Abstract: A casing for a shell- and tube-type heat exchanger is produced by deforming two axially spaced portions of a length of tubing to make their integral peripheries either larger than or smaller than the internal periphery of an intermediate portion of the casing which is interposed between the end portions. A tubestack comprising tube elements supported by tubeplates is received within the casing, with the tubeplates being disposed at least partially within the end portions respectively. In the case where the natural bore of the tubing (which forms the internal periphery of the intermediate casing portion) is accurately sized and one of the end portions has a larger internal periphery than said bore, transverse baffles of the tubestack can have external peripheries which are accurately sized to engage the internal periphery of the intermediate casing portion. Otherwise, the baffles can have flexible tires mounted on their peripheries to engage the internal periphery of the intermediate casing portion.

Abstract: A ball or plug valve comprises a ball or plug having a through bore which is rotatable in a metal body to control the flow of fluid through a passage in the body. The ball can be rotated from the exterior of the body by means of a metal stem which is rotatably received in an opening in the metal body. The opening is stepped so as to define a first shoulder which faces the passage in the body, and the stem is correspondingly stepped to define a second shoulder which faces the first shoulder. Under normal operation of the valve, the shoulders are spaced apart slightly and a sealing ring is interposed therebetween. In the event that the sealing ring fails, the pressure of fluid in the passage presses the shoulder on the stem into contact with the shoulder on the body to create a metal-to-metal seal which prevents the escape of fluid to atmosphere through the opening. To make the seal reliable, the shoulders are shaped so that they contact each other only over the outer periphery of the stem shoulder.

Abstract: The invention provides method of securing a tubular element such as a heat exchange tube to a support such as a tube plate. The method involves inserting an over-size ultrasonically vibrating tool therein to expand the element outwardly against the internal wall of the aperture. The invention also provides apparatus for carrying out the method.

Abstract: It is important that a data transmission system should be fast, utilize a minimum of band width and be accurate in the presence of high noise levels. The invention provides a frequency shift keying data transmission system for transmission of binary coded information in which the mark of the coded pulse waveform is represented by a half cycle of one keying frequency and the space is represented by a half cycle of another keying frequency. An improvement in speed, band width utilization and accuracy at high noise levels is obtained by providing that the transmission signal is an approximately sinusoidal waveform of which the phase is continuous at the transitions, the time lengths of the mark and space symbols thereof are matched to the half time periods of the respective keying frequencies and the slope is constant at the cross-over points.

Abstract: A method of manufacturing a heat exchanger comprises temporarily suporting a number of tubes in a first mould using a plurality of removable tube plates. The first mould is then filled with a molten, low melting alloy. After the alloy has set, the assembly is removed from the first mould and the tube plates are disintegrated by solvent or chemical action. The assembly of tubes supported by the set alloy is then inserted into a second mould and plastic material is injected into the mould to form a thin shell around the tubes and alloy and may also form header tanks of the heat exchanger. Finally, the whole assembly is removed from the second mould and the alloy is melted out to leave the completed heat exchanger. The method is also applicable to the manufacture of other hollow articles having a complex internal configuration.

Abstract: A packing for a gas/liquid contact apparatus, particularly a cooling tower, comprising corrugated sheets assembled together to form a honeycomb structure. The sheets are formed with transverse ribs which project into the tubes of the honeycombs and which define liquid passages communicating between adjacent tubes. The sheets are also formed to provide the tubes with spiral guide surfaces which impart rotational motion to the gas.