Relief valve opening

A common cause of a BLE T] in plants of the hydrocarbon-chemical industry is exposure to fire. With an external fire below the liquid level in a vessel, the heat of vaporization provides a heat sink, as with a teakettle evolved vapors exit tnrough the relief valve. But if the flame impinges on the vessel above the liquid level, the metal will weaken and may cause the vessel to rupture suddenly, even with the relief valve open. The explosive energy for a BLE T] comes from superheat. This energy is at a maximum at the superheat hmit temperature. (SLT is the maximum temperature to which a hquid can be heated before homogeneous nucleation occurs with explosive vaporization of the hquid and accompanying overpressure.) The SLT... 

Built-up Back Pressure - Is the frictional pressure drop that develops as a result of flow through the discharge system after the pressure relief valve opens. 

Figure 40.42 shows a flow diagram in a manifold that provides both pressure and return passages. One common line provides pressurized fluid to the manifold, which distributes the fluid to any one of five outlet ports. The return side of the manifold is similar in design. This manifold is provided with a relief valve, which is connected to the pressure and return passages. In the event of excessive pressure, the relief valve opens and allows the fluid to flow from the pressure side of the manifold to the return side. 

Correlations are needed to predict whether two-phase flow will occur after vapor venting is initiated by rupture disc failure or relief valve opening. Research is needed in this area, but for the present we recommend the following correlations to predict batch swell. For systems with low viscosity (less than 500 cp) an equation based on bubble column hold-up is used to obtain a swell ratio ... 

Chlorine flow to environment Internal relief valve sticks open Both internal pressure valves fail open and relief valve opens Operation Potential low chlorine flow to Tower Water Basin -see above Chlorine released to environment - potential personnel injury due to exposure Distinctive odor Pressure check valve located outdoors -unlikely to accumulate significant concentration III Action Item Consider venting relief valve above ground level... 

When froth is discharged (curve B in Figure 8-2), the pressure continues to rise as the relief valve opens. The incremental pressure increase over the initial relief pressure is called overpressure. 

What if the relief valve opens below its set pressure ... 

What if a reactor s relief valve open inadvertently ... 

When the relief valve opens, it allows vapor to discharge at a flow rate w kg/s. The number of moles of vapor in the vessel is then given by... 

Both internal pressure valves fail open and relief valve opens... 

Mechanical safeguards An overflow pipe near the top of the tank directs spill to a safe location The pressure safety relief valve opens... 

This type of filtration commonfy occurs when an efficient positive displacement punq> is used to feed a pressure fiber. Hie pump delivers a mfiform volume of slurry into fiie filter hence the filtration rate remains constant when filtering an incompressible material In order to achieve this constant rate the pressure delivered by the pun must rise, to overcome the increasing resistance to filtration caused by cake deporidon. It is usual for such a pumping system to include a pressure relief valve if the filtration cycle is long enou the constant rate period wffl.h,t followed by a constant pressure period after the pressure relief valve opens. ... 

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