Relief set pressure

Tr = temperature of reactants at relief set pressure To = aUowable temperature following complete quench To = initial temperature of the quen fluid = specific heat of the quench fluid Cr = specific heat of the reac tants (consistent Enghsh or SI units)... 

It is the rate of temperature inerease (i.e., power output) between the set pressure and the maximum allowable pressure, whieh determines the vent size and not the peak rate. Boiling is attained before potential gaseous deeomposition (i.e., the heat of reaetion is removed by the latent heat of vaporization). The reaetion is tempered, and the total pressure in the reaetor is equal to the vapor pressure. The prineipal parameter determining the vent size is the rate of the temperature rise at the relief set pressure. 

Fauske [32] represented a nomograph for tempered reaetions as shown in Figure 12-35. This aeeounts for turbulent flashing flow and requires information about the rate of temperature rise at the relief set pressure. This approaeh also aeeounts for vapor disengagement and frietional effeets ineluding laminar and turbulent flow eonditions. For turbulent flow, the vent area is... 

Blowdown The pressure difference between the relief set pressure and the relief reseating pressure. It is expressed as a percentage of the set pressure. 

On spring-operated valves the adjustable spring tension offsets the inlet pressure. The relief set pressure is usually specified at 10% above the normal operating pressure. To avoid the possibility of an unauthorized person changing this setting, the adjustable screw is covered with a threaded cap. 

Rupture discs are specially designed to rupture at a specified relief set pressure. They usually consist of a calibrated sheet of metal designed to rupture at a well-specified pressure. They are used alone, in series, or in parallel to spring-loaded relief devices. They can be made from a variety of materials, including exotic corrosion-resistant materials. 

The problem is to evaluate the relief size required. The relief set pressure will be 8 barg. 

Tr Temperature of reactants at relief set pressure SWEPT BEND ... 

G - vent flow capacity per unit area at relief set pressure (kg/nrs) q - heat evolution rate per unit mass (W/kg)... 

An easy way to obtain substance data is to look at the organic solvents which are expected to be used. In many cases a selection can be made containing those which cover the operational range by their boiling points under standard pressure and at the maximum relief set pressure. Figure 7-6 shows such a selection for the example used to help understand the presented procedure. 

A nomogram has also been produced, relating the volumetric gas generation rate to the ideal vent area for differing relief set pressures, which provides a preliminary indication of the required vent area . ... 

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