API 521 method

The metiiod presented in API 521 is mostly used in the sizing of KO drums. This method is based on the droplet settling velocity and does not calculate the K factor velocity. 

The value of the dimensionless drag coefficient Cp depends on the Reynolds number (C(Re) ), which is calculated as 

Process engineering and design using Visual Basic 

The vapor-flow area is calculated as tire area available above the high liquid-level shutdown. Once tire vapor-flow area is known, the vapor residence time can easily be calculated, using the actual vapor velocity. The required length of the KO drum is calculated by multiplying the droplet velocity and vapor residence time. This length is then checked with tire available length. 

Separation of two immiscible liquids is possible due to the difference in their densities. This general principle of liquid-liquid separation is applicable for both horizontal and vertical separators. Liquid-liquid separation is better achieved in a horizontal separator due to the larger interfacial area. 

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The separator design using the API 521 method has been developed only for the horizontal separator. 

The separator design using API 521 method uses a high-level shutdown (instead of normal liquid level, as in other cases) to calculate the separator length. 

The design method for sizing this type of system was published by Grossel 8 and in API 521.9 The method is based on the maximum allowable velocity for minimizing liquid entrainment. The dropout velocity of a particle in a stream is... 

In using the control valves standard (IEC 534-8-3, ISA-S75.17 or VDMA 24 422) to achieve more accuracy, we always encounter enormous difficulties. It impossible to ensure that using this method to calculate noise level is more accurate, or even as accurate, as simply using the API RP 521 method. 

This rate is higher than would be predicted by the API 520/521 method and, after an initial period, it may not be sustained. 

Thermal effect modeling is widely used in chemical plant design and CPQRA. Examples include the Canvey Study (Health Safety Executive, 1978,1981), Rijnmond Public Authority (1982) risk assessments, and LNG Federal Safety Standards (Department ofTransportation, 1980). The API 521 (1996a) method for flare safety otdusion 2ones is widely used in the layout of process plants. 

A flame under the influence of wind will tilt in the direction that the wind is blowing and will change the location of the flame center. API RP 521 (2007) presents two methods for estimating the required flare height when the flame is tilted. 

The following multi-step method may be used for calculating the required orifice area for SRVs on vessels containing liquids that are potentially exposed to fire. (Reference API Recommended Practice 521, Fourth Edition.)... 

As of today, the only internationally recognized method known to approximate the noise level caused by SRVs is described in the API RP 521. 

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. 

Design codes and standards such as API RP 521 and the DIERS Project Manual (Fisher et al., 1992) should be consulted for other correlations and recommended methods for calculating relief loads. The DIERS Project Manual also discusses calculation of relief loads for underpressure scenarios (Section 13.17.6). 

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