PBX systems are complex digital equipment, replete with
sensitive circuitry and electronics. And like all computers, they
are extremely vulnerable to electrical disturbance. One of the
biggest problems in PBX systems – and virtually any
microprocessor-controlled equipment – is harmonic distortion.
This is electrical ‘noise’ created by nonlinear power loads. The
result is heat that burns out sensitive circuitry.
Boilers and Fired Pressure Vessels are subject to several
dierent hazards;
- explosion, due to internal pressure of steam or water
- burning (overheating), caused by continued firing after the
water drops below a safe level
- cracking of cast iron sections, due to such things as expansion
and contraction stresses, rust growth between sections, porous
castings, and tie rods that are too tight
- bulging or bagging, usually caused by improper heat transfer
due to build-up of scale or sediment
- collapse (of the cylindrical furnace of a scotch marine boiler),
generally due to ‘low water’
Unfired Pressure Vessels, such as air tanks, electric water
heaters, steam cookers, hydro-pneumatic tanks, and process
vessels, are subject to the hazards of explosion, bulging,
cracking, and collapse (implosion).
The vessels, coils and piping that form part of refrigerating
systems can explode, collapse or crack. The most common type
of failure is cracking, which is often caused, oddly enough, by
freezing due to control failure.
An additional hazard is encountered in the operation of ammonia
refrigerating systems. Ammonia that is released by a breakdown,
such as a broken pipe, can cause heavy contamination losses,
especially in food products.
Mechanical Equipment – compressors, pumps, blowers, fans,
engines, turbines and the like – are subject to a variety of hazards.
Among the more common causes of failure are: metal fatigue,
loss of lubrication, over-speed, mechanical stress, and shock
loads. A more detailed listing appears in the separate exhibit
entitled Insurable Equipment on page 21.
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