Orifice or flow indicitor at the air purge connection line 1

[knapee]

Dear eng-tips members.

A air purge connection detail(attached in the post).
The compressed air(nitrogen or hydrogen gas) sweep the tube through the nozzle to the reactor.

What is the difference if FI( flow indicator) is replace by the RO
(restriction orifice)?
And how to size the flow rate for this kind of purge line?

Thank you very much.

 

[hacksaw]

you've sort of answered the question you've asked...

the flows are generally not known other than something is required, the FI is usually fitted with a needle valve,

 

[Pumpsonly]

An RO has a totally different function from a FI.

FI is to provide visual indication of the air /gas is flowing.

An RO is a device to restrict flow rate calculated based on the know up stream and down stream condition.
You already has a PCV in the purge line which will control the flow rate of the gas. The required flow rate will depends on the volume of the equipment you need to purge and it down stream pressure.