Pressure reduction 1

[tomol]

Hi,

I am currently work on two different cases where I need to reduce pressure in a seawater pipe.

1. 10", flow rate 690m3/h, pressure drop 4,5 barg
2. 10", flow rate 1600m3/h, pressure drop 9 barg

Today we have installed orifices but these are creating cavitation and the vibration and noice is of the scale.
We are considering to install control valves but as we are then talking about titanium the cost will be a major issue.

So my question is, is there anybody that have experienced similar problems. I am looking for an alternative to the orifice. Something less costly than the control valve.

Any ideas would highly appreciated.

Tom

 

[CostasV]

If I understand corectly, you need the pressure drop only when there is flow, otherwise (if there was no flow) the orifice would have no effect in pressure drop.

As an alternative for orifice, you could consider a (significant)length of pipe with a diameter of about 2".


Costas

 

[tomol]

Hi Varsamidis,

Thanks for your input, do you have knowledge of a company that can do a calculation/ simulation for something like this? We need to demonstrate that the cavitation and noice level will be at an acceptable level.

Tom

 

[sathanasiou]

The flow is way too big for the 10" pipe! You should increase the pipe diameter or connect a second 10" pipe in parallel with the existing one to distribute the flow. You will need a collector where the two pipes meet.

For the second case (1600 m3/h) you will need more than two parallel pipes to handle the flow.

Probably this solution is more expensive than the control valve...

 

[CostasV]

tomol, sorry I can not help on the demostration for the noise and cavitation.

My idea was to have lower maximum velocity (than the one with orifice)and also to gradually increase (and decrease) the velocity.

I should ask first what is the orifice diameter and then propose the diameter of the (significant) length of pipe.

Costas

 

[tomol]

Hi Costas,

I have found a company which are helping me with the noice calculations. We are currently looking at the 10", flow rate 690m3/h, pressure drop 4,5 barg problem as this is the simples of them. A it looks now this can not be done with one orifice. We are now looking into other possibilities,, such as a "multi-step orifice",, maybe in combination with a butterfly valve.
If you ever have a similar problem,, Per Salvesen at Autek (Norway) is your man. He does the calculations and supplies the orifices you need.
I have had some problems finding somebody that can do calculations. The calculations from the first one I found was totally of. Therefor I didn't inform Autek that I had meassured 108 db at the first orifice. Their calculations hit straigth on target (not that it helps but at least it shows that they know what they are talking about).

Tom

 

[abcmex]

Tomol,
you may use several single orifices in series. one more option is a low-dB orifice plate see thread378-41153.

regards