## Multistage restriction orifice calculation

## Multistage restriction orifice calculation

(OP)

thread124-150149: Restriction Orifice

Hi all,

I've been reading that thread about Restriction Orifices and I still have some doubts.

In our case, we must design a multistage device, wich includes 3 restriction orifices in series. Is there any difference between multistage and simple restriction orifice calculation? I've seen some links about this theme but unfortunately I don't have access to that ones.

I've been calculating that device orifice by orifice, using intermediate pressures and pressure loss, but results aren't still those I hoped to be.

Hi all,

I've been reading that thread about Restriction Orifices and I still have some doubts.

In our case, we must design a multistage device, wich includes 3 restriction orifices in series. Is there any difference between multistage and simple restriction orifice calculation? I've seen some links about this theme but unfortunately I don't have access to that ones.

I've been calculating that device orifice by orifice, using intermediate pressures and pressure loss, but results aren't still those I hoped to be.

## RE: Multistage restriction orifice calculation

## RE: Multistage restriction orifice calculation

Does anybody know how to calculate a multistage restriction orifice device?

## RE: Multistage restriction orifice calculation

## RE: Multistage restriction orifice calculation

the multistage device is used because we need to decrease pressure from 40 to 5 bar. this kind of devices are used to gradually decrease pressure

## RE: Multistage restriction orifice calculation

## RE: Multistage restriction orifice calculation

## RE: Multistage restriction orifice calculation

The article is still available to anyone who needs it and I still get the occasional request for it.

Essentially, you start at the back and determine the maximum dP you can take across an orifice to avoid cavitation and then use that pressure as the outlet pressure for the next orifice and so on up the line.

## RE: Multistage restriction orifice calculation

The purpose for multiple orifices is to reduce noise , and to provide a backup orifice when the final orifice erodes down. The use of multiple orifices of exactly the same diameter will not change the flow vs upstream pressure correlation unless you have sufficient number to cause "frictional choking", .

The calculation of choked flow thru a series of orifices is a classical problem in compressible flow theory, and under the assumption of a "perfect gas" , the choked mass flowrate ( of W/A vs Pi/Po ) is only a function of the orifice that has the smallest area.

If the fluid is erosive, then it is best to either use a SS "capillary tube" or one of the engineered velocity controlled multiple stage devices, such as the CCI flow restricotr .

## RE: Multistage restriction orifice calculation

Itteration should only be required for a flow calculation- i.e. to find the flow through a system of known orifice sizes and boundary pressure conditions. This can be done by choosing flows (start low and work up) until the outlet pressure from the last orifice equals the boundary condition.

That's my opinion anyway.

best wishes,

sshep

## RE: Multistage restriction orifice calculation