Overpressure period

The overpressure period in the reactor building is very short, of the order of a couple of minutes, so the design pressure is reduced and the design leak-rate can be increased relative to single unit containment. 

Co-distillation leads to long period of time under heat resulting in exceeding the isothermal aging characteristics for a thermally unstable material which leads to thermal decomposition and overpressure of the vessel. 

Car-Sealed Closed Valve - In certain cases it may be advantageous to use car sealed closed valves, such as in a bypass around a fuel gas control valve used for furnace flameout protection. The bypass is provided so that the automatic shutdown system can be periodically checked for operation. Where CSC valves are used for other purposes, they are also limited to appUcations where inadvertent opening of the CSC valve would not overpressure the equipment by more than 1.5 times design pressure. 

Galloping Detonation A detonation that periodically fails and reinitiates during propagation. This type of detonation is typically observed in near-limit mixtures. Since it reinitiates via DDT, a galloping detonation is periodically overdriven and results in large overpressures at periodic distances along a pipe. 

Room overpressure can conveniently be tested during this period. Produce a single line sketch of the conditioned space(s) including doorways. Test for air-flow direction with hand smoke tubes, both at the top and bottom of closed doors, and record the direction of flow. Crack the doors open if fully sealed. 

Pyruvic acid is not stable at ambient temperature when it is stored for a long period of time. It can only be stored in a refrigerated room. A bottle of this acid was stored in a laboratory at 25°C and detonated, probably because of the overpressure created by the formation of carbon dioxide. Indeed, with diacids and complex acids the decomposition is made by decarboxylation. In this particular case, this decomposition should give rise to acetaldehyde. It could be asked whether, in the exothermic conditions of this decomposition, a polymerisation of this aldehyde (see Aldehydes-ketones on p.310) did not make the situation worse. 

The pressures on the sides and roof of the structure build up to the incident overpressure as the blast wave traverses the structure. Traveling behind the blast wave front there is a short period of low pressure caused by a vortex formed at the front edge during the diffraction process (Figures A. 8c and A. 9c). After the vortex has passed, the pressure returns essentially to that in the incident blast wave. The air flow causes some reduction in the loading to the sides and roof, because the drag pressure has a negative value for these surfaces. 

Although the curves in Figures 13-15 were developed for transient loads defined by total applied forces and inpulses, we could as easily have developed them by initially specifying an applied pressure transient loading, with its accompanying specific impulse, plus a loaded area. So, the concept certainly applies to simple structures under blast loading. The inportant inferences to be drawn from the simple- analyses are that structures respond primarily to peak overpressure if their vibration periods are much shorter than the blast duration, while they respond primarily to specific impulse if their vibration periods are much longer than the blast duration. 

The effect of a detonation depends on the shock wave, that is, an immediate peak overpressure followed by a longer period with an underpressure. The strength of the shock wave depends on the mass of the detonating materials. Detonations are mostly induced by initiation sources. In some cases, a deflagration may make a transition into a detonation. Working with chemicals and systems under plant conditions where a detonation can be induced is NOT recommended. Whether or not a chemical or chemical system can detonate can be determined only by specific tests as outlined in Chapter 2. 

This is a very particular application where we have the potential for overpressure due to loss of overhead condensing or reflux failure. In the event the cooling medium in the condenser is lost, additional vapour may be present at the top of the column. This additional vapour may require pressure relief. In a typical distillation system, a cooling failure also results in a loss of reflux within a short period of time (typically about 15 minutes). API RP 521 states that the required relief rates before and after loss of reflux should be considered. The Berwanger audit method encompassed both of these calculations, as it was not intuitive, which case would require the larger required relief rate. 

Stirring, 6.3 ml (5.3 g, 41 mmoles) of ethoxydiethylaluminum(III) in 30 ml of diethyl ether is added from the dropping funnel over a 15-min period. The resulting reaction mixture is then stirred for 24 hr at room temperature while it is kept saturated with ethylene. The reaction mixture is then cooled again to 0° for 2 hr (stirring is continued) to complete crystallization. By means of a siphon and a slight overpressure of argon, the contents of the flask are transferred onto a frit cooled to 0°, as depicted in Fig. 13. The precipitate is... 

Autoclaving with steam involves time/temperature relationships, i.e. 134°C for 3 min or 121°C for 15 min or 115°C for 30 min or such combinations of temperature and time which ensure sterilisation. It is advisable to carry out autoclave tests on any plastic as part of the development programme. Now that autoclaves have balanced or overpressure facilities, experiments have to be carried out in order that the correct conditions can be selected. It should be noted that distortion or extension (initially due to internal pressure in the pack) is likely to occur during the cooling cycle and it is during this period that additional pressure is required to overcome the internal pressure. 

Such dynamic overpressure systems (sic.) with traps experiencing cyclic fill-drain periods was proposed by Leonard (1993) and invokes intermittent breaching of the seal and subsequent annealing due to petroleum column loss, progressive burial and diagenetic cementation. 

In the intermediate stage of a fast deflagration, the peak overpressure is not so high, but the pressure drop is over a larger time period making the impulse, i.e., the integral of pressure over time, which is a measure for the load on a building structure, about the same in both cases [12]. 

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