Abstract
Pressurized storage tanks are robust structures and catastrophic failures are very rare events. Nevertheless, owing to the rapid rate at which the liquid contents will be released from an open valve or a fractured pipe and the subsequent flashing of the liquefied gas, these types of storage are often the criteria by which a site is classed as a major hazard under the Control of Industrial Major Accident Hazards (CIMAH) Regulations. The listed materials include ammonia, chlorine, ethylene oxide and flammable gases (boiling point <20°C).
Methods of predicting leakage rates from various types of breach are presented with tables of physical property parameters for the more common materials, which simplifies the calculation of leakage rates. Brief details are given of some notable accidents involving liquefied gas storage failures to illustrate the following lessons for designers:
Continually review the field data concerning chemical attack from contaminants, particularly of the stress corrosion type. Ensure that materials will retain adequate strength at the temperature extremes that may be encountered during abnormal conditions. Design and locate fixtures and fittings so that they are operable and maintainable, paying particular regard to draining facilities. Continually update the codes for passive and active protection against fire and impact, in the light of losses occurring worldwide; for example by abstracting reports from Lloyd's Register. Be alert during hazard and operability study reviews to chance contamination of the tank contents with other process fluids which can cause the tank to become a ‘eactor vessel’ with rapid evolution of heat and pressurized gas.
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