Can the same PSV be used in water and nitrogen 2

[SrChemE]

Hello,
I received a request to verify if a Farris valve (27DA23-M20), which is currently used in water service can be used in nitrogen service. Would this be possible?
Thank you

 

[met11]

Yes, the Farris 2700 can be used for both. The difference is in the discharge coefficient K used for sizing. For air/gas/steam it's 0.878, for water it's 0.676. The nameplate can only be stamped with a capacity for one service though, so yours would be stamped with a liquid capacity.

Some valves are not designed for both services, and you have to de-rate the discharge coefficient using Figure 38 in API 520 Part 1. The trims are designed differently for vapor and liquid service.

 

[EmmanuelTop]

See page 2 (Introduction) and pages 8 and 9 of

http://www.cw-valvegroup.com/getatt...c-a26b6b18eb64/2700Series_PRV_Catalog_197C_R5

Dejan IVANOVIC
Process Engineer, MSChE

 

[SrChemE]

Thanks Mett11 and EmmanuelTop for your help.

The valve will most likely react differently on air and on water. So they are not interchangeable between the services because they will react differently on each service and the ASME nameplate will reflect the set and service the valve is being used on. Good to know.

Thank You both! Greatly appreciated.

 

[met11]

SrChemE, yes they will react differently, but whether you ordered it for water service or you ordered it for nitrogen service, it would be the same valve. They would only change how they bench test it, and what they would stamp on the nameplate. From the Farris 2700 catalogue that Dejan linked to:

"A single design handles air, steam, vapor and liquid services."

Hope this helps!

 

[SrChemE]

Is it a code violation to have water service valve with a SCFM stamped nameplate?

 

[EmmanuelTop]

It makes absolutely no sense to use SCFM unit for relief valve in liquid service. The same valve should be re-stamped with capacity in GPM units, according to liquid capacity tables shown on page 8 of the vendor catalog. The bench test procedure would also be changed, as met11 said.

You should be able to obtain the liquid service stamp from the supplier, without the need to change the valve. There are no reasons for changing the valve, if meets the required liquid relief capacity.

Dejan IVANOVIC
Process Engineer, MSChE

 

[SrChemE]

Thank you all for the help and clarification.

 

[JAlton]

CAUTION: When PRVs certified for Steam. Air & Liquid are assembled, there is a Spring Selection Process. Spring Charts for Liquid Service PRVs are not the same as Spring Charts for Air/Gas. To be specific, a Farris 27DA23-M20 Set for 100 psi Air would use a #C3033 with a range of 100-121 psi. That same spring in Liquid Service would have a range of 141-160 psi. Therefore, if you place a the Air Service PRV directly into Liquid Service at 100 psi, the Spring is 4 ranges too heavy. Your Overpressure Protection will not provide adequate capacity. On the other hand, placing a 100 psi Liquid Service 27DA23 directly into Air Service will give you an Air PRV with a weak spring that does not even show up on the OEM Air/Gas Chart. The PRV may leak and will definitely have performance problems because the spring may be compressed to solid height during a lift, which can damage other internal parts. Be careful.

JAC

 

[SrChemE]

JAlton, manu thanks for your comments and recommendation.
Much appreciated.

 

[e43u8]

JAlton,

I think your statement might should be corrected as follows:

"Therefore, if you place a the AirLiquid Service PRV directly into LiquidAir Service at 100 psi, the Spring is 4 ranges too heavy. Your Overpressure Protection will not provide adequate capacity. On the other hand, placing a 100 psi LiquidAir Service 27DA23 directly into AirLiquid Service will give you an Air PRV with a weak spring that does not even show up on the OEM Air/Gas Chart."

Am I wrong?