Venting processes

The European philosophy on area classification varies from that of the United. States and Canada. Specifically, in Europe and most other inter national areas, the Zone concept is utilized. An area in which an expio sive gas-air mixture is continuously present, or present for long perioiK of time, is referred to as Zone 0. The vapor space of a closed, but vented, process vessel or storage tank is an example. An area in which an explosive gas-air mixture is likely to occur in normal operations is designated Zone 1. An area in which an explosive gas-air mixture is less likely to occur, and if it does occur will exist only for a short time, is designated Zone 2. Zone 0 and Zone 1 correspond to Division 1 in the U.S. and Canada System. Zone 2 is equivalent to Division 2. 

WTien the relief device relieves, the explosion pressure falls off, but then it increases faster than in the beginning due to the opening of the relief when the flame front is distorted creating an acceleration of the combustion process [54]. Thus, there are two pressure peaks in the course of the relieving (1) at the activation of the relief device due to pressure buildup in the vessel, and (2) at the end of the combustion reaction. The first pressure is always greater than the second. The second pressure rise is created by turbulence during the venting process [54]. 

Storm of Nov. 15-17, 1966. The fission product ratio data by nuclear event for this storm are given in Table VII. The storm occurred 18 days after the reported Chinese fourth nuclear weapon test of about 20 lalotons on Oct. 28, 1966 and 190 days after the Chinese third nuclear explosion of about 200 kilotons on May 9, 1966. Also listed is the series of tests conducted by the French in the Southern Hemisphere (near Tahiti) in the time period between these two Chinese tests. A further possible source of fission products was the vented U.S.S.R. underground nuclear explosion of Oct. 27, 1966 (14). The extent of venting is not reported, and contributions to the storm deposition, if any, would appear as part of the fission products from the China-3 explosion. However, the venting process may result in significant fractionation of the fission products. 

The primary purpose of a safety relief valve (SRV) is the last protection of life, environment and property in this process industry by safely venting process fluid from an overpressurized vessel. It is not the purpose of a safety valve to control or regulate the pressure in the vessel or system that the valve protects, and it does not take the place of a control or regulating valve... 

A tank of 60-m1 capacity contains steam at 5,000 kPa and 400°C. Steam is vented from t tank through a relief valve to the atmosphere until the pressure in the tank falls to 4,000 kPa. If venting process is adiabatic, estimate the final temperature of the steam in the tank and the mass steam vented. 

A tank of 50-ni capacity contains steam at 4500 kPa and 673.15 K (400°C). Steam is vented from tile tank tiirough a relief valve to tlie atmosphere until tlie pressure in the tank falls to 3500 kPa. If tlie venting process is adiabatic, estimate tlie final temperature of tile steam in tlie tank and tlie mass of steam vented. 

Yeo, S. D., Debenechi, P. G., Radosz, M., and Schmidt, H. W. (1993) Supercritical anti-sol-vent process for substituted para-linked aromatic polyamides phase equilibrium and morphology study. Macromolecules 26, 6207-6210. 

Chemical reaction models of seafloor hydrothermal vent processes and accompanying sulfur isotopic distribution pathways illustrate the capabilities of coupling EQPS S with EQ6 calculations, including the extent of differences that can exist due to the isotopic bounding condition assumptions described above. 

K. Assuming there is no heat transfer between the gas and the tank, find the pressure in the tank at the end of the venting process and the fraction of the initial mass... 

Downcomer trapouts seldom provide sufficient residence time for vapor disentrainment, and the venting process must be completed downstream of the column outlet. The vent-retum nozzles must always be located above the tray s liquid level. Downstream piping must be designed for self-venting flow (Fig. 4.5). 

The result states that the specific entropy in the tank remains constant at all times it is, therefore, equal to its value at the beginning of the venting process. This provides the additional equation for the integration of the energy balance equation. We return to eq. (6.7 ) and work on the derivative d(MU)/dM. First, we note that this derivative expresses changes in the tank that occur at constant specific entropy. 

The term set pressure is used to denote the pressure at which the relief device is open fully. This is not the definition used by some — for example, British Standards. For a safety valve the set pressure is often 10% above the set pressure as specified by the manufacturer or measured in the workshop, since this higher pressure is needed to open the valve fully. For a bursting disc, the set pressure is the nominal burst pressure plus any tolerance (or alternatively it is the maximum specified bursting pressure). The term overpressure is used here to mean the difference between the (redefined) set pressure and the maximum pressure reached during the venting process. 

The unconverted VCM is vented-off to a gas-holder or straight to a VCM recovery unit, before stripping operations. The objective is to reduce the pressure close to atmospheric. Because of the surfactants or emulsifiers present in PVC water mixture, the reactor contents are liable to foam during this venting process, especially in the emulsion process. This removal of unconverted monomer can be performed either in the polymerisation vessel itself, or in a blowdown tank. Some t5q)es of vessel will be equipped to catch any carry over, should it occur. 

If the leak is in the process system, shut the gas off at the source. Vent process gas to a scrubber and purge lines with dry inert gas before making permanent repairs. 

These flow resistance considerations are important to vacuum systems when through these, gas flows are restricted in connection with pump-down processes or venting processes or when measuring leaks, for example. 

Reaction forces on the equipment, induced by the venting process... 

Table 1 shows the hierarchical task analysis of P.TW system procedure in the studied petrochemical plant. As it can be seen, 11 main tasks and 4 subtasks were identified in HTA process. Task No. 3 (Inspecting the workplace and complete the checklist section in the permit) had 4 subtask including venting process equipments from flammable and toxic materials, lock out and tag out the electrical equipment, cleaning the work area from flammable material and isolation of process equipment. 

Venting process equipments from flammable and toxic materials... 

In order to check our understanding of the process, the temperature profiles shown in Fig. 5 were used to calculate the pressure decay in the venting operation of the flight tank. The decay in tank pressure was found to be a function of liquid temperature, vapor temperature, vaporization rate, ullage, and line and valve size. The calculated values, as well as the experimentally measured values, are shown in Fig. 6. The pressure dropped rapidly during the initial few seconds and then decreased at a much lower rate until the vent valve was closed. The pressure conditions in the tank with respect to the ambient pressure of about 3 psia (altitude 40,000 ft) caused the flow out of the tank to be choked (sonic velocity in the vent valve) during the entire venting process. 

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