Control Valve Sizing


Thread Starter


I have the following process conditions:
Flow Rate ----------- delta P across calve ------------ Process Media
min 30.000 bbls/day ----- 135 psi ------------------------- Crude Oil
max 60.000 bbls/day ----- 185 psi ------------------------- Crude Oil

Pipeline = 12" . Valve Body = 8"

Although i selected large valve with CV=500 I am still facing cavitation!

Any suggestions?

It's possible that you will find a solution to a problem like this one through this forum, however I would much more advise you to contact the valve vendor.

They have greater expertise to apply to your particular problem and are more intimately aware of potential problems that could crop up later on.

Wanting to solve a problem yourself is commendable, but you need to have sufficient knowledge and experience to perform it. Although you do want to solve the problem yourself, it appears that you lack the knowledge and experience to do so. It will not be seen as a weakness on your part to approach the vendor for their solution. As a result, you will get a solution sooner AND you will gain some valuable knowledge and experience in the process.
I suspect the poster is just trying to solve a theoretical problem. we are looking at a valve that would be in the range of $50,000.
135 psi is a lot of pressure drop and a huge waste of energy at those flow rates.


The high pressure is used for pressure packing of a 45 km trunk line to avoid flashing and two phase steam. the downstream pressure after the valve is the static head of a storage tank of 12 feet high + neglected friction loses which gives about 17 psia at the normal operating level of the tank.

The vapour pressure is assumed to be 13.9 psia
Due to pressure downstream the valve is 17 psia which is very close to vapour pressure. I suppose if i am not mistaken that the pressure in the vena cotacta is below vapour pressure and bubbles formation and cavitation occurs. correct me if i am wrong.

We have suggested the EPC contractor to use an orifice plate after the valve and avoid getting the pressure downstream the valve near the vapour pressure.

>I have the following process conditions:
>Flow Rate ----------- delta P across calve ------------
>Process Media
>min 30.000 bbls/day ----- 135 psi -------------------------
>Crude Oil
>max 60.000 bbls/day ----- 185 psi -------------------------
>Crude Oil
>Pipeline = 12" . Valve Body = 8"
>Although i selected large valve with CV=500 I am still
>facing cavitation!
>Any suggestions?


You may use a triple offset/ eccentric valve for such application. However, in the present scenario, it is better to avoid sudden expansion of the line. 8' x 12" expander/reducer or venturi may be added after 6 mtrs from valve discharge.


would it make any difference to use butterfly valves?

I presume butterfly valves are used at high CV values where high flow is considered with small delta p across the valve.

> Did you consider to use butterfly valve?