5 replies to this topic

[farid.k]

hye all, what if i install valve instead of install orifice in order to control the downstream pressure? objective is, i dont have to do orifice sizing, plus i can manually regulate the valve untill i get desired pressure. Any comment? this is for small pipe size (1")

[oscarsender]

In orifice you have a desired downstream pressure and a corresponding fixed flow rate will pass through it. If you use a valve, you may obtain your desired outlet pressure but the corresponding flow rate will not be the same as that of orifice at same pressure drop.

Edited by oscarsender, 20 July 2014 - 12:14 AM.

[fallah]

farid.k,

 

For a fixed upstream pressure, by sizing a RO one can adjust to have a fixed downstream pressure with a specified flow rate. But if you have a variation in upstream pressure and doesn't matter having flow rate variation, it's better considering a manual valve instead to adjust the downstream pressure...

Edited by fallah, 20 July 2014 - 02:13 AM.

[farid.k]

farid.k,
 
For a fixed upstream pressure, by sizing a RO one can adjust to have a fixed downstream pressure with a specified flow rate. But if you have a variation in upstream pressure and doesn't matter having flow rate variation, it's better considering a manual valve instead to adjust the downstream pressure...

whats wrong if have fixed upstream pressure, we use manual valve? Using Orifice, we calculate, we get the desired pressure. But using valve, we open it slowly and when get the desired pressure, just remain that opening. both option fulfill the objective am i right?

[PingPong]

You cannot use an orifice plate to control a downstream pressure.

If your orific happens to result in the desired downstream pressure then that is pure luck.

 

An orifice plate is just a stupid plate with a stupid hole in it. It does not control anything. It is just a fixed restriction in a pipe.

 

Orifice plates are only suitable to roughly create a purge flow between two more or less constant pressures, and whereby it does not really matter whether the actual purge flow rate is 20 % higher or lower than intended.

[fallah]

farid.k,

 

As i mentioned if the flow rate difference doesn't matter, both options fulfill the objection i.e. adjusting the downstream pressure on a prespecified value...