A jacketed vessel for temperature control of contents within the vessel is provided. The vessel has a shell and an external jacket through which heating or cooling fluid is circulated. The jacket is formed by a length of conduit arranged in a spiral orientation around the vessel shell. The conduit has a center portion having a concave inner surface and has opposing side portions having convex inner surfaces. Edge sections of each side portion are welded to the exterior surface of the shell to form the jacket. Edge sections of adjacent arcs of conduit may be simultaneously welded to the shell in a single weld pass. The shape of the conduit provides improved heat transfer and pressure drop characteristics, as well as improvements in the vessel manufacturing process.

A jacketed vessel for temperature control of contents within the vessel is provided. The vessel has a shell and an external jacket through which heating or cooling fluid is circulated. The jacket is formed by a length of conduit arranged in a spiral orientation around the vessel shell. The conduit has a center portion having a concave inner surface and has opposing side portions having convex inner surfaces. Edge sections of each side portion are welded to the exterior surface of the shell to form the jacket. Edge sections of adjacent arcs of conduit may be simultaneously welded to the shell in a single weld pass. The shape of the conduit provides improved heat transfer and pressure drop characteristics, as well as improvements in the vessel manufacturing process.

A method of connecting together two unit elements (2, 4) of an undersea fluid transport pipe that is subjected to fatigue, by welding together two metallic or bi-metallic unit pipe elements that have been put into abutment via their respective free ends (2a, 4a), the welding being done by making three distinct weld beads (6, 8, 10), with a last weld bead (8) being deposited between two lateral first weld beads (6, 10), and being followed directly by controlled sanding of the weld beads in order to apply compression stresses on them.

Systems for multi-wire submerged arc welding including a flux-cored wire electrode comprising an internal flux, the internal flux comprising about 5% to about 70% of a carbonate compound and less than 25% of calcium fluoride (CaF.sub.2) by weight of the flux; an external flux for submerged arc welding, are provided such that, after a submerged arc welding process, the systems provide a weld metal comprising nitrogen in an amount of less than 100 ppm. Methods of performing multi-wire submerged arc welding using a flux-cored electrode and an external flux are also described.

A pressurised welding habitat comprising; a housing configured to provide a sealed chamber, a port configured to connect to a gas supply and enable pressurisation of the chamber, and a sealing unit comprising a channel, wherein the channel is moveable relative to the housing and is configured to provide sealed instrument access to the chamber.

Systems and arrangements for detecting leans and repairing damaged lining of NPP spent fuel pools filled with water. The arrangements and systems include devices that are not submerged to the spent fuel pool, including welding equipment, and devices submerged to the spent fuel pool, including a submersible repair platform for the working mechanism installation. The working mechanism includes a device for cleaning of weld seams and the surface of the spent fuel pool, and a wire cutting device, comprising a container for collection of cuttings and a pump for particulate removal. The leak sealing device is arranged in the form of a small-scale welding assembly connected to the welding equipment, and the submersible repair platform is equipped with means for its attachment to the surface of the spent fuel pool. The arrangement for repairing the lining of a spent fuel pool includes a submersible repair robot having a working unit.

A water-degradable welding purge dam apparatus for purging a weld zone of a pipe assembly having first and second pipes having respective first and second pipe ends to be welded together at a root gap. The purge dam apparatus includes a blocking plate assembly having an outer blocking plate, an inner blocking plate, and zero or more interior blocking plates. The blocking plate assembly may be formed from one or more water degradable materials to facilitate removal of the purge dam apparatus from the pipe assembly using an aqueous fluid following welding. At least one of the blocking plates may include a plurality of fluid flow apertures to aid distribution of the aqueous fluid through the blocking plate assembly. If desired, first and second ones of the blocking plate assembly may be ganged together by an interconnection assembly to form a ganged set of blocking plate assemblies.

There is described a method and associated apparatus for connecting a structure to equipment underwater, in particular for connecting a flange to a pipe under water. The pipe is provided under water, and a welding machine is provided in a welding space provided through a section of the pipe, and used to weld the flange to the end of the pipe, for example by internal metal inert gas welding.

A split-type multifunctional underwater arc welding power supply, comprising: including a shore power supply module and an underwater power supply module is provided. The shore power supply module comprises a shore power supply main circuit unit and a shore power supply control unit. The shore power supply main circuit unit comprises an input filter circuit, an IGBT full-bridge inverter circuit, an intermediate frequency transformer, and an output rectification filter circuit. The underwater power supply module comprises an underwater power supply main circuit unit and an underwater power supply control unit. The shore power supply module is provided on the shore, and the underwater power supply module is carried underwater.

A method of connecting together two unit elements (2, 4) of an undersea fluid transport pipe that is subjected to fatigue, by welding together two metallic or bi-metallic unit pipe elements that have been put into abutment via their respective free ends (2a, 4a), the welding being done by making three distinct weld beads (6, 8, 10), with a last weld bead (8) being deposited between two lateral first weld beads (6, 10), and being followed directly by controlled sanding of the weld beads in order to apply compression stresses on them.