VALVE MATERIAL for Demineralized WATER 1

[ALEXANDRAHARPER]

I NEED TO KNOW WHICH MATERIAL IS THE ADECUATED FOR DEMINERALIZED WATER AND SUPERHEATED STEAM IN CHECK AND GATE VALVES.

THE PRESSURE IS 565 PSIG AND 333° F

WHICH KIND OF GATE VALVE IS ADECUATED FOR DEMINERALIZED WATER AND SUPER HEATED STEAM????

 

[gsxra]

As for demineralized water I would use SA-351-CF8M (316SS), ANSI 600. For conditions given you are saturated water so I don't know what mat'l and pressure class to recommend for SH steam.

As for what type of gate valve, there are many manufacturers but I have had alot of sucess with HP Valves out of the Netherlands.

 

[marklobo]

We have experienced severe erosion damage to control valve trim in demineralized water service. We've tried tungsten carbide with cobalt-, nickel-, and even a proprietary ceramic-binder.

Before I start a new thread on this subject, what is known about wear-resistance materials for surfaces subjected to demin water at high fluid velocities?

 

[Ashereng]

marklobo,

I didn't realise that demineralised water was more erosive than "normal water"? What is it in demineralised water that causes additional erosion?


ALEXANDRAHARPER,

Are you looking for a gate valve in superheated steam service to do shutoff service? What leakage class do you need? Are you thinking of a slab gate (conduit gate some people also call them) vs a traditional knife gate? For good shutoff, I would go slab gate.

 

[pennpoint]

Ashereng
It's not whats in demineralized water, it's whats not in it.
"ALEXANDRAHARPER" may be in the deionized area of water processing/treatment, and this can cause a bunch of problems. Ion starved water will corrode stainless steel easily. One has to know the level of resistivity when designing for deionized water systems.
Alexander must be sure of the resistivity of the water and other factors to really determine whats going on.

pennpoint

Best regards
pennpoint

 

[Ashereng]

Hi pennpoint,

What you are saying is that this is a "corrosion" issue.

We have experienced severe erosion damage to control valve trim in demineralized water service...

...what is known about wear-resistance materials for surfaces subjected to demin water at high fluid velocities?
[/quoter]

marklobo stated in his post that it was an "erosion" issue. I was just trying to clarify for my own edification.

 

[joeswoes]

If the problem is corrosion of thes.s., why not composite valves ?

 

[JimCasey]

Demin water has nothing in it that is dissolved to saturation. Therefore almost anything is soluble in it. Imagin the crusty old engineer telling me: "Boy, it's HUNGRY for minerals"
Typically 300-series stainless steels are the material of choice for demin/DI water services. This application (565psi@333F) is out of the reach of a TFE-Lined valve, but that would be a good choice at gentler temps and pressures.

Marklobo: If tungsten carbide parts are being eroded, I suggest you should take a serious look at your velocity and trim design. Basic anticavitation trim >CONTAINS< cavitation, managing the bubbles so that they implode where they wil not cause damage. Severe-service anticavitation trims such as the Valtek Channelstream, CCI Drag, Masoneilan VRT and others all manage the velocity of the flow so that the fluid pressure never drops to the vapor pressure so cavitation will not happen. Velocity-control trim would seem to be indicated for your application.

 

[pennpoint]

Ashereng
02/01/06
What I am saying is: common everyday water (H2O) is fine for us humanoids to drink, cook with, shower/bathe, and water our lawns, et al.
But once you start altering the physics of H2O you start to see problems.
Most water we are confronted with is very neutral pH wise, but when you start removing ions it gets a little wierd and aggressive and wants those ions back. If your system is designed beyond a purity level than it needs to be, you might be in the deionization zone of water purity.
I suggest you spit or piss in it. one of the two will neutralize the its deleterious effects.

Regards
pennpoint

Best regards
pennpoint

 

[mk3223]

ALEXANDRAHARPER,
It sounds that the demineralized water of 565psig and 333F had been deaeratored and pumped through the boiler feed water pump.
if it is ture, the material of the piping and valves could be carbon steel. Typically, 316SS material is used before get into deaerator.

in this case, for high presure deaeratored water and super heated steam (say 500psig), the carbon steel valve body with 12 Cr trim and hard faced seat/disc could be used.

For the erosion problem in control valve as stated in "marklobo" note, it may be because the valve was undersized, so the high water flow through the valve seat to create high pressure drop and cavitate the valve trim.