Failure cooling systems

The ACoP relating to PUWER specifically identifies examples of hazards that the regulations cover. The ACoP provides an example of a risk of overheating or fire due to Friction (bearing running hot, conveyor belt on jammed roller), electric motors burning out, thermostat failure, cooling system failure. ... 

Cooling System Corrosion Corrosion can be defined as the destmction of a metal by chemical or electrochemical reaction with its environment. In cooling systems, corrosion causes two basic problems. The first and most obvious is the failure of equipment with the resultant cost of replacement and plant downtime. The second is decreased plant efficiency to loss of heat transfer, the result of heat exchanger fouling caused by the accumulation of corrosion products. 

Failures of the inner ring of the extruder cooling system were occurring with increasing frequency. Six failures had occurred over a 2-month period. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

Loss of Heat Sink Failure of heat transfer between the primary and secondary cooling systems requiring emergency cooling. 

Loss of River Water Failure of the river water supply to the once-through secondary cooling system requiring conservation of the water on hand. 

Excess sulfur dioxide feed to a chlorine dioxide reactor, leading to excessive exothermic reaction, combined witli failure of the cooling system... 

Successive failures of a chemical reactor s cooling system in days is ... 

Bums and Hazzan demonstrated tlie use of event tree and fault tree analysis in tlie study of a potential accident sequence leading to a toxic vapor release at an industrial chemical process plant. The initiator of tlie accident sequence studied is event P, the failure of a plant programmable automatic controller. Tliis event, in conjunction willi the success or failure of a process water system (a glycol cooling system) mid an operator-manual shutdown of tlie distillation system produced minor, moderate, or major release of toxic material as indicated in Fig. 21.4.1. The symbols W, G, O represent tlie events listed ... 

W failure of process water system G. failure of glycol cooling system... 

In Section 21.4 tlie effects of the release of toxic vapors were considered in connection witli an accident sequence initiated by the failure of a plant programmable automatic controller. In tliis study, event tree analysis and fault tree analysis led to identification of tlie glycol cooling system circulation pumps as components meriting high priority for inspection. 

Cooling system failure could occur due to failure of pumps or controls supplying cooling media to the reactor vessel jacket, coils, or overhead reflux condensers. Piping to or from the condensers could become plugged or any of the heat exchange surfaces could become excessively fouled. 

Total system failure/cooling liquid not being pumped... 

Heating/ control system failure such that the heating remains on in steps 3 and 4 and the cooling system fails to. come on during step 3.. 

Despite the considerable effort that has gone into developing these indices, they are not the panacea for accurate and objective predictions and evaluation they are sometimes made out to be Attempts to reduce or overcome all the limitations inherent in LSI are doomed to failure in cooling systems, especially under today s wide spectrum of operating conditions and constraints. 

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