Valve selection 1

[DiegoMartinez]

People,
I want to use a 3" Class 1500 Globe valve on the following service:

80% Co2 - 20% Methane
Design Pressure: 150 Barg
Design temperature: -10C to 120C
Onshore application

If I want to use SS trim and body, the valve would be very expensive; however I know my best bet is to use 316 for internals only. Any suggestion on what body material to use to reduce cost?

Rgds Diego

 

[terje61]

Hello Diego,

I use the following rules:

In case there is no H2O present: carbon steel
In case of H2O and partial pressures below 0.2 bar: Carbon steel
In case of H2O and partial pressures below 138 bar: 13%Cr. steel
In case of H2O and partial pressures above 138 bar: 316SS or preferably DuplexSS

In your case the partial pressure is 151 bara x 80% = 121 bara. So assuming you have water present a 13%Cr steel would be sufficient e.g. ASTM A487 Gr. CA6NM Cl.B

Regards,
Terje

 

[JimCasey]

Diego, Will you be isolating (on-off) or throttling with this valve? If throttling, what downstream pressure to you expect? You may need some really hard alloys to withstand the noise and velocity if this is a throttling valve. Maybe even a choke....

 

[DiegoMartinez]

Thanks Guys,

The service is saturated Co2 and I am wondering if I can use A216 WCB body and 316SS Trim except Seat ring with Stellite overlay over Carbon Steel.

I am aware of the noise but it would not be operated regularly.

Rgds Diego

 

[UNSR60001]

Diego:

As far as the Temperature-pressure goes you are fine with ether carbon Steel or 316SS in a class 1500# valve. What you need to consider is the Corrosion Tables and they are as follows:

Carbon dioxide, dry: Carbon Steel or 316SS "good"
Carbon dioxide, wet: Carbon Steel "not recomended" 316 "good"
Methane : Carbon Steel or 316 are "good"

My recomerndation is as follows:

Carbon steel valve with Stellite 6 Full hard face on body and disc and 13%Cr steam (no 316 needed)

Stainless Steel Valve with Stellite 6 Full hard face body and disc 316 steam.

For this pressure what you must consider is that you need hard face seat in stellite 6. Do not use 316 as seat material as it does not perform well in high pressure applications. 13% seats translate into marginally lower cost savings on this size valve so don't even bother with it.

Lastly, if you are being told that a 316SS valve is so much more expensive than a Carbon Steel. Or for that mater you get the same story for Stellite seats, let me know and I would be very happy to recommend you a supplier that would have this valves in stock at a reasonable price.

 

[DiegoMartinez]

Thanks UNSR,
I thought about getting the following valve:

3" cLASS 1500 gLOBE, rf, bODY: a351 CF8M, Trim: A182 316 SS with Stellite Overlay.

However, I'd assume the worse case scenario that the service is wet Co2. Now are you suggesting the following valve:

A216 WCB, with Stellite overlay. What is the trim material?

I am in Australia. I would be glad if you can let me know this supplier.

Rgds Diego

 

[DiegoMartinez]

UN:
Please could you say how much the carbon steel valve with Stellite overlay cost?
However my preference is to choose the valve I mentioned above.

Rgds Diego

 

[UNSR60001]

Diego:

What I am saying is that if you have WET CARBON DIOXIDE, carbon steel is not recommended for this service.

your valve selection of " 3" cLASS 1500 gLOBE, rf, bODY: a351 CF8M, Trim: A182 316 SS with Stellite Overlay " is apropriate for Wet Co2.

should your service be DRY Co2 you can use a WCB valve. when i mentioned above 13%Cr. stem it would be the same as 410SS trim . Remember you need the stellite 6 FULL HARD FACE.

As far as a supplier goes. Unfortunatly I am in the USA and the suppliers that I can recommend you with are in America. Shipping would not be cost effective on this order.

Let me know if I can be of further help.