Rupture work

Steel fibers improve the thermal shock rupture work. In other words, they improve the thermal shock resistance of the lining and its capability to stay in one piece upon rupture and act as a crack stopper. The thermal limits in refractories, of course, depend on the type of steel alloy and service conditions. Furthermore, they can still be effective under reducing atmospheres at temperatures above 1600°C like in gas lances for steel treatment. Under normal or oxidizing atmospheres, castables containing Cr-Ni-alloyed steel fibers should not be exposed to temperatures >1200°C. 

Hydrophobic silica defoamers work on a basis which may not be chemical at all. They are basically finely divided sohd sihca particles dispersed in a hydrocarbon or silicone oil which sei ves as a spreading vehicle. Kulkarni [Ind. Eng. Chem. Fundam., 16, 472 (1977)] theorizes that this mixture defoams by the penetration of the silica particle into the bubble and the rupture of the wall. Table 14-23 hsts major types of defoamers and typical applications. 

Mechanical agitation is needed to break up the gas bubbles but must avoid rupturing the cells. The disk turbine with radial action is most suitable. It can tolerate a superficial gas velocity up to 120 m/h. (394 ft/h) without flooding, whereas the propeller is limited to about 20 i7i/h (66 ft/h). When flooding occurs, the impeller is working in a gas phase and cannot assist the transfer of gas to the liquid phase. Power input by agitation and air sparger is 1 to 4 W/L (97 to 387 Btu/[fF-h]) of liquid. 

The hoop stress in the tube under the working pressure of 50 bar (5 MPa) is 5 MPa X 50 mm/5 mm = 50 MPa. Creep data indicate that, at 900°C and 50 MPa, the steel should fail after only 15 minutes or so. In all probability, then, the failure occurred by creep rupture during a short temperature excursion to at least 870°C. 

However, too great a separation, and overdesign may oeeur. The overload eondition is represented by a unique stress, whieh is very mueh greater than the working stress, applied suddenly whieh eauses only the weak link to failure due to stress rupture. 

Note, a eomprehensive list of failure modes and eauses of failure for meehanieal eomponents is provided by Dieter (1986). These tables are partieularly useful when assessing the likely stress rupture failure meehanism for reliability work. 

Rupture discs are also used below relief valves to protect them from corrosion due to ves.sel fluids. The rupture disc bursts first and the relief valve immediately opens. The relief valve reseals, limiting flow when the pressure declines. When this configuration is used, it is necessary to monitor the pressure in the space between the rupture disk and the relief valve, either with a pressure indicator or a high pressure switch. Othei-wise, if a pinhole leak develops in the rupture disk, the pressure would equalize on both sides, and the rupture disk would not rupture at its set pressure because it works on differential pressure. 

The client insisted on a test. The smoke detectors worked, and the explosive charge operated, but the cutter did not cut the rupture disc. The explosive charge could not develop enough pressure because the volume between it and the rupture disc was too great. The volume had been increased as the result of a change in design installation of a device for discharging the halon manually. 

The investigation following the accident showed that the pipeline rupture was due to stresses induced in, and possibly by damage to, the pipeline resulting from its repositioning three months before. This work had occurred in conjunction with road work on the highway adjacent to the accident site. The pipeline had been dented and gouged. 

In accidental releases, pressure within a vessel at time of failure is not always known. However, depending on the cause of vessel failure, an estimate of its pressure can be made. If failure is initiated by a rise in initial pressure in combination with a malfunctioning or inadequately designed pressure-relief device, the pressure at rupture will equal the vessel s failure pressure, which is usually the maximum allowable working pressure times a safety factor. For initial calculations, a usual safety factor of four can be applied for vessels made of carbon steel, although higher values are possible. (The higher the failure pressure, the more severe the effects.)... 

No No Flow Excess ammonia in reactor. Release to work area. 1. Valve A fails closed. 2. Phosphoric acid supply exhausted. 3. Plug in pipe pipe ruptures. Automatic closure of valve B on loss of flow from phosphoric acid supply... 

The margin between the maximum allowable working pressure and the operating pressure must be considered in the selection of a rupture disk. 

The burst pressure maximum cannot exceed the MAWP of the vessel. Depending on the situation, it may be necessary to work backward to the operating pressure maximum to see if this is usable. Table 7-9 summarizes t) pical rupture disk characteristics noting that the maximum normal operating pressure of the system is shown as a function of the rupture disk bursting pressure, P. ... 

---