Process mode for the F2 example simulation

The purpose of Process mode is to size the relief valves and provide initial pipe sizes. If this is an existing system and you already know the sizes, enter the known pipe sizes. For new systems:

• Size the relief valves based on a required flow by selecting an orifice letter so that the required area is less than the calculated area.

• Size the relief valve inlet pipes such that the pressure drop is less than 3% of the set pressure (SP) of the relief valve at the rated flow to prevent relief valve chatter (3% rule). For sizing, set the inlet pipes to use the rated capacity flow for the relief valve by selecting RatedCapacity for the Design Basis parameter.

• Estimate the relief valve tail pipe sizes assuming that they have 10% back pressure (for conventional valves) at rated flow. For sizing, set the tail pipe to use the rated capacity flow for the relief valve by selecting RatedCapacity for the Design Basis parameter. Since back pressure depends on the pressure drop in the common headers from other relief valves, this calculation is only an estimate and you much confirm the sizing in Fluid Flow mode.

• Estimate the common collection header pipe sizes at the required flow rate and on a velocity or pressure drop sizing criteria. Since back pressure depends on the pressure drop in the common headers from other relief valves, this calculation is only an estimate and you must confirm the sizing in Fluid Flow mode.

• Set the FlowModel parameter for the inlet pipes to the Incompressible flow equation. Set the FlowModel parameter for all other pipes to the Isothermal flow equation according to the API 521 recommended practice.

• Specify the flare gas flow, pressures, and temperatures at each source to determine the initial pressure profile for Fluid Flow mode.