Fauskes method

Once it has been checked that1 the method is applicable (see above), it can be used for relief system sizing. Fauske s method is14,51 - 

FRICTIONAL CORRECTION FACTORS FOR USE WITH FAUSKE S METHOD.  

A worked example of the use of Fauske s method for relief sizing is given below. 

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It is reeommended that a safety faetor of at least 2.0 be used [34]. In eertain eases, lower safety faetors may be employed. The designer should eonsult the appropriate proeess safety seetion in the engineering department for adviee. Table 12-4 lists the applieability of both Leung and Fauske s methods. 

If Fauske s method yields a signifieantly different vent size, then the ealeulation should be reviewed. 

The answer obtained from the Leung s method should not be signifieantly smaller than that of Fauske s method. 

There is no standardized method for predicting or controlling runaw ay reaction that may lead to explosions (deflagrations or detonations), except possibly the Fauske approach (Figure 7-61). 

Fauske and Associates, Inc., Flashing Viscous Flow of Polystyrene Mixtures Test Data and Scale-Up Methods, FAI/ 89-26, April 1989. 

Grolmes, M. A., Leung, J. C. and Fauske, H. K, A Review of Simplified Multiphase Flow Methods for Emergency Relief Calculations, Paper Presented at the AIChE 1990 Spring National Meeting, Orlando, FL, March 18-22, 1990. 

Experimental data can be obtained from the DSC and from reaction calorimeters for the conditions of the desired reactions, and from the DSC, the ARC, the Reactive System Screening Test (RSST—Fauske and Associates) and from the Vent Size Package (VSP) for conditions allowing undesired reactions. The pressure effect can be studied using the ARC or DIERS methods. From the results of these tests, the rate of temperature rise and the maximum acceptable conditions for specific equipment can be calculated. The same holds for the pressure rise rate. 

Fauske s method for vapour pressure systems (see A5 3) and-the sizing method for gassy systems (see Chapter 7) have been, used to do a very.approximate relief sizing. Alternatively for screening purposes, nomographs153 could be used. "... 

For case (ii), Fauske s method (assuming homogeneous venting) is ... 

The version of the ERM given. by equation (9.4) is used in Fauske s relief sizing method (see A5.3), together with a correction factor for friction if relief is via a bursting disc. Such correction factors are discussed further in 9.6.1. 

Fauske s method14,51 (given below) is based on emptying the reactor (or achieving vapour/ liquid disengagement) before the pressure has risen from the relief pressure to the maximum accumulated pressure in a vented system. The method incorporates the simplified equilibrium rate model, ERM, for saturated liquid inlet (see 9.4.2) together with the Clausius-Clapeyron relationship (discussed in 6.3.3). The method makes use of adiabatic experimental rate data for the runaway, whose measurement is described in Annex 2. 

The version of Fauske s method given in A5.3.2 below is simplified by assuming that two-phase relief occurs until the reactor is empty (a safe assumption for vapour pressure systems). This makes the results directly comparable with those from Leung s method (in 6.3). The full version of Fauske s method14,51 allows account to be taken of vapour/ liquid disengagement before the vessel has emptied. This method is given in A5.3.4 below. 

Fauske s method has the stated condition of applicability that the absolute... 

As the safety valve has a de-rated discharge coefficient of 0.87, then A=0.0383/0.87 = 0.044 m2. In this case, Fauske s method gives a slightly higher relief area than the 0.0378 m2 given by Leung s method. 

This method extends Fauske s method14,51 (see A5.3.2) to cases in which the system is not inherently foamy and so vapour/ liquid disengagement will occur before the reactor js empty. 

A5.3.5 Worked example of Fauske s method with disengagement... 

Fauske[20,21] has produced nomographs (graphs) for the purpose of relief sizing. That for tempered systems is based on Fauske s sizing method for vapour pressure... 

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