Fittings conduit sealing

Explosion-proof enclosures are characterized by strong metal enclosures with special close-fitting access covers and breathers that contain an ignition to the inside of the enclosure. Field wiring in the hazardous environment is enclosed in a metal conduit of the mineral-insulated-cable type. All conduit and cable connections or cable terminations are threaded and explosion-proof. Conduit seals are put into the conduit or cable system at locations defined by the National Electric Code (Article 501) to prevent gas and vapor leakage and to prevent flames from passing from one part of the conduit system to the other. 

Conduit and cable sealing fittings as shown in Figures 17-25 and 17-26 are provided for the following purposes ... 

Special sealing fittings (not yet commercially available) are required for cables and conduits connected to process connections that depend on a single seal, diaphragm, or tube to prevent process fluid... 

Molded ABS parts are used in both decorative and protective applications in communications equipment like telephones (see Fig. 6-3), and for appliances, business-machine housings, safety helmets, camper tops, pipe fittings, shoe heels, and so on. Chrome-plated ABS has replaced die-cast metals in plumbing hardware and auto grills, wheel covers, and mirror housings. Some typical products vacuum-formed from extruded ABS sheet are refrigerator liners, luggage shells, tote trays, mower shrouds, boat hulls, and recreational vehicle parts. The possible extruded shapes include weather seals, conduit, pipe for drain-waste-vent (DWV) systems, and the like. 

Check the position of the meter. The Electricity Supply Regulations require it to be installed in the consumer s premises unless it is more reasonable for it to be located elsewhere, in which case it should be accessible to the consumer. This is more likely to occur in blocks of flats and housing in multiple occupation. In such premises the supply authority may bring in only one service cable on to a busbar and then feed each tenant via cables in conduit or sometimes in MIMS cable. The latter is not a good choice because the insulation is hygroscopic and if the end seals fail, the cable can break down. It may also fail if subject to HV transients, so such cables should be fitted with suppressors. If the conduit or sheath of the MIMS cable is used as the earthing conductor, check that the connections are satisfactory and of low resistance and any joints in the conduit provide adequate continuity. 

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