Document BvQyZe7xnN4nGdDzoONpLweD4

ELECTRICAL HAZARDS GROUND CLAMP Fig 31-4. A simple low-voltage teat unit with on indicating light bulb. The diagram shows a continuity test between the ground prong of the plug and the ground wire connection to the metal shell Courts*/ Soil Iniuren Service. Inc. Leading manufacturers of electrical equip ment often maintain staffs of engineers to guide buyers in the purchase of explosionproof fittings Because of the highly tech nical nature of this field, competent engi neers should always be consulted for these needs Only fittings which have undergone ex haustive tests and meet the requirements of the Underwriters* Laboratories, Inc, for use in hazardous locations should be used (Fig 31-7) They must be of durable ma terial, provide thorough protection, and be finished to be totally resistant to atmos pheric conditions Explosion-proof fittings should be in stalled not only on new work but also on old wiring systems where alterations are being made or new equipment is bemg in stalled Observing code requirements will minimize dangers that might result from using ordinary fittings in hazardous loca tions These fittings are made of durable cast material, with roomy intenors for wiring and splices, and they are capable of with- Flg. 31-7. An explosion-proof and dusttight mercury switch which makes and breaks the circuit when the switch tilts the tube inside the mechanism. Courteiy The Appleton Electric Company 31-15