Abstract: Guide and runner assemblies for uphill teeming comprise a refractory tube in a sheath with an optional body of particulate material between the inner tube and sheath. The sheath may be combustible.

Abstract: This invention is a means for aligning and securing adjacent conveyor trough structures which involves a conveyor trough means of specific design and an alignment and anchor wedge member that is easily usable to assure proper rigid connection and alignment of adjacent conveyor trough means. The alignment and anchor wedge member is of a special design and driven as a wedge between adjacent ends of the conveyor trough means to be interconnected and acts to positively align the conveyor chain support members which is of extreme importance to reduce wear and maintenance.

Abstract: An applicator is provided for coating the uncovered end portions or stubs of pipe sections after they have been welded together. A belt is maintained in tension out of contact with the pipe until the pipe stubs are welded together and coating operations are to begin. The belt is then wrapped onto the pipes forming an annular cavity about the welded stubs. Chain reinforcing mesh is also applied to the exterior of the belt for support. An expanding foam which sets into a hard coating is then injected into the cavity. Once the foam hardens and fills the cavity, the belt and reinforcement are unwrapped from the coated joint and moved away from the pipe.

Abstract: A hand manipulated tube which can be axially stacked and is able to sustain bobbins that can be stacked, one against another, at least for doubling and twisting operations comprising an outside section which is at least partially elastic radially and disposed circumferentially, and which bears protrusions positioned lengthwise in respect of an end face of a portion of the tube, and which extend radially outwards, an inner circumferential seat in the portion of the tube positioned in respect of the other end of the tube whereby the partially radially elastic side cooperates with the inner circumferential seat for the positioning of two axially stacked tubes, axial guides within the tube and possibly a radially guiding and tensioning element between one tube and another.

Abstract: The invention relates to a pipe part with a socket being provided with longitudinally extending channels. The channels extend into the wall of the socket. The socket engages a J-shaped retaining ring which forms with the socket a recess for retaining the flange of a seal that includes a sealing sleeve. The retaining ring adheres to the outer side of the socket by an adhesive.

Abstract: A dimensionally-recoverable article which is particularly suitable for the manufacture or repair of cable harnesses has a dimensionally-recoverable portion formed from a material comprising a crosslinked segmented polyether-ester block copolymer and an adhesive portion comprising a polyether-ester random copolymer which portions are bonded together to form a single integral structure.

Abstract: A sealed lay-in wireway comprised of channel members secured together in end-to-end relation with sealing flange gaskets thereinbetween and having longitudinally spaced covers having resilient gaskets extending continuously along their periphery and having a pivotally mounted bridging member extending along their open sides between the adjacent ends of their covers which shiftably mounts a sealing plate thereunder, the sealing plate having gasket material at each of its ends which bears against inwardly extending flanges of the channel members when drawn upwardly by a camming mechanism carried by the bridging member, the upper surface of the sealing plate at the same time bearing against gasket material carried by the ends of the covers to cooperatively perfect a seal at all of the joints.

Abstract: A vent cap having a quick release fastener for connecting the vent cap to a flue pipe of a furnace or other such combustion system is disclosed. The fastener is designed for attachment to a tubular stub connector of the vent cap and has a clip portion for engaging a slot in the flue pipe to lock the vent cap and flue pipe tigether between the clip portion and a shoulder portion of the fastener. The vent cap is easily disconnected from the flue pipe by rotating the vent cap about the longitudinal axis of the flue pipe to remove the clip portion of the fastener from the slot in the flue pipe and then, pulling the vent cap apart from the flue pipe.

Abstract: A crack arresting device for limiting crack propagation in welded sheet structures, is made in the form of a multi-layer section of the structure, integrally interposed therein. At least in one layer of the section there is provided at least one slot located at an angle to a probable crack propagation path.

Abstract: A flexible pipe comprising a first set of stress bearing elements extending substantially the whole length of the pipe, for accommodating maximum hoop stress resulting from flow of pressurized fluid through the pipe, and a second set of stress bearing elements extending substantially the whole length of the pipe for accommodating longitudinal stress resulting from a flow of pressurized fluid through the pipe.

