Fusion Plastics Ltd.

Vectstar Limited

Vecstar Limited

Brian Glaves

David M Kenworthy

Eric Bridgstock

David A Bilton

In an electron-fushion welding process a fault, e.g. due to incorrect assembly of the pipe joint components, is detected by sensing the welding current and emitting a signal to actuate an audible or visible alarm and/or to interrupt the welding process, if the welding current increases unexpectedly. A reference signal dependent upon the current dependent signal produced by the sensor and RMS to DC converter at a time t.sub.1 is held by a converter and is compared by a comparator with the current dependent signal transmitted through converter at subsequent intervals. So that the device does not react to transient current increase a delay arrangement delays the output signal for a given time.

Fault detecting device for welded pipe joints

An electro-fusion fitting for coupling thermoplastic pipes incorporates a heating coil (2) and has a resistor (6) with a value chosen in accordance with the power to be supplied to the coil connected between a main terminal (4) and an auxiliary terminal (5). Control apparatus is adapted to sense the resistance value and supply electric current to the coil for a predetermined time set automatically according to the resistance value.

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South Yorkshire, United Kingdom

Brian Glaves