Leak containment failure

Simpler plants are friendlier than complex plants because they provide fewer opportunities for error and because they contain less equipment that can cause problems. Often, the reason for complexity in a plant is the need to add equipment and automation to control the hazards. Simplification reduces the opportunities for errors and misoperation. For example, (1) piping systems can be designed to minimize leaks or failures, (2) transfer systems can be designed to minimize the potential for leaks, (3) process steps and units can be separated to prevent the domino effect, (4) fail-safe valves can be added, (5) equipment and controls can be placed in a logical order, and (6) the status of the process can be made visible and clear at all times. 

Characteristics of LP gases, types of fire emergencies, response strategies, liquid versus vapor release, unignited leaks, construction of LP containers and behavior during fires, and preventing container failure. 

Detection LPG, cooling tanks with water, controlled burning, shutting down leaks, fire protection, container failure, BLEVEs, direct reading instruments, vapor clouds, and ASME and DOT container types. Emergency Film Group Preview 35 Rental 150 Purchase 395... 

The spill of process materials in an SCB is an anticipated operational event Spills may range from minor seepage or leaks of small quantities of materials to a complete spill of the process contents due to operator error or due to failure of process containers. Process container failures may occur either due to spontaneous mechanical failures and/or may be induced by operator actions. Provisions for accommodating such spills have been incorporated in process equipment design in the fomn of spill trays, absorbent material, and SCB washdown systems. Clean up of the spilled material and returning the SCB to a clean operational state will be an operational Inconvenience, but will be a routine task. 

The ability of iodine to partition from water into the containment atmosphere is significant in terms of the potential consequences of a reactor accident. Partitioning assures that for many days following an accident there can be some concentration of iodine vapour in the containment atmosphere. This iodine in the atmosphere is available to leak from an intact containment or to be released in the event of catastrophic containment failure. Partitioning of iodine from water into the gas phase can also be a mechanism for radioactive iodine to b q)ass filtering systems that are quite effective at mitigating the releases of other radionuclides from reactor containment. It is the persistence of iodine suspended in the containment atmosphere more than the ehemieal or physieal form of iodine that raises risk-significant issues. 

Start of the Accident Pre-existing Leak Containment Isolation Failure Containment Bypass... 

Pressure-tubes allow the separate, low-pressure, heavy-water moderator to act as a backup hesit sink even if there is no water in the fuel channels. Should this fail, the calandria shell ilsdf can contain the debris, with the decay heat being transferred to the water-filled shield tank around the core. Should the severe core damage sequence progress further, the shield tank and the concrete reactor vault significantly delay the challenge to containment. Furthermore, should core melt lead to containment overpressure, the concrete containment wall will leak and reduce the possibility of catastrophic structural failure (Snell, 1990). 

Tanks containing liquefied gases that are kept liquid by refrigeration sometimes have electric heaters beneath their bases to prevent freezing of the ground. When such a heater on a liquefied propylene tank failed, the tank became distorted and leaked—but fortunately, the leak did not ignite. Failure of the heater should activate an alarm. As stated in Section 5.2, frequent complete emptying of a tank can weaken the base/wall weld. 

Davenport [1] has listed more than 60 major leaks of flammable materials, most of which resulted in serious fires or unconfined vapor cloud explosions. Table 9-1, derived from his data, classifies the leak by point of origin and shows that pipe failures accounted for half the failures— more than half if we exclude transport containers. It is therefore important to know why pipe failures occur. Following, a number of typical failures (or near failures) are discussed. These and other failures, summarized in References 2 and 3, show that by far the biggest single cause of pipe failures has been the failure of construction teams to follow instructions or to do well what was left to their discretion. The most effective way of reducing pipe failures is to ... 

Available refrigerants for various levels or conditions of operation may be toxic, flammable, irritating on exposure, hydroscopic, and expensive. These characteristics cannot be ignored, as large systems contain large quantities of refrigerant, and a leak or other failure can release a potentially serious condition into a building or process area. 

Boiling liquid expanding vapour explosions occur when there is a sudden release of vapour, containing liquid droplets, due to the failure of a storage vessel exposed to fire. A serious incident involving the failure of a LPG (Liquified Petroleum Gas) storage sphere occurred at Feyzin, France, in 1966, when the tank was heated by an external fire fuelled by a leak from the tank see Lees (1996) and Marshall (1987). 

The most common scenario of interest for LOPA in the chemical process industry is loss of containment of hazardous material. This can occur through a variety of incidents, such as a leak from a vessel, a ruptured pipeline, a gasket failure, or release from a relief valve. 

The main failure of equipment is a loss of process containment. The consequences depend on the properties and the amount of the leaking material and the conditions both inside and outside of process equipment. Pumps and compressors (Marshall, 1987) are perhaps the most vulnerable items of pressurised systems, because they contain moving parts and they are also subject to erosion and cavitation. Pumps and compressors produce also vibration, which may lead to fatigue failure. Both seals and bearings of pumps and compressors are liable to failure. In addition agitator systems present difficulties due to mechanical stresses, though they operate at much lower speeds than pumps. 

Liquids under pressure (pipeline leaks, pump seal failures, etc.), will be thrown some distance from the point source, while atmospheric leakages will emit at the point of release. The other characteristic of liquid releases is their flash points. High flash point liquids, not operating above their flash point temperatures, are inherently safer than low flash point liquids. Most liquid fires are relatively easy to contain and suppress while gas fires are prone to explosion possibilities if extinguished and source points are not isolated. 

If the analyst cannot cite a definite physical reason for failure to include a specific sample measurement, such as evident instrument malfunction, sample container leakage, or sample loss on transfer or injection, then there is no justification for deleting a measurement from subsequent evaluation of a total sample series. If, on injection of a sample into the chromatograph, the operator believes that septum leak is evident, the resulting chromatogram should be marked immediately and never measured or included in the subsequent results. Conversely, if he cannot cite such a reason, the resulting chromatogram must be measured and included in the overall evaluation of the study. 

With volatile treatment, the feedwater must not contain hardness of condenser-leak constituents. Since no phosphate is present to remove hardness, any contamination assumes major importance. Prompt detection and remedial action is required. Failure to take such action endangers the... 

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