Abstract: An electrical duct connector has a pipe form of essentially the same cross-section geometry as duct ends to be connected thereby, but of an outer wall diameter (or the like) corresponding to the interior diameter or the like of the duct ends so that the connector fits snugly into the duct ends. The connector may have two, three or more ends and is made of multipiece form with elongated tongue and groove connections in mating wall portions including, preferably, gaps near the ends of the tongues and teeth from the opposite portion of the split construction of any given connector to engage the gaps and preferably also comprising exterior catches for duct ends with reliefs in the connector wall to make the catches resilient and further locking element such as a pin connection at an angle elbow (if any) of the split-construction connector.

Abstract: The pipeline for the conveying of hot or cold fluids comprises metallic and rigid tubes (2) which are assembled directly end to end, a covering (5) of heat-insulating material in the form of sleeves (6) which are made on the basis of a cement filled with thermically insulating inorganic particles, with said covering (5) being disposed inside said tubes (2) and being in direct contact with the fluid conveyed by the pipeline.The thickness of the covering (5) made of heat-insulating material is determined in such a way that the expansion or contraction of the tubes (2) upon the feeding of hot or cold fluid into the pipeline remains compatible with the mechanical resistance of the tubes and that the outer diameter of the sleeves (6) is slightly smaller than the interior diameter of the tubes (2), with the annular space between said tubes (2) and said sleeves (6) being filled by a sealing material (8) which is injected under pressure and is more elastic than the material of the sleeves.

Abstract: A joint which may be used in a diving suit includes a plurality of annular members each having a piston and cylinder portion which are coupled together whereby the connecting members are connected in series. The piston and cylinder portions define chambers which are filled with oil and each connecting member has valves which enable communication of the oil between adjacent connecting members as the joint is flexed. A slidably anchored gimbal mounting is provided for each valve in order to preserve the flexibility of the joint without impeding valve action and in order to prevent pullout of the adjacent piston and cylinder portions. The piston and cylinder portions each include inner and outer annular walls and the inside surfaces of the annular walls of the cylinder portions are spherically curved. The annular walls terminate in respective circular rims which are oppositely staggered. This facilitates assembly on the annular connecting members.

Abstract: A cast-iron or steel pipe is coated with a two-component epoxy resin and then, prior to curing of the resin, is coated with a relatively thick layer of hydraulic concrete. A layer of a water-impervious bitumen is then applied over the concrete. The concrete layer does not extend over the spigot in a bell-and-spigot pipe, and a special fitting is provided for such a piece of pipe when the spigot end must be cut off.

Abstract: A telescoping conduit for directing air at moderate pressures to a waiting aircraft along a telescoping bridge is disclosed. One telescoping tube is suspended from each segment of the telescoping bridge. The tubes are coaxially supported from the bridge by adjustable brackets. A tube at one end of the bridge is suspended from its bridge segment at both ends of the tube, while the remainder of the tubes are suspended from a single end. This allows the tubes to fully telescopically extend and retract while providing support for the tubes at each end. A sealing portion at one end of the tubes is somewhat flexible to accommodate slight misalignment of the tubes. Also disclosed is a roller cage for centering the nesting tubes so that a wiper seal between the nesting tubes is not damaged.

Abstract: A gangable wireway assembly including a plurality of generally U-shaped troughs and trough covers utilized as either tandem sections or as fittings which connect the tandem sections in an elbow, tee or cross configuration. Trough covers have upstanding lips at opposite ends and drip hood flanges running along longitudinal margins which overlap flanges on the U-shaped trough. The tandem section covers include a reverse bend on one drip hood flange to interlock one margin of the cover with the trough. Adjacent trough ends are nestingly received by a connector and adjacent trough covers are overlapped by a connector cover at the juncture of adjacent cover sections. The connector cover includes a recess receiving the lips of adjacent covers and includes flanges in overlapping relationship with the drip hood flanges. One flange on the connector cover also includes a reverse bend to interlock with the associated drip hood flanges.

Abstract: This is an improved blast joint for subterranean wells which is ideally suited for applications where corrosive compounds such as hydrogen sulfide and carbon dioxide are encountered. The blast joint comprises a plurality of temperature and corrosion resistant hard rings which are in a stacked end face-to-face array, coaxially carried on a length of tubing. The rings are resiliently compressed in the array by spring washers interspaced by flat washers and this assembly is retained by end collars distally carried on the tubing. The end collars which are employed in this invention have a collet type construction; each collar comprising a clamp ring slidably received over the end of the production tubing, having an internally threaded outer end and a tapered inside wall. A collet sleeve with a tapered outside wall is received in the clamp ring.

