A gas heat pump system including an outdoor unit having a compressor, an outdoor heat exchanger, and an expansion device; an indoor unit having an indoor heat exchanger; a refrigerant pipe to connect the outdoor unit and the indoor unit; an engine to combust mixed fuel in which fuel and air are mixed; a coolant tank to store a coolant; a radiator to emit, to an outside, heat which is transferred from the engine to the coolant; and a coolant pipe to connect the coolant tank and the radiator to allow the coolant to circulate therethrough, whereby the gas heat pump system has a cooling capability between 71 kW and 85 kW, the refrigerant is a mixed refrigerant having at least 50% R32, and the refrigerant pipe is a ductile stainless steel pipe having a delta ferrite matrix structure of 1% or less based on grain area.

The present invention relates to an apparatus and method for joining a longitudinal seam in a tube, to an apparatus and method of joining a longitudinal seam in a tube in a borehole, to an apparatus and method of repairing a tube and to a pig. In an aspect an apparatus is provided for joining a longitudinal seam in a tube. The apparatus (200) includes a spool (202) for progressively unwinding a coiled member (10) into an extended form (12). The member (10) transitions from a flat form when coiled (11) to a slit tube form when extended (12), in which form the member is resiliently biased. A joining device (214) is positioned downstream of the spool arranged to provide energy to a portion of the member in its extended form to cause heating so as to progressively join together the longitudinal edges of the slit tube as the member passes the joining device. A longitudinal seam (20) is thereby formed in the tube.

The present invention relates to an apparatus and method for joining a longitudinal seam in a tube, to an apparatus and method of joining a longitudinal seam in a tube in a borehole, to an apparatus and method of repairing a tube and to a pig. In an aspect an apparatus is provided for joining a longitudinal seam in a tube. The apparatus (200) includes a spool (202) for progressively unwinding a coiled member (10) into an extended form (12). The member (10) transitions from a flat form when coiled (11) to a slit tube form when extended (12), in which form the member is resiliently biased. A joining device (214) is positioned downstream of the spool arranged to provide energy to a portion of the member in its extended form to cause heating so as to progressively join together the longitudinal edges of the slit tube as the member passes the joining device. A longitudinal seam (20) is thereby formed in the tube.

This steel sheet includes a first coated portion in which an intermetallic compound layer and an aluminum coating layer are provided on a surface of a base steel sheet in order from the base steel sheet side, a first exposed portion in which the base steel sheet is exposed, and a second coated portion in which the intermetallic compound layer and the aluminum coating layer are provided on the surface of the base steel sheet in order from the base steel sheet side, in which in a first direction which is perpendicular to a thickness direction of the steel sheet and is directed from the first coated portion to one end edge of the steel sheet, the first coated portion, the first exposed portion, the second coated portion, and the end edge of the steel sheet are disposed in this order on one surface of the base steel sheet, at least the first coated portion, the first exposed portion, and the end edge of the steel sheet are disposed in this order on the other surface of the base steel sheet in the first direction, and when viewing a cross section parallel to each of the first direction and the thickness direction of the steel sheet, the second coated portion is provided in a lower region which is located on the surface of the base steel sheet and on an inner side of the base steel sheet in the thickness direction of the steel sheet from a virtual line extending in the first direction from a boundary between the first exposed portion and the second coated portion.

This steel sheet includes a first coated portion in which an intermetallic compound layer and an aluminum coating layer are provided on a surface of a base steel sheet in order from the base steel sheet side, a first exposed portion in which the base steel sheet is exposed, and a second coated portion in which the intermetallic compound layer and the aluminum coating layer are provided on the surface of the base steel sheet in order from the base steel sheet side, in which in a first direction which is perpendicular to a thickness direction of the steel sheet and is directed from the first coated portion to one end edge of the steel sheet, the first coated portion, the first exposed portion, the second coated portion, and the end edge of the steel sheet are disposed in this order on one surface of the base steel sheet, at least the first coated portion, the first exposed portion, and the end edge of the steel sheet are disposed in this order on the other surface of the base steel sheet in the first direction, and when viewing a cross section parallel to each of the first direction and the thickness direction of the steel sheet, the second coated portion is provided in a lower region which is located on the surface of the base steel sheet and on an inner side of the base steel sheet in the thickness direction of the steel sheet from a virtual line extending in the first direction from a boundary between the first exposed portion and the second coated portion.

A method for manufacturing an electric resistance welded steel pipe having an identifiable seam portion. The method includes electric resistance welding a steel pipe, cutting an inner surface bead and an outer surface bead of the steel pipe in such a manner so as to cut: (i) a whole the outer surface bead and a part of the inner surface bead to leave an uncut portion in the inner surface bead, or (ii) a whole of the inner surface bead and a part of the outer surface bead to leave an uncut portion in the outer surface bead, coating the steel pipe with zinc phosphate, and cold drawing the steel pipe using a plug and a die to make the seam portion of the steel pipe identifiable.

A method for manufacturing an electric resistance welded steel pipe having an identifiable seam portion. The method includes electric resistance welding a steel pipe, cutting an inner surface bead and an outer surface bead of the steel pipe in such a manner so as to cut: (i) a whole the outer surface bead and a part of the inner surface bead to leave an uncut portion in the inner surface bead, or (ii) a whole of the inner surface bead and a part of the outer surface bead to leave an uncut portion in the outer surface bead, coating the steel pipe with zinc phosphate, and cold drawing the steel pipe using a plug and a die to make the seam portion of the steel pipe identifiable.

A repair welding method according to at least one embodiment is for a member in which a first end and a second end of a parent material are connected by welding and includes: a step of removing a portion including at least a part of a first heat-affected zone of an existing welded portion of the member; and a step of performing repair welding after removing the portion. In a cross-section including the parent material and the existing welded portion, all intersection portions between the first heat-affected zone of the existing welded portion and a second heat-affected zone due to the repair welding have an intersection angle between the first heat-affected zone and the second heat-affected zone of 70° to 110°.

Aspects of the present disclosure relate to methods of coating a coiled tubing string, methods of conducting tubing operations using a coated tubing string, and associated apparatus thereof. In one implementation, a method of conducting a coiled tubing operation, includes forming a tubing string. The tubing string has a central annulus, an inner surface, and an outer surface, and the tubing string is formed from a metallic material. The method also includes coiling the tubing string onto a spool, and moving a coating into the central annulus. The method also includes curing the coating onto the inner surface of the tubing string to form a layer of the coating on the inner surface of the tubing string.

Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a steel plate for structural pipes or tubes that exhibits excellent resistance to PWHT and excellent toughness at the heat-affected zone, particularly at the butting faces joined by welding, without addition of large amounts of alloying elements. The steel plate for structural pipes or tubes disclosed herein has a specific chemical composition, in which the steel plate has mechanical properties including: (a) a 0.5% yield strength of 555 MPa or more; (b) a tensile strength of 625 MPa or more; and (c) a Charpy absorption energy vE.sub.−10° C. at −10° C. at its mid-thickness part of 250 J or more, and maintains the mechanical properties (a) to (c) even after subjection to heat treatment at 650° C. for 2 hours.