Pressure failures

Direct water spray cooling must be carried out with care. The spray chamber must be designed to ensure complete evaporation of all Hquid droplets before the gas enters the baghouse. Spray impinging on the chamber walls can result ia a dust mud iaside the chamber and any increase ia gas dewpoint may result in baghouse problems or atmospheric plume condensation. Spray nozzle wear can result in coarse or distorted spray and wetted bags, and water pressure failure can cause high temperature bag deterioration. 

External-pressure failure of shells can result from overstress at one extreme or n om elastic instability at the other or at some intermediate loading. The code provides the solution for most shells by using a number of charts. One chart is used for cylinders where the shell diameter-to-thickness ratio and the length-to-diameter ratio are the variables. The rest of the charts depic t curves relating the geometry of cyhnders and spheres to allowable stress by cui ves which are determined from the modulus of elasticity, tangent modulus, and yield strength at temperatures for various materials or classes of materials. The text of this subsection explains how the allowable stress is determined from the charts for cylinders, spheres, and hemispherical, ellipsoidal, torispherical, and conical heads. 

Most electrical failures are caused by external problems, such as a malfunctioning transformer, a thunderstorm, or a car hitting a power pole. Gas and water pressure failures are often caused by problems within the building itself, such as somebody shutting off a valve in order to make a repair without notifying those concerned. A system must be established whereby all affected by such a shut-down will be informed well in advance. 

Faucets chosen by the engineering firm were equipped with antisiphoning devices. The laboratory operator had specified their locations but had failed to check whether the local code required the expensive anti-siphoning type. The bench-mounted outlets installed for use with condensers and similar devices, however, were not of the anti-siphoning type, even though in this particular laboratory, the latter would be far more likely to draw water back into the system in case of pressure failure. 

Overheating in a vacuum evaporator initiated accelerating polymerisation-decomposition of (endothermic) dicyanobutene, and the rapid gas evolution eventually caused pressure-failure of the process equipment. 

Hydraulic high-pressure failures also give relatively small tears compared to pneumatic failures, which are destructive. Rapidly expanding gases give large tears and can propel missiles, drums, and vessels great distances. 

High-pressure failures are as likely to occur in a pipe or pipe system as they are in vessels. The maximum internal pressure for pipes is calculated using Equations 12-4 and 12-5. 

In a first full scale attempt at a new polymerisation process, the thermally unstable initiator was charged and heated to reaction temperature, but there was then an unforeseen delay of an horn before monomer addition was started. The rate of polymerisation effected by the depleted initiator was lower than the addition rate of the monomer, and the concentration of the latter reached a level at which an uncontrollable polymerisation set in which eventually led to pressure-failure of the vessel seals. Precautions to prevent such occurrences are detailed. In another incident, operator error led to catalyst, condensing styrene and acrylonitrile being ducted into an unstirred weighing tank instead of a reactor. When the error was recognised, the reacting mixture was dropped into drums containing inhibitor. One of the sealed drums had insufficient inhibitor to stop the reaction, and it slowly heated and eventually burst [1], The features and use of... 

The ProteomeLab PA800 instrument was set up to analyze a sequence of five different labeled rMAb samples with a total of 10 duplicate injections. On many occasions, the electrophoretic analysis of approximately 60% of the injections did not take place due to pressure failures in the instrument. Upon closer inspection, some of red rubber caps of the gel matrix-containing vials were missing, electrodes were bent, and capillaries were broken. Additionally, it was observed that the interface block was coated with a sticky film of gel matrix. It was apparent that the build-up of gel buffer was causing the red rubber caps to remain stuck to the interface block and interfere with the contact of vials in subsequent steps. To improve the removal of gel buffer, the interface block and the surrounding areas were carefully flushed with deionized water. Then, cotton swabs were used to wipe the grooves on... 

Reduction in strength of the pipe or vessel, which may ultimately fail under its internal pressure failure of a pipe is defined here as resulting... 

Hanford and Joyce placed great emphasis on the precautions which are required for the safe handling of tetrafluoroethylene, particularly at elevated pressures. Failure to provide for the adequate control of temperature and efficient agitation may lead to an increasingly rapid reaction and eventually a violent explosive decomposition of the monomer to carbon and CF4 (Kiyama, Osugi, and Kusuhara Teranishi). 

Caution. In order to seal off sections of the combustion tube, the oxygen pressure in the system must be about 50 torr below atmospheric pressure. Failure to reduce the internal pressure will prevent a good end seal and may cause a hole to develop during the sealing process. 

Then, look at the system as a whole. A simple visual inspection of a system can sometimes show the problem immediately. Is everything connected properly Are there any gas leaks causing pressure failure or loss of gas Are valves connected properly, and turned on or off, at whatever setting they should be for the system to work ... 

As in dust collection, where surface coatings have been available for many years, the treatments are designed to present a microporous structure to the slurry which effectively restricts the penetration of particles to all but a few micrometres in depth. Consequently, a filter cake quickly forms on the surface of the coating and by restricting the particles to the surface, the same cake can be easily discharged at the end of the filtration cycle. Unlike the coatings in dust collection, however, the microporous structure in liquid applications has to withstand much higher pressures. Failure to do so will result in structural collapse and premature pressurisation of the filter. 

The relations between failure deviatoric stress Oj O3 and plastic strain Ep under different confining pressures are shown in Figure 8, which shows that under constant confining pressure, failure stress decreases with accumulation of Ep. Mohr-Coulomb criterion is used as failure criterion. 

Bolted joints are subject to cychc changes in forces that want to pull the joints apart. That s why all threads in a stud and nut are required to assure full performance of the connection. Missing threads put excessive stress on the remaining threads which can lead to their pressure failure. 

We recommend that you install a pressure-relief valve that releases pressures above 2000 psig (140 bar) on each main gas line, to protect downstream equipment from high-pressure failures. The best location for the device is after the regulator shutoff valve (Figure 10.17). Pressure-relief valves on nonflammable gas lines need not be vented to a hood, but be sure to direct the vents downward (away from operator). 

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