Abstract: Plastic pipes comprising an inner and outer wall being interconnected by lengthwise extending connecting partitions, forming channels, the ends of the channels being each separately sealed by sealingly pressing the end walls of a channel to each other after these walls have been heated to a temperature surpassing the plasticizing temperature.

Abstract: The method of providing submarine pipeline adapted for connecting and repairing, providing flanges therealong at intervals and means to repair an interval length of pipeline by connecting repair pieces to part of said flanges, including preferred steps of submarine removal of a damaged interval length with surface preparation and subsequent submarine installation of a replacement interval length.

Abstract: A flexible pipe adapted for connection in a drill string, having sufficient wall thickness in order to withstand forces imposed by drilling a well. The flexible pipe has a plurality of improved, essentially circumferential cuts, each cut being through the wall thickness of the pipe. The cuts provide a pipe having a plurality of dovetail teeth and complimentary recesses on each end of the intermediate segments. The teeth on one segment are positioned in the recesses and interlocking with the teeth of the adjacent segment. Each side of each tooth consists of two reversed, intersecting semicircles. The tooth and recess interlock has sufficient clearance to form a joint which has limited relative movement in any direction between the segments.

Abstract: A method of applying a crack arrestor to a pipe section by heating and allowing the arrestor to cool and compress a layer of corrosion resistant material in the position it will occupy along the pipe length.

Abstract: A hollow body assembly wherein a circumferential flange is disposed on the outside and/or inside of each of a pair of individual elements to be connected at their connecting surfaces. Each of the flanges has a transverse outer surface which is perpendicular to the longitudinal axis of its respective individual element and an inner surface which is oblique to the transverse direction of the outer surface. A circumferential ring having an inner channel surrounds the flanges when the elements are connected, the ring having side edges for gripping the oblique surfaces of the flanges. The distance between the side edges of the ring when it is in its unstressed condition is less than the distance between the base points of the oblique surfaces of the flanges.

Abstract: A rigid multi-section split restraining tube is provided for use in manholes for containing the sewer rod, which is used in clearing sewer obstructions, and restraining it against the lateral reaction forces which are set up when the forwardly-driven axially-rotating sewer rod encounters an obstruction. The restraining tube is a series of short sections connected together by rigid links. Each section is split axially into upper and lower half sections, the lower half section being larger than the upper. The upper half section is adapted to be wound up on a reel or drum mounted on the rodding machine and stored. The lower half section, when withdrawn, may preferably be stored in an elongated U-shaped channel on the rodding machine. The upper half section is provided with a pair of lateral extending ears which are received within a pair of opposing curved slots in the sidewalls of the lower half section.

Abstract: A journal and end closure for a tubular vessel particularly a shell supported tubular grinding mill. The mill shell is conventional to the point of the journal. The journal and end closure are formed by a pair of spaced apart cylindrical members and a T-shaped ring member, each secured to one another in an end-to-end relationship by welding. An annular plate is secured by welding to the leg of the T-shaped ring member to form part of the end enclosure for the mill. The T-shaped ring member is made from a material with controlled sulphur and impurity levels. The two cylindrical sections are rolled so that the grain structure of the metal is generally parallel to the longitudinal axis of the tubular vessel. The dimensions of the T-shaped member are selected to prevent high areas of stress from being concentrated at the junction of the T-shaped member with the two cylindrical members and the junction of the annular member with the leg of the T-shaped member.

Abstract: A light-weight, thermally resistant, shock-resistant refractory for covering a water pipe in a high-temperature environment. The refractory shape is a partial cylinder including a body segment, two protuberances spaced apart from and on either side of the body segment by corresponding recesses and terminating in a void between the two protuberances. Two identical segments, when axially aligned in juxtaposition, are fitted together around a pipe such that the body segment of each refractory shape is intimately received by the corresponding void of the opposite refractory shape and the pair of protuberances of one shape are closely received and interlocked with the corresponding pair of recesses in the opposing shape to form a substantially cylindrical refractory covering around the pipe. The shape requires no additional means to support itself around the pipe.

Abstract: Tubular members of lightly alloyed weldable steel are utilized as a stiffening member for pipelines to prevent buckling and the spread of cracks in pipelines laid off the coast, either under or above water. The tubular member (R, R1) is constructed of centrifugally cast steel and is adapted to be connected to another similar member or to a standard pipe (T) of the pipeline. The member has a substantially increased thickness (2, 15) and is subjected to thermal treatment in order to obtain a homogeneous ferritic structure.

