch windings adjacent thereto.

Claim 5

The process of claim 2 in which said tension is provided after the cylindrical wall portion has been wrapped by subjecting the wall portion to a sufficient internal pressure as will cause the wall portion to yield against the wound wire.

Claim 6

The process of claim 4 in which said cylindrical wall portion is a portion of a pressure vessel having hemispherical heads.

Claim 7

A process for reinforcing the cylindrical wall portion of a pressure vessel, the steps comprising selecting a wire of sufficient strength and diameter as will provide the desired reinforcement when the wire is wrapped around said wall portion with a preselected open pitch, wrapping said wire around said vessel at one end of said wall portion to provide at least two thread pitched hoops without any significant tension therein, welding the first two hoops together, wrapping at least two more hoops around said wall portion with a thread pitch without significant tension in the wire, thereafter wrapping the wire around the wall portion with the preselected open pitch without significant tension in the wire, continuing said wrapping until the opposite end of said cylindrical wall portion is approached, thereafter wrapping said wire around said wall portion with a thread pitch providing at least three closed pitch hoops, at the end of said wall portion welding the last two hoops together, cutting the excess wire from the wrapped structure near the weld, pressurizing the wrapped vessel to a preselected prestressing pressure sufficient to cause the cylindrical wall portion to strain circumferentially against the wrapped wire thereby stressing said wire wrapped with the open pitch to a level no greater than about 60% of its ultimate strength whereby said wire wrapped with a thread pitch will be stressed to a level somewhat below 60% of its ultimate strength.

Claim 8

A process for reinforcing the cylindrical wall portion of a pressure vessel, the steps comprising selecting a wire of sufficient strength and diameter as will provide the desired reinforcement when the wire is wrapped around said wall portion with a preselected open pitch, wrapping said wire around said vessel at one end of said wall portion to provide at least two thread pitched hoops without any significant tension therein, welding the first two hoops together, wrapping at least two more hoops around said wall portion with a thread pitch without significant tension in the wire, thereafter wrapping the wire around the wall portion with the preselected open pitch without significant tension in the wire, continuing said wrapping until the opposite end of said cylindrical wall portion is approached, thereafter wrapping said wire around said wall portion with a thread pitch providing at least three closed pitch hoops, at the end of said wall portion welding the last two hoops together, cutting the excess wire from the wrapped structure near the weld, pressurizing the wrapped vessel to a preselected prestressing pressure sufficient to cause the cylindrical wall portion to strain circumferentially against the wrapped wire thereby stressing said wire wrapped with the open pitch to a level no greater than about 60% of its ultimate strength whereby said wire wrapped with a thread pitch will be stressed to a level somewhat below 60% of its ultimate strength.

Claim 9

A process according to claim 6 in which said thread pitch hoops subjected to the weld are stressed to a level no greater than about 5% of the wire's ultimate strength, and the thread pitch hoops adjacent thereto are stressed to a level no greater than about 30% of the wire's ultimate strength.

Claim 10

A process according to claim 6 in which the entire length of wire is wrapped with a thread pitch.

Claim 11

A process according to claim 6 in which said vessel is provided with hemispherical heads, and the welded joint is provided over the point of tangency between the head and the cylindrical vessel wall.

Claim 12

A process according to claim 6 in which said vessel is provided with hemispherical heads, and the weld joint is provided down over the hemispherical head by a distance not greater than about two wire diameters from the point of tangency between the head and the cylindrical vessel wall.

Claim 13

In the process of reinforcing a line pipe whereby a wire is progressively wrapped around said pipe with a predetermined open pitch, and with a predetermined tension therein, a method of splicing a second wire onto the end of a completely wrapped first wire comprising wrapping the first wire onto said line pipe at said predetermined open pitch and predetermined tension therein until the end of said wire is approached, thereafter wrapping said first wire with a thread pitch and at a reduced tension which is less than said predetermined tension for at least about 3 full turns before the end of the wire is reached, welding the end of the second wire adjacent to the end of the wrapped first wire, wrapping the new wire onto the line pipe with a thread pitch and at the same reduced tension for at least 3 full turns, and thereafter wrapping the second wire with the same predetermined open pitch and predetermined tension as was the first wire.

Claim 14

In the process of reinforcing a line pipe whereby a wire is progressively wrapped around said pipe with a predetermined open pitch, and with a predetermined tension therein, a method of splicing a second wire onto the end of a completely wrapped first wire comprising wrapping the first wire onto said line pipe at said predetermined open pitch and predetermined tension therein until the end of said wire is approached, thereafter wrapping said first wire with a thread pitch and at a reduced tension which is less than said predetermined tension for at least about 3 full turns before the end of the wire is reached, welding the end of the second wire adjacent to the end of the wrapped first wire, wrapping the new wire onto the line pipe with a thread pitch and at the same reduced tension for at least 3 full turns, and thereafter wrapping the second wire with the same predetermined open pitch and predetermined tension as was the first wire.

Claim 15

A method according to claim 11 in which said wire wrapped at said predetermined pitch is stressed to a value no greater than about 60% of the wire's ultimate strength, and the wire wrapped with a thread pitch is stressed to a value no greater than about 30% of the wire's ultimate strength.