Plant emergencies available systems

If the plant may grow to depend on the output of a waste heat boiler to make up for inadequate capacity in the main boiler house, consideration should be given to equipping a waste heat boiler with an emergency burner system to keep steam available when waste flue gas is not available. 

Therefore most plants are equipped with a four-train independent emergency feedwater system powered by four dedicated Diesel generators. In addition, these plants dispose of an auxiliary feedwater system (start-up and shut-down system) equipped with two pumps supplied by emergency power supply. As a result there are two diverse, redundant auxiliary/emergency feedwater systems available. 

There should also be clear definitions regarding the availability of essential or safety-related plant - e.g., emergency shutdown systems, fire detection equipment, fire suppression equipment, or backup electricity supplies. These types of procedures and definitions are usually called operating rules or site safety policies (Fig. 10.3, top right). 

Nickel carbonyl should be used in totally enclosed systems or under good local exhaust. Plants and laboratories where nickel carbonyl is used should make use of air-monitoring devices, alarms should be present in case of accidental leakage, and appropriate personal respiratory protective devices should be readily available for emergency uses. Monitoring of urinary nickel levels is useful to help determine the severity of exposure and identify appropriate treatment measures. Some large-scale users of nickel carbonyl maintain a supply of sodium diethyldithiocarbamate, or Antabuse, a therapeutic agent, on hand for use in case of overexposure. 

Water. Water mains should be connected to plant fire mains at two or more poiats, so that a sufficient water supply can be deHvered ia case of emergency. The plant loop and its branches should be adequately valved so that a break can be isolated without affecting a principal part of the system. If there is any question of maintaining adequate pressure, suitable booster pumps should be iastaHed. Any connection made to potable water for process water or cooling water must be made ia such a manner that there can be no backflow of possibly contaminated water check valves alone are not sufficient. The municipal supply should faH freely iato a tank from which the water is pumped for process purposes, or commercially available and approved backflow preventers should be used. 

A system for reporting fires and alerting the plant fire brigade and the municipal fire department should be provided. This system should be as simple as possible to minimize the potential for confusion in emergencies. The preferred design is a multiplex system that alarms in the control room or some other 24-hour constantly attended location and activates visual devices, such as strobes or beacons, and audible notification devices, such as a steam whistle, air horn, or tone generator. Complete systems are available from recognized vendors. 

Larger plants are preferably equipped with two or more lines, fed by one large compounding, batching, or formulation system. Otherwise the lines are kept separate to improve availability because only one line is down during maintenance and emergency shutdowns. 

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