split flow

[staffman]

I am planning of spltiing the flow of oil,water,gas into two heater treaters and am looking for the best way to accurately control and quantify the split flow. Any suggestions?

 

[JLSeagull]

Many methods exist. Consider a flow meter in each line after the split. Total the two flows. Use an adjustable restriction with one such as a globe valve, and a control valve with the other. Use ratio control for the control valve, using a ratio against the total flow. This permits 50% or other value for the controlled flow. The line with the manual valve would be described as the wild flow in some control descriptions.

 

[sshep]

Are you trying to split the flow of a mixed phase (VLL) stream? -sshep

 

[staffman]

Thank you JLSeagull, That starts me on the right path. I think that the set-up you are suggesting is a manual valve on one treater inlet and a control valve, I/P, controller and flow transmitter on the other treater inlet. Correct?

sshep, the mixed phase will consist of a 70% water and 30% oil emulsion and very little gas.

 

[JLSeagull]

I am suggesting a manual valve on one treater inlet; and a control valve, I/P, and ratio controller on the other treater. Consider symetrical flow transmitters on each treater inlet. You need to sum the flows in the control system and ratio against the sum for the automated loop.

If the distance is far (or other reasons make the manual valve adjustments from the control room), also consider an I/P with HIC in the DCS for the manual valve.

 

[sshep]

Control scheme selection depends on how the total flow is being controlled, piping layout up stream and downstream, and what disturbances are expected. You might consider a three way control valve, especially if you must handle a wide variation in total flow, or you expect downstream pressure variations in each branch.

The three way valve simply acts as a diverter to split the flow. I like three ways valves for this purpose. The only downside can be cost for large pipe sizes- a three way valve requires more metal than an equivalent line valve.

best wishes,
sshep

 

[staffman]

Thank you very much JLSeagull and sshep. THe information you have provide has given me a path to start on. Thank you again.

 

[roker]

hello,
two phase flow is dificult to control, so try symmetrical lines.

regards,
roker

 

[MikeHalloran]

It's possible that hydraulic flow splitters (identical gear pumps with the shafts linked) would work for you in this particular application.



Mike Halloran
Pembroke Pines, FL, USA

 

[SeanB]

Personally I would not use a manual valve on one inlet. If you are trying to control flow - use two control valves. If not you will have an operator contstantly tweaking this valve trying to balance flow. Remember, the flow is going to take the path af least resistance. If your total flow drops off, your controller is going to pinch down to compensate, but your manual valve will have the same opening and hence you will get less flow through the controller, but increased flow through the manual valve.

 

[staffman]

Thank you all for the great advise. You all have provided me a path to begin. thanks again!!

 

[JimCasey]

I'd lean toward using a 3-way diverting ball valve. They are pretty simple. With porting for 90-degree operation, all the flow goea to one port at zero degrees, and all the flow goes to the other port at 90 degrees, but in between, the flow is split between the two outlets.

 

[MikeHalloran]

OR, if the downstream device's inlet doesn't need to be pressurized, pump the soup into the bottom of one cell of a three- part box. Drain the other two cells into the magic treaters, or whatever they are. The open top box releases the gas, and two weirs between the cells balance the flows and allow visual confirmation.



Mike Halloran
Pembroke Pines, FL, USA