Tank failures

An extremely important safety consideration for both heated and cryogenic tanks is that lower boiling Hquids must not be introduced into the tank. These Hquids can boil and cause a frothover or a violent evolution of vapor, followed by tank failure. 

Corrosive chemicals and external exposure can cause tank failure. Materials of construction should be chosen so that they are compatible with the chemicals and exposure involved. Welding reduces the corrosion resistance of many alloys, leading to localized attack at the heat-affected zones. This may be prevented by the use of the proper alloys and weld materials, in some cases combined with annealing heat treatment. 

Assuming that the probability of a tank failure is P, the probability of M failed tanks, if the failures are independent, is P, and the probability of the others not failing is (l-Pf. ... 

A fireball involving approximately 800 m (28,000 ft ) of isobutane resulted from the sphere s failure. Several BLEVEs of smaller vertical and horizontal tanks occurred soon thereafter. Tank failures were mainly seam-related. Parts were thrown in various directions up to a maximum distance of 135 m (440 ft). 

The aim of the tests was to study tank-wall performance. Nevertheless, a few data on BLEVE effects are presented by Schulz-Forberg et al. (1984). An overpressure of 130 mbar was measured at 80 m from the tank position in one of the tests, and was attributed to combustion. Temperatures and pressures at the moment of tank failure were beyond the superheat limit 345-357 K and 24-39 bar, respectively (see propane data in Table 6.1). Fireball development from one test is presented in a series of photographs. The maximum diameter was approximately 50 m, and duration was approximately 4 seconds. Fragmentation data, to the extent published, are given in Section 6.3. 

Petrochemical Plant. Hazardous Waste Tank Failure. 4.5-1... 

In the North American market, water heaters are almost always made with the cold water inlet and hot water outlet lines coming out of the top of the tank. The hot water outlet opens right into the top of the tank and so draws off the hottest water. The hot water has risen to the top of the tank because of its lower density. The cold water on the inlet side is directed to the bottom of the tank by a plastic dip-tube. In some models the dip-tube is curved or bent at the end to increase the turbulence at the bottom of the tank. This is to keep any sediment from settling on the bottom of the tank. As sediment— usually calcium carbonate or lime—precipitated out of the water by the increased temperature builds up, it will increase the thermal stress on the bottom of a gas-fired water heater and increase the likelihood of tank failure. On electric water heaters the sediment builds up on the surface of the elements, especially if the elements are high-density elements. Low-density elements spread the same amount of power over a larger surface of the element so the temperatures are not as high and lime doesn t build up as quickly. If the lower elements get completely buried in the sediment, the element will likely overheat and burn out. 

Where, of necessity, the vent pipe rises to a considerable height, excessive internal pressure on the tank may result, due to the pressure head of oil should an overflow occur. To prevent any possible tank failure due to such an occurrence a vent pipe pressure-relief device must be provided. It should be self-draining to reduce the risk of blockage, particularly when using heavy oil fuel. Codes require that these devices should not place any restriction on oil flow and must discharge within the bund area. 

High-level defense waste solutions resulting from plutonium recovery and waste processing activities currently are stored in mild steel-lined concrete tanks located underground at the U.S. Department of Energy s Hanford Site. Low radioelement solubility and extensive radioelement sorption on surrounding sediment help maintain isolation of hazardous radionuclides from the biosphere in the event of tank failure. 

Figure 2-5 Close-up of tank failure and exposed ribs.

This case history on a solvent tank failure has been reproduced with the permission of the American Institute of Chemical Engineers. Copyright 1995. It first appeared as Human Factors Case Histories of Improperly Managed Changes in Chemical Plants in Process Safety Progress, 1996. All rights reserved. [5]... 

Dr. Ronald J. Willey of Northeastern University in Boston prepared an excellent 35mm slide training package entitled Seminar on Tank Failures. Professor Willey... 

Professor Willey concluded the training session with this statement Remember that tanks are fragile. An egg shell can withstand more pressure and vacuum on a per unit basis. If we approach tanks with this concept, fewer tank failures will occur because we are aware of the care that must be taken with handling eggs and tanks. Routine maintenance is a must as well as periodic inspections.. . ... 

In 1997, the U.S. Environmental Protection Agency started publishing a bulletin entitled Chemical Safety Alert. The intent of these bulletins is to increase awareness of possible hazards. One of the earlier published Alerts that was entitled Catastrophic Failure of Storage Tanks, issued in May 1997. [5] This Alert including the concepts of tank failures of shell to bottom seam or side seam will be reviewed in detail in Chapter 8. However, to highlight recent problems created by maintenance efforts, two paragraphs were quoted from that document and repeated here. 

Dr, Ronald J. Willey of Northeastern University in Boston prepared an excellent 35miT slide training package entitled Seminar on Tank Failures. Professor Willey developed this instructional lecture material under the direction and guidance of the American Institute of Chemical Engineers Undergraduate Education Committee of the Center for Chemical Process Safety (CCPS). ... 

The "Seminar on Tank Failures" was completed in 1993 for use in universities by SACHE (.Safely and Chemical Engineering Education) members. To in< uire about cost and delivery, call l-SOO-AICbeniE from out-side ( f the United Slates, call (212) 705-8100 or by e-inail—ccps aiche.org. 

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