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Restriction orifice

Allgemeine Diskussion » Restriction orifice Posted: 31. Mai 2023 - 1:57


I am using CONVAL 11.4.1. I am using restriction orifice sizing. I have question about Safety-related application. 

When should I check safety related application?

Very often, If I check safety related application, the calculation will show errors.

Thank you


Benedict Nowak

Bild des Benutzers Benedict Nowak


Posted: 31.05.2023 - 9:59


Hello Bin Zhang,

The safety related application function should be used to calculate a maximum theoretical flow.
See the following excerpt from the CONVAL help.

  • For safety related applications, e.g. orifice plates which are limiting the upstream mass flow of safety valves, the modifiers xT respectively FL2 are set to one, in order to calculate the theoretical maximum flow at critical conditions.

    Use this option if you want to ensure that the calculated flow is never exceeded.

If this function is active, no limitation of the flow (due to chocked flow) occurs. So that a higher (only theoretical) flow is possible. 

This can also be seen in the following graph. The "kink" in the blue graph shows the point at which chocked flow occurs and an increase in differential pressure does not cause a further increase in mass flow rate. The orange graph shows the curve of the mass flow with active safety related application.​


Let me know if you have any other questions.


B. Nowak
CONVAL Support