Safety cooling towers

Taylor, F.G., Jr. 1980. Chromated cooling tower drift and the terrestrial environment a review. Nuclear Safety 21 495-508. 

FIRE HAZARD AND SAFETY PRECAUTIONS WITH COOLING TOWERS... 

Workshops on occupational safety guidelines for cooling tower maintenance workers (and visitors such as field-service representatives). 

NOTE Observe adequate safety precautions for all cooling tower maintenance workers to protect them against not only the general occupational health and safety risks but also the special risks from Legionella. 

These are instrument system loops that are necessary to avoid a failure which could result in nonreportable environmental releases, equipment or production losses, or reduced economic life, plus all other systems and alarms that assist operations that require prooftesting. These alarms and shutdown systems include refrigeration units that have less impact or safety or environmental issues than the Class 2 units, important pump shutdown alarms, low pressure utility alarms (well water, cooling tower water, natural gas, instrument air, nitrogen), and numerous low-pressure lubrication alarms. 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [8]... 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [71 Normal Consequences—Class 3. Instrument systems that are used to alert the chemical pracess operator of a nonhazardous abnormal condition that might otherwise be undetected. The failure to react to one of these alarms may create an off-spec ificalion product such as a low-temperature alarm on certain distillation columns. These systems are not included in the prooftest program. 

A decade ago it was not uncommon to specify 85° F cold water and to select exchangers for 88 to 90° F cold water. To some engineers it seemed logical to include a small 3°F safety factor in the calculations. However, this 3°F safety factor quite often turned out to be a 50% safety factor as far as the price and size of the cooling tower were concerned. Table 3-5 indicates that a tower sized to cool 28,500 gpm from 118 to 88° F with an 80° F wet bulb would cost 361,920, or 12.70 per gpm. A cooling tower selected to cool 28,500 gpm with the 3°F safety factor or from 115 to 85° F with an 80°F wet bulb would cost 532,480, or 18.68 per gpm. This is approximately 50% more in cost, length of concrete basin and fan horsepower. 

Sudret B., Defaux G., and Pendola M. 2005. Ilme-invariant finite element reliability analysis application to the durability of cooling towers. Structural Safety, 27,93-112. 

---