MACHINES positive displacement rotary or oscillating piston liquid and elastic fluid or elastic fluid liquid only reciprocating piston or other liquid and elastic fluid or elastic fluid liquid only non-positive displacement liquid and elastic fluid or elastic fluid liquid only ENGINES positive displacement rotary or oscillating piston liquid and elastic fluid or elastic fluid liquid only reciprocating piston or other liquid and elastic fluid or elastic fluid liquid only non-positive displacement liquid and elastic fluid or elastic fluid liquid only PUMPS positive displacement rotary or oscillating piston reciprocating piston or other non-positive displacement In this subclass, the following terms are used with the meanings indicated: "pipe" means a conduit of closed cross-section, which is specially adapted to convey fluids, materials or objects; "hose" means a pipe, as defined above, which has flexibility as an essential characteristic. Attention is drawn to the following places: Tube connectors, tube couplings or branch units, specially adapted for medical use Perforated pipes Pipe-laying vessels Adaptation of hose constructions for refuelling aircraft during flight Arrangements of hoses in apparatus for transferring liquids, e.g. fuel, from bulk to vehicles or portable containers Fastening of pipes or cables to bridges Water supply installations Means for connecting water-closet bowls to the flushing pipe Siphons for water-closets Pipes or fittings specially adapted to sewers Down pipes for roof drainage; Clamping means therefor Vertical ducts, channels in buildings, e.g. chimneys Air ducts for ventilation of mines or tunnels; Connections therefor Suspension devices for tubes or the like in mines or tunnels Gas flow silencers or exhaust apparatus for machines or engines Conduits, junctions for lubrication systems Thermal insulation of vessels not under pressure for storing liquified or solidified gases, e.g. Dewar flask Water tubes of steam boilers Joints, connections for chimneys or flues Connecting circulation pipes to heaters Arrangements for sealing elements into header boxes or end plates of heat-exchangers Structural association of coolant tubes with headers or other pipes in nuclear reactors Protective tubing or conduits for electric cables Installations of electric cables or lines on walls, floors or ceilings Installations of electric cables or lines in walls, floors or ceilings LAYING OR RECLAIMING PIPES SUPPORTING , , PIPES , PIPE JOINTS Constructional kinds non-disconnectable screw-threaded with separate joints: pressing member; sleeve or socket; flanged joints ; ; bends or siphons other joints Functional kinds with self-tightening sealings adjustable or allowing movement with fluid cut-off means of quick-acting type for double-walled or multi-channel pipes branching pipes, joining pipes to walls special for hoses , , special for pipes: of plastics; of brittle material ; PIPING UNITS Cleaning features Compensation devices Heating or cooling Accessories PROTECTION: AGAINST DAMAGE; CORROSION OR INCRUSTATION; THERMAL INSULATION ; ; Group takes precedence over groups . Groups and take precedence over other subgroups Pigs or moles specially adapted for particular applications are classified in the relevant places for the applications, e.g. stopping flow from or in pipes or hoses ; repairing pipes ; applying liquids or other fluent materials to the inside of tubes ; cleaning pipes or tubes or systems of pipes or tubes ; welding or cutting ; earth drilling ; cleaning chimneys ; cleaning internal or external surfaces of heat-exchange or heat-transfer conduits ; measuring, testing ; inspection of vessels in nuclear reactors ; inspection or maintenance of pipe-lines or tubes in nuclear installations ; installing electric, or combined optical and electric, cables or lines . In this group, it is desirable to add the indexing codes of group .