Abstract: An elongated sectional pipe 50 is formed from a plurality of tubular members 2 connected together end to end. Each tubular member 2 comprises three sections 6-8 each having a plurality of longitudinally staggered lugs 22-24. The lugs 22-24 have curved locking surfaces 26 and 28 to allow the sections 6-8 to be snapped together. A pipe 50 may be formed by consecutively snapping a plurality of tubular members 2 together from their disassembled sections 6-8 while simultaneously coupling the tubular members 2 together end to end. Conversely, the pipe 50 can be disassembled by directing the tubular members 2 one by one against a disassembly tool 60 which splits each tubular member 2 apart into its individual sections 6-8.

Abstract: Method and apparatus for fastening insulation to a pipe which comprises an adjustable crib which is fastened both to the pipe and to the insulation. It prevents the insulation from shifting along the pipe. Additionally, a system for fastening insulation to a pipe is shown which comprises at least one of the cribs which is mounted both to the pipe and to the insulation. Further, a method is disclosed for fastening insulation to a pipe which comprises the steps of securing at least one of the adjustable cribs to a pipe and then connecting the insulation to the crib.

Abstract: In combination, for receiving hot gases, a hollow cylindrical body such as a tube or vessel and an inner lining therefor formed of molded-block walls, the inner lining includes a hollow inner cylindrical member having mutually spaced-apart wedge-shaped keystones with radially inwardly narrowing cross section disposed at the outer circumference thereof, metallic anchors respectively fastening the keystones to the inner cylindrical member, and insulating blocks, respectively, entirely filling in the space between each two keystones whereby intermediate layers for connecting the insulating blocks to the keystones are dispensed with.

Abstract: A fracture or crack arrestor assembly is described for insertion into a pipeline formed of a plurality of sections to prevent the propagation of fractures in the pipeline. The crack arrestor assembly includes a body portion which is generally cylindrical in shape and which has opposite ends in open communication with the pipeline. The body portion includes wall portions which are sloped inwardly from each end thereof to an intermediate wall portion which forms a reduced diameter at the outer surface of the body portion. A cylindrical reinforcing member embraces the reduced diameter portion of the body portion. A cylindrical cover or shield is secured to and embraces the body portion and has approximately the same outside diameter as the pipeline to facilitate wrapping or coating of the pipeline. The cavity between the interior of the cover and the body portion may be filled with a suitable filler material.

Abstract: A gas riser apparatus for conducting gas from a souce of supply to a delivery point such as a meter or the like. The gas riser apparatus is defined by a plastic pipe and a metal pipe which are interconnected within the body of the apparatus by means of a metal-to-plastic pipe joint. The pipe joint includes a reinforcing metal stiffener sleeve and a nonmetallic outer sleeve tightly surrounding the metal pipe and the plastic pipe.

Abstract: This invention relates to a ventilating system of the type comprising a duct for distributing heated or cooled air with distribution pipes attached to the duct. Each pipe is attached by means of a collar which has one side connected to the duct and the opposite side providing means for holding a pipe end. The collar includes integrally formed lock means which permit formation of the collar from a strip and joining of the strip ends to provide the desired collar configuration. The lock means include a projection on one end of the collar strip, the projection defining an outer edge and angularly, inwardly extending side edges. This projection is receivable within a notch defined by the other end of the collar strip. The notch includes an inner edge and angularly and inwardly directed side edges with collar portions formed on opposite sides of the notch. The projection can be quickly inserted in the notch, and a secure relationship is achieved.

Abstract: A two-piece, interlocking insulator suitable for covering a truncated triangular pipe, the conforming insulator having a base unit, a pair of side walls convergingly extending from the ends of the base unit and terminating with an apex unit. The insulator can closely conform to the perimeter of the truncated triangular pipe of, as in another embodiment, to a ceramic fiber blanket located around the perimeter of the pipe. Each segment of the insulator has a body and a pair of spaced apart arms. When the two segments are longitudinally and conformingly aligned around the pipe, they can be urged together to form an interlocking, insulator which remains around the pipe without any other structural support.

