Process mode for the F1 example simulation

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

• Size relief valves based on the required flow rate 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). Confirm this by setting the Service parameter to InletPipe. 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 and select TailPipe for the Service 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 must confirm the sizing in Fluid Flow mode.

• Estimate the collection laterals 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.

• Model inlet pipes with the Incompressible flow equation. Model all other pipes with the Isothermal flow equation according to the API 520 recommended practice.

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