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# Max injection rate through the choke

## Max injection rate through the choke

(OP)
Hello colleagues!

I have some challenge calculating water injection wells.

Some wells with low Pres are absorbing and the injection rate is thus constrained by the chokes (of course cavitation and erosion is inevitable in this way but we could not decrease injection pressure).

How could I calculate Max rate of WATER through the choke (for example for the 4 mm choke and Pup=200 atm) and under what pressure ratio it will occur?

All methods I have found are for the gas and two-phase choked flow, but for the liquid?

### RE: Max injection rate through the choke

You find the Cv of the valve at whatever your opening position is from the choke manufacturer and use that in the relevant equation for gas or liquid (ask Mr google)

Or ask the choke valve supplier if you give him the inlet and outlet pressures.

If you're getting cavitation and erosion, your answer will not be valid for very long and you then really need a different trim / valve so that it doesn't cavitate or erode

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

### RE: Max injection rate through the choke

(OP)
Thanks LittleInch, but I'm working in Kazakhstan and I'm not sure I could find Cv curve for simple choke bean (3 cm lenth).

Futher, Cv is applicable only for pressure ratio lower than critical: above the critical PR the flow is constant and I wish calculate this value in Pipesim when I simulate my injection system.

### RE: Max injection rate through the choke

Have a look at this and see where you stand. http://www.documentation.emersonprocess.com/groups...

The value of the internet is that it doesn't matter where you are - information like this is available if you look for it.

However you still need to find the data for the valve and internal trim that you have.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

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