Abstract: A box tool joint member of generally tubular configuration is adapted for securement by welding to one end of a steel tube to form a drill pipe. The box tool joint member comprises a body having a cylindrical outer periphery, an internally threaded socket at one end of the body, and a weld neck of smaller outer diameter than the body adjacent to the other end of the body. A tapered transition piece connecting the neck with the adjacent end of the body provides an elevator shoulder. A correlative pin tool joint member is welded to the opposite end of the tube to complete the drill pipe.The box tool joint member has an annular band of hard facing over the outer periphery of the transition piece and extending down over the adjacent part of the weld neck and up around the adjacent part of the body. The hard facing is corrosion resistant and has a smooth finished surface. Underneath the hard facing and extending beyond both ends of the hard facing is an annular butter layer of non-hardenable steel.

Abstract: An improved decorticating drum with a selective mode of processing is disclosed, composed of a hollow cylinder horizontally resting on support rollers and being rotatable about its longitudinal axis, being adapted to receive wood fed in at one end and discharge it at the other, in particular a decorticating drum for dry debarking including longitudinal slots at the surface thereof for the elimination of the bark, the improvement comprises detachable covers in the region of the longitudinal slots whereby a wet decorticating drum may be formed, said covers resting against the outer surface of the drum.

Abstract: A ceramic-lined pipe for hot fluids, e.g. gases or liquids from high-tempture nuclear reactors or within such reactors, comprises an outer metal-wall pipe formed internally with a lining of ceramic. The ceramic lining is constituted of a ceramic inner shell surrounded by a stress-absorbing reinforcing element in the form of a multiplicity of wires or cables or a sleeve. The reinforcing member stresses the ceramic body inwardly by way of compensation to the tensile stress caused by the thermal expansion of the ceramic inner shell and is sealed against the metal pipe wall directly or through the intermediary of another tubular member.

Abstract: A composite underground shaft lining assembly particularly suitable for use as a leak proof water conduit is formed with a plurality of annular concrete sections joined together by interposed layers of flexible joint material forming a composite concrete cylinder, with a composite steel cylinder formed of annular steel sections being arranged about the outer cylindrical surface of the composite concrete cylinder. The annular steel sections of the composite steel cylinder are joined together by spring rings located adjacent the flexible joints formed between the annular concrete sections.

Abstract: A low profile heat sealing iron for use in applying heat activatable tape in areas of very limited access, such as the sealing of periodic joints in air duct is disclosed. The low profile sealing iron requires only a few inches or less of clearance and has a tape guiding means that feeds the tape to the proper location for heat sealing as the iron is slid along the surface of the member on which the tape is being applied. Preferably, the iron has a handle of adjustable length which permits the sealing iron to be used on ducts measuring six to eight feet or more when the handle is extended, but having a handle only about three feet long or less for easy carrying and handling at other times. A method of using the low profile sealing iron to seal joints in air ducts is also disclosed.

Abstract: Two coaxial metal pipes, whose confronting extremities are each provided with a plurality of peripheral ribs of staggered height separated by two or more peripheral grooves, are interconnected by a coupling sleeve of fiber-reinforced thermosetting resin subdivided into several coaxially interleaved and independently deformable cylindrical shells each terminating in a pair of internal beads engaged in a respective peripheral pipe groove. The shells, increasing in axial tensile strength from the innermost to the outermost one, are preferably separated from one another by interposed antibonding layers of thermoplastic resin. A resinous filler can be inserted between the pipe extremities for electrically insulating them from each other. The shells of the coupling sleeve can be formed by coiling resin-coated filaments around the pipe axis, advantageously with application of an antifriction layer on each inner shell before the thermosetting material thereof has been fully hardened.

Abstract: A pipe having a sealing member (3) in an inner groove (2) at one pipe end (1). The sealing member provides a very effective seal relative to a spigot end (1a) of another pipe inserted in the pipe in question. The free ends of lip portions (6,7) of a sealing ring (4) (the cross section of which is of V-shape when undeformed) are provided with beads (8) so that behind a stiffening ring (5) surrounding said sealing ring (4) there is more volume of lip material than there is room for in the space confined by the adjacent part of the bottom of the groove (2), the exterior (1a') of said spigot end (1a), the rearmost sidewall (2') of the groove (2) and the stiffening ring (5). The pipe is preferably a plastic pipe.

Abstract: A method of reducing the formation of fines and streamers in connection with the gas conveying of plastic particles (and the resulting conveying apparatus), characterized by the maintenance of particular acute angle relationships between the longitudinal flow direction of particles and the impact direction of shot-peening previously used to condition pipe section interior wall means.

