13 replies to this topic

[panagiotis]

Hello everyone,

There is a system where a fluid is pumped from a tank to a filter. The fluid is fed at the bottom of the filter and it exits at the top.
At the inlet line of the filter there is a PSV.
My question is what could be the overpressure scenario?
Between the pump discharge and the inlet to the filter there are a few fittings and an automated on/off valve.

[breizh]

Hi,

Filter plugged. Very common for cartridge/basket filter.

Breizh

[panagiotis]

But the PSV is before (at the inlet) the filter?

[panagiotis]

Hi Breizh,I understood what you mean!!

[fallah]

There is a system where a fluid is pumped from a tank to a filter. The fluid is fed at the bottom of the filter and it exits at the top.
At the inlet line of the filter there is a PSV.
My question is what could be the overpressure scenario?
Between the pump discharge and the inlet to the filter there are a few fittings and an automated on/off valve.

 

Hi,

 

The overpressure scenario would be created due to pump shut off (following to on/off valve close stuck/inadvertent closing, or filter plug) and the magnitude of the overpressure is pump's shut off pressure (supposing the pump type is centrifugal), hence the on/off valve shall be installed after PSV inlet line branched off from the pump's discharge line.

[panagiotis]

Hi,

Thanks for your reply.
If we assume clogging of the filter, then the relief capacity can be read from the pump curve and it will be at flowrate close to the shut off pressure, right?

One more question what is the reason of having the on-off valve after the PSV?

[fallah]

If we assume clogging of the filter, then the relief capacity can be read from the pump curve and it will be at flowrate close to the shut off pressure, right?

One more question what is the reason of having the on-off valve after the PSV?

 

Hi,

 

The relief load of the PSV should be equal to or higher than the pump's minimum flow per the value specified by relevant pump's vendor.

 

Reason of having the on-off valve after PSV is to avoid PSV inlet line blockage due to pump's discharge line blockage following to inadvertent (loop malfunction, ...) closing of the on-off valve...

[breizh]

Hi,

To me the reason of the valve is about maintenance/operation to replace the cartridges or to clean the basket minimizing the spillage.

Breizh 

[panagiotis]

Hello both,

 

Fallah, it is clear that the minimum flowrate will be the relief capacity. And it makes absolutely sense! To add something, the set pressure of the PSV could be same with the design pressure of the filter (which is not necessary to be the same with the shut off pressure of the pump).

 

Regarding the position of the on-off valve, I understand that it is better to add the on-off valve after the PSV in order to protect the whole discharge line? Am I right? 

 

Breizh, what you say it is correct about the purpose of the on-off valve. Its location is a different story!

[breizh]

Let you provide a sketch!

Most probably the weakest point in your system is the housing of the filter.

Breizh

[panagiotis]

The approach would be completely different if the pump was positive displacement?

[panagiotis]

Hello again,

What approach should I follow if the pump is positive displacement?

[fallah]

Hello again,

What approach should I follow if the pump is positive displacement?

 

Hi,

 

In general, you should consider a PRV at the pump discharge as close as possible to the pump.

[shvet1]

Hello again,

What approach should I follow if the pump is positive displacement?

 

Overpressure protection is mandatory

No shut-off valves between pump and pressure relieving device

Pressure relieve stright to suction in most cases

Compare pump pressure profile with PRD's set and reclosing pressures - if pulsation dampener is required