Using valve in place of orifice 1

[MattNCSU03]

I have been tasked with specifying a valve to replace an orifice that the client has been unable to properly size after several calculations and attempts. The orifice is a 7/32" plug-resistant orifice in a 1" line that is a bypass around a 3" extraction steam line drain AOV to a condenser at vacuum. The idea is that an operator can set the bypass valve such that the 3" AOV only cycles less than once per shift and should the AOV start to cycle more frequently, the bypass valve can be adjusted to eliminate the cycling. The existing orifice sizing calc says the orifice passes approx 1,500 lb/hr of condensate with the design upstream pressure of 273 psia and design outlet of 1.7 psia, temp 409F.

I have asked Fisher to specify a globe valve for this and Valve Technologies to specify a metal-seated ball valve for a normal flow of 2,000 lb/hr and max of 5,000 lb/hr and they have done that but having little experience with valves in this type of service, I'm not sure what the best choice would be in terms of longevity and ability to control flow and would appreciate any input. I already suggested upsizing the orifice again but that didn't go over well.

Fisher:
1" EZ Globe made w/ WC9 steel body, ANSI 600# SW ends, flow down, Equal pct characteristic, unbalanced, 316 plug

Valve Technologies:
Valvtechnologies # C5L12SA2SA0A Metal Seated Ball Valve, ANSI 300# Class, A182-F22 material, Mark I Control Valve with characterized upstream seat guide, 0.625” Ball Bore, Chrome Carbide Hardcoated A182-F6a Ball and Integral A182-F22 Seat, Zero Leakage

Thanks!

Matt

 

[stanier]

Go with the Valve Technologies selection. You could also consider CCI or Drag.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[Latexman]

You didn't give prices! I know a contractor doesn't give a hoot, but the client will.

What's the Cv of each valve at 20% and 80% open? If you want help, give us some data that is helpful.

What noise level is expected of each valve? I agree with stanier, you should fax a spec off to CCI, quick! It'll be extremely expensive (more mark-up for the contractor!), but it'll be quiet and last forever!

I expect more than this from a fellow NCSU graduate! Anticipate!

Good luck,
Latexman

 

[MattNCSU03]

Thanks for the reply, I have contacted CCI and they are working on a quote. I don't have a price yet on the Fisher option but I'd expect to to be less than the ValveTechnologies valve which came in under $2,500. Not even a drop in the bucket for a base-load 1220 MW power plant. No mark up from us, we are just doing the design, the plant is handling procurement/installation. I'm working on getting some more data from the valve manufacturers. Will let you guys know...

 

[Latexman]

Comparing your min., normal, and max. req'd Cv's to the available 20% and 80% open Cv's gives you an idea of operability and turndown.

Good luck,
Latexman

 

[MattNCSU03]

From the curve supplied by Fisher, the CV for the Fisher valve with a 3/8" diameter port at 20% is about 0.25, and at 80% it is about 1.7. At the "normal" flow condition we're looking at 52% open/0.7 CV.

ValvTech is still working on a CV curve and CCI priced themselves out of consideration

 

[dcasto]

Just put in a 1" $200 needle valve.

 

[JLSeagull]

The condensate will be flashing as you drop the pressure. The small valve looks like an ordinary Fisher valve with HARDFACED trim. This sort of application could wire-draw the plug and seat when working near the seat. Consider a gap control or other means such that the valve is either fully closed or at least 30% travel when partially open. You don't want the big valve near the seat either.

 

[MattNCSU03]

ValvTech came back with their curve for a Mark I CV today...

% CV
30 0
50 .23
70 1.0
90 1.5
100 1.56

I asked them to defend their choice of the Mark I over the Mark III which has pressure reducing plates upstream and they said the Mark I is more than capable of handling the pressure drop. Both valves would operate between 50-70% open

 

[Latexman]

Flashing going on. Two-phase flow and choking and entrainment and EROSION. What's the hardness of the materials (the moving part and the stationary part) on the valve they offer? ALSO, whats the hardest material they offer that will fit in the valve once this one erodes so bad you have no control on the low flow side or too much leakage?

And once again, what are the prices? Comparable? % difference?

What is the warrantee period against wire-draw for these two valves? Just for kicks, what was the warrantee on the CCI valve?

Good luck,
Latexman

 

[MattNCSU03]

The ValvTech valve is about 25% of the cost of the Fisher

"Most of the pressure drop occurs in the Mark I upstream of the critical seating surface through the characterized orifice in the upstream seat guide. Your maximum pressure drop under normal conditions is only 278 PSIG. The seating surfaces of the Valvtechnologies Ball Valve are Chrome Carbide that has a Rockwell C hardness of 66-69.
Typical Valves use Stellite that is approximately 46."

The area downstream of the ball is "RAM 31 hardened" F22 and the upstream is "H.F." (hard faced?) F22.

I don't have any warantee info for any of the valves just promisses from the sales guys that they will last