Supply pressure as % of set for dome pressure recovery[3 1

[gguliye]

Dear Team,
What does the marked parameter mean? It is the picture from crosby 93 manual
regards,

 

[The Obturator]

It is referring to the percentage of set pressure required, on top of the dome, to start to close the main valve.

Is this Crosby? They never had such low pressure pilots - can you please copy the front of this publication.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[gguliye]

it is crosby, 93 IOM

https://www.emerson.com/documents/a...s-93-iom-anderson-greenwood-us-en-5197270.pdf

 

[The Obturator]

Anderson Greenwood not Crosby.

Earlier comments regarding pressure apply when the dome is being pressurised after the main valve opens, the pilot valve is said is said to be "hunting" for the closing pressure.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[gguliye]

Valve man,
again u are right sorry
so it means for the snap action if the valve is open at 1 psig, the valve dome will be fully closed once the dome pressure reaches 0.9 psig.
could u please confirm??
2) could u please confirm when we need the guide with the sponge seat? in very low pressures to add additional weight on sponge for bettter sealing??
3) in large sizes we always use deflector?? 8" 10" 12"
4) we have 2 kinds of pilots available medium > 15 psig and low <15 psig?
regards,

 

[The Obturator]

Hi again.
1) Not quite - the IOM is referring to the pilot valve adjustment rather than the main valve. There would be a little interaction between the pilot and main valve. A snap acting with set 1 PSIG should have the pilot valve adjusted to give at least 90% of dome pressure recovery to close the main valve (minimum start to close pressure). It is not stated what this will actually be at the main valve.
2) Actual pressure is not advised - see 2.1 of the IOM (factory would advise acc to application).
3) Yes.
4) Yes.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[gguliye]

Thank u sir