Correction factor for back

Correction factor for back pressure. Note for conventional safety... 

Kt, = vapor or gas flow correction factor for constant back pressures above critical pressure (see Figure 7-26). 

K = liquid correction factor for variable back pressures from Figure 7-28. Applies to balanced seal valves only. Conventional valves require no correction. 

To correct for the relatively small amount of decomposition of monosaccharides liberated under the conditions presented in Fig. 1, it is possible to subject a mixture of monosaccharides to identical conditions of hydrolysis and to measure the decomposition compared to that of a mixture not subjected to acid hydrolysis, in order to obtain a correction factor for losses by hydrolysis. Alternatively, in order to measure decomposition, hydrolysis may be continued for an extended period of time, and the concentration of monosaccharide may be extrapolated back to time zero. 

Figure A8.6 BACK PRESSURE CORRECTION. FACTOR (FOR NON-CHOKED FLOW)...

In Figure A8.6, the correction factor for non-choked flow is plotted against the dimensionless back pressure (1-ti)/(1-t c), where t is the. actual available pressure ratio (see above) and v[c is the critical pressure ratio. For flow in which friction is not significant, r c can be read from Figure A8.2. t. . . ... 

A batch record, as stored in the database, is represented by a collection of different data on the actual production procedure and the current production enviromnent. Back in 1994, at the point of decision, the data available electronically were stored in several databases. Database update was time-consuming and difficult data analysis even needed different program interfaces. Therefore, the database for the new system had to be a central, uniform database for the whole production plant.The bill of material is fed from ERP as well as general planning. LIMS is another interface for the input of analytical data that is important in the calculation of correction factors for the content of API. 

In the case of a balanced-bellows relief valve, the impact of general back pressure depends on the percentage of overpressure and is known as the back-pressure correction factor. For 10% overpressure, the back-pressure correction factor is 1 up to 30% general back pressure. For 16% overpressure, the correction factor does not change (value = 1) up to 37% back pressure, and for 21% overpressure, fhe correction factor does not change (value = 1) up to 50% back pressure. 

Balanced-bellows PRVs can be used for higher back pressme up to 50% back pressure without reducing the back-pressure correction factor (for a 21% overpressure situation). 

Figure 17. Variable or constant back pressure sizing factor, Kw for 25% overpressure on balanced bellows safety relief valves (liquids only). The curve represents conqiromise of the valves reconunended by a number of relief valve manufacturers. This curve may be used wiien the make of dw valve is not known. When the make is known, the manufacturer should be consulted for the correction factor.

In the case of a balanced bellows pressure relief valve, to the maximum pressure permitted by considerations of bellows and bellows bonnet flange mechanical strength. This maximum pressure may be obtained by applying the following correction factor to the maximum back pressure listed for 38 °C. 

All relief valves are affected by reaching critical flow, which corre-spond.s to a back-pressure of about 50% of the set pressure. Pilot-operated relief valves can handle up to 50% back-pressure without any significant effect on valve capacity. Back-pressure correction factors can be obtained from the relief valve manufacturers for back-pre.ssures above 50%. API RP 520 gives a generic method for sizing a pilot-operated relief valve for sub-critical flow. 

Note The curves above represent a compromise of the values recommended by a number of relief valve manufacturers and may be used when the make of the valve or the actual critical f ow pressure point for the vapor or gas is unknown. When the make is known, the manufacturer should be consulted tor the correction factor. These curves are for set pressures of 50 pounds per square inch gauge and above. They are limited to back-pressure below critical flow pressure for a given set pressure. For subcntical flow back-pressures below 50 pounds per square inch gauge, the rnanufacturer must be consulted tor values of Kk. 

Calculations of Orifice Flow Area using Pressure Relieving Balanced Bellows Valves, with Variable or Constant Back Pressure. Must be used when backpressure variation exceeds 10% of the set pressure of the valve. Flow may be critical or non-critical for balanced valves. All orifice areas. A, in sq in. [68]. The sizing procedure is the same as for conventional valves listed above (Equations 7-10 ff), but uses equations given below incorporating the correction factors K, and K,, . With variable backpressure, use maximum value for P9 [33a, 68]. 

Data are available back to 1963 from the downtown San Bernardino station operated by the county Air Pollution Control District (apcd). The colorimetric potassium io de method used to measure total oxidants was calibrated according to the method of the California Air Resources Board. A positive correction factor of 1.22 was used to adjust mountain data for the decreased air pressure at the higher elevation. 

All correction factors such as tunneling, back-crossing of the barrier, and solvent frictional effects are captured by K, which is between 0.1 and 1 for the reactions in solution in question here. The equilibrium constant K is expressed by partition functions, where the mode normal to the reaction coordinate v is approximated by the term kBT/hv. In the resulting Eq. (2.5), v cancels out. 

For preliminary estimates, the coefficient Kj can be taken as 0.975 for a relief valve and 0.62 for a bursting disk. The back-pressure correction factor, Ky, can initially be assumed to be 1.0 for critical flow. The combination correction factor, K, is used when a rupture disk is used upstream of the relief valve (see next section), in which case it is 0.9. If no rupture disk is used, then is 1.0. For vessels designed in accordance with AS ME BPV Code Sec. VIII, Pj = 1.1 times the maximum allowable working pressure. 

The important point that arises from the Rodger-Sceats reduction is that the dynamics can take place on an effective potential P defined by Eq. (2.19). The origin of the potential can be traced back to the requirement that at long times the system must achieve a thermal distribution which is consistent with a Boltzmann distribution on the full potential and the use of P simply ensures that the partition functions of the system will be given correctly. This will be very important in applications to chemical reactions, because the partition function plays an important role in determining Arrhenius activation parameters. The dependence of P on the reaction coordinate simply accounts for this effect. For example, the reactant and transition state configurations are defined by the minima and maxima of P at qi and gj, and the Boltzmann factor for activation is... 

Sources of error can be introduced in each conversion from volume to moles and back to weight, although for simple examples such as the one above it does not really matter which method of calculation is employed as long as the correct answer for the purity of citric acid is obtained. However, for more complicated calculations, involving the use of back and blank titrations, this author believes that factors and equivalents simplify volumetric analysis and they will be used for that reason (rather than any reason of dogma) in the remainder of this book. 

Consider now the barrier crossing problem in the barrier controlled regime discussed in Section 14.4.3. The result, the rate expressions (14.73) and (14.74), as well as its non-Markovian generalization in which cor is replaced by k ofEq. (14.90), has the structure of a corrected TST rate. TST is exact, and the correction factor becomes 1, if all traj ectories that traverse the barrier top along the reaction coordinate (x ofEq. (14.39)) proceed to a well-defined product state without recrossing back. Crossing back is easily visualized as caused by collisions with solvent atoms, for example, by solvent-induced friction. 

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