Safety valve required capacity

[Gvdl]

Hey all,
I have a question about calculating the required capacity.

In like to discuss the following case:
A steam boiler has a rated capacity of 3.500kg/h. This delivers saturated steam (16barg) to a pressure vessel (8barg design) via a reducer DN100 to DN50.
How can i calculate the required capacity ?
Most calculations i found require velocity, which is unknown.
Frictional losses are negligible
Kind regards

 

[RVAmeche]

You're delivering 16 barg steam to a 8 barg vessel? Why...

API 521 and 520 provide guidance on evaluating potential credible scenarios (such as blocked outlet on your 8 barg vessel here) and determining the required orifice area, respectively.

 

[Gvdl]

You are correct, there is a pressure control valve in between. But in case o failure/misfunction the pressure in the vessel could still get to high. Excuses for the missing information.
I wil have a look for the api codes in the library,thanks you for the reply

 

[RVAmeche]

If there's no bypass around the regulator, that would be a control valve failure and you would take the Cv/trim of the regulator, the worst case upstream & downstream pressures, and determine the flow rate. Some regulators like Emerson have a "wide open flow rate" equation that you can simply plug in.

If there's a manual bypass, you should look at the max flow rate through that pipe & valve based on the same worst case pressures (worst case here resulting in maximum dP for max flow).

 

[MJCronin]

Any relief devices on this pressure vessel.... or adjoing piping ?

Is it an ASME vessel ?

If not, why not ?

MJCronin
Sr. Process Engineer