Abstract: A two-piece, interlocking laminated refractory for covering a waterpipe and method of manufacturing same having a low thermally conductive inner ceramic fiber layer, an outer ceramic fiber layer which is less thermally conductive than the inner layer and a metal mesh reinforcement secured to and disposed between the inner and outer layers. The refractory shape includes two main segments, each having a body segment, two protuberances spaced apart from the body segment by corresponding recesses and a void between the two protuberances. The two segments are fitted together such that the body segment and pair of protuberances of one segment are closely received and interlocked with the void and the pair of recesses on the opposing main segment. The inner and outer layers of the refractory are vacuum-formed by the use of a perforated vacuum mold submerged in a first and second ceramic fiber slurry.

Abstract: This invention relates to crack arrestors for arresting longitudinal propagation of a crack in pipelines carrying natural gas or highly volatile normally gaseous liquids or combinations thereof, and to methods for applying said crack arrestor to pipelines.

Abstract: A telescoping drain line for connecting recreational vehicles to a sewage system has telescoping rigid wall drain pipes having a plurality of pipe sections telescoping one within the other. A flexible hose extends through the telescoping pipes and out each end thereof and has means for attaching to a recreational vehicle drain at one end and into a sewage line opening at the opposite end thereof. The flexible hose is attached at each end of the telescoping rigid wall drain pipe to prevent the flexible pipe from collapsing or coming out of the rigid pipes. The flexible pipe will fold within the telescoping pipe for storage of the drain line.

Abstract: An insulated conduit composed of an inner structural tubing with each length or bend of said tubing having a bell socket at one end with a matching spigot joint at the other end, and so arranged that one is enabled to assemble comparitively long continuous lengths of the insulated conduit. Resting blocks are placed at appropriate position and distances within the inner structural tubing whereby energy carrying piping may be inserted within the inner structural tubing and rest upon said blocks. The energy carrying piping is protected from loss of heat energy by the insulative value of the ambient air within the inner structural tubing and also by the inclusion of inert air spaces located between a series of structural ribs which form a support between the inner structural tubing and an outer insulation jacket.

Abstract: A flexible pipe joint according to which a pair of spaced apart and opposed hard tubular bodies are interconnected with each other by means of a cylindrical rubber body with a reinforcing layer embedded therein and having an end wound around a core ring, each hard tubular body being provided between its inner end and the core ring with a circumferential rib and reinforcing member.

Abstract: A pipe construction for utilizing ocean energy including a plurality of toroidal pipe elements stacked one upon the other in coaxial relation to form a cylindrical wall of substantial diameter and length. Sealing means are provided between pipe elements to make leakproof the cylindrical wall, said pipe structure being suspended by a plurality of tension members arranged about the inner circumference of the cylindrical wall. A pipe construction having a circular or a polygonal cross sectional shape and having portions thereof of selected physical characteristics for selected depth of water.

Abstract: A plastic (polyvinylchloride-PVC) pipe is provided which is shaped to receive the end of an adjacent pipe such that the two pipes may be joined together by a tight adhesive seal in a simple and expeditious manner. In accordance with the invention, an internal peripheral channel is provided adjacent to one end of the pipe. The channel is displaced inwardly from the end of the pipe, and is entirely covered by the end of a second pipe, when that end is inserted into the first pipe. An entrance port for the channel is provided which extends through the first pipe into the channel. This port is preferably shaped to receive the nose of an adhesive gun which is used to inject adhesive through the entrance port into the peripheral channel. The adhesive used may be any appropriate adhesive, such as presently is being used to bond plastic pipes to one another. An exit port is provided which is angularly displaced from the entrance port, and which extends from the channel through the first pipe.

Abstract: A conduit used to convey particulate matter in which erosion is substantially diminished. A liner placed within the outer wall of the conduit is of ceramic material which is highly resistant to erosion.

Abstract: The tubular cooled members have straight pipes, each accommodating an insert aligned axially therewith and having a cross-section diminishing in the direction of the coolant flow in the pipe interior. These straight pipes are coupled in pairs by a bent connecting pipe fitted with an insert abutting against those enclosed in said straight pipes. The abutted pipes have the same diameters but the junctions between said pipes are displaced relative to those between the inserts, the inserts also having the same diameters at the abutted sections.