Need Info about V-notched Gate Valves

[Chance17]

I am currently working with a Client that needs two 2" V-notched gate valves.
The devices will be used in in Slurry service to maintain min flow at a centrifugal pump.
The required flow is betewwn 60-120 gpm. The process fluid is oil at 580-F and 220-psig.
I have two problems
1) What sizing equations should be used?
2) Where can the gate valve be procured?
One may direct me to ask the client -- but he does not know the answer(s)
I have also extensively searched Google and could not discern any answers.
The Web has plenty of Vendors selling Knife Blade V-notch - but these are inappropriate for the service.
I have also searched this Web site.

Any and all comments will be appreciated.

 

[gerhardl]

I would not personally recommend a V-notch gatevalve for this service. I believe a V-port ballvalve would be easier to find comercially, better suited, better for regulating, and probably much cheaper.

If 2" is the main pipeline, I would, before throtteling with a V-port, have looked into two other solutions: a) Pump speed regulation or b) shutting down mainline (on/off automated) and smaller bypass, if necessary with smaller, regulating valve with for instance regulating cone in the bypass line.

I have been involved with knifegate valves for throtteling pumped wastewater by normal temperatures. This was mostly used for larger diameters, say 200mm up to 600mm. The 'notch' was arranged as a complete 'blindplate' mounted directly in the valve housing, directly beside the normal sliding gateplate. The 'blindplate' machined with a regulating triangular hole, tip down, to regulate on the low-flow side, or a pentagon formed opening, tip up, to regulate on the high-flow side. Dropthight closing because of the construction, also at zero pressure.

For parallell pumping into common mainline this gives some sense, but for small lines and flow?

The manufacturor would be the right supplier of flow and dimensioning data.

(A tip for V-port ball-valves could be the type suitable for steam. Be sure to get one suitable for the temperature and fluid (oil) resistant sealings.)

 

[TD2K]

Why not just install a small bypass around the gate valve to maintain minimum flow? If necessary, install an orifice to set the flow at a desired rate.

 

[reverman]

Could the "V Notch" just refer to a normal gate valve with the bonnet cavity vented?

One method of venting the bonnet cavity commonly used on small cryogenic gate valves is to "v notch" one side of the wedge. Basically you take the wedge and cut a chunk out of one side to allow the bonnet cavity to vent any potential over pressurization typically upstream.

This can be done on any gate valve and is a pretty cheap modification.