Series pump intsallation

[dianad]

hi,

I have an installation where the pumps avaiable in the market for that purpouse do not reach the head that i need to overcome the circuit pressure loss. Therefore, i wonder if i could install another pump after this 1st one.
Do you think that i need to leave some space between them or even install other acessories?

Thanks!!

 

[JRLAKE]

People do it all the time but to say it will work requires more info.

Also, it's hard to believe there are no pumps available in the market to meet the requirements. How long did you look?

 

[dianad]

The problem is that the pumps avaiable in the market are to large to fit in the avaiable area...they are larger...

 

[Artisi]

Is this part of your non-performance question you posted earlier? If it is it would be better to find the cause of the non-performance before worry about 2 stage installations.

 

[whoowho]

In response to 'dianad'. . . there are several pump issues to consider. Is the original pump a vertical turbine pump? If so, can more stages be added to achieve the desired head rise? Does the pumped fluid have a high viscosity such that the viscous fluid correction to pump performance lowers the pump discharge head to below the necessary TDH? Is the pump impeller trimmed to below the maximum diameter which the pump case can accommodate? If so, can the impellers be replaced with full-size impellers? Is the pump operation limited by driver horsepower?

 

[dianad]

Dear Artsi,

No, this is not related to that post. This is why i've created a new one.
I know that this solution applied for the other case was a stupid solution, because the problem could stay the same or become even worst and cause problems...

Thanks anyway!

Dear whoowho,

The pump is not vertical. It's a simple circulator. My concern is about valves, strainers, etc and the distance between the 2 pumps...


Thanks!

 

[Artisi]

The second pump can be installed at any point that suits the installation, however, ensure that the second unit is capable of the increased casing pressure. no need for a second strainer or any other valves than what would normally be required for the installation.

 

[whoowho]

dianad . . . you mentioned earlier:
My concern is about valves, strainers, etc and the distance between the 2 pumps...
Hmmm . . . my concern would be:
Occurrence of a potential surge problem if the downstream pump trips and the upstream pump remains in operation. Typically what could happen is the upstream pump rides back on its curve to shut-off head. However, if the flow through the downstream pump is stopped abruptly, such as due to a check valve closure, then the kinetic energy of the fluid approaching the downstream (tripped) pump is converted into pressure, and the resulting pressure spike will travel upstream at the acoustic wavespeed. The surge pressure wave can bang into the upstream pump and cause a waterhammer event, in which the pressure spike observed at the upstream pump is far greater than the pump shut-off head. If the pressure spike reflects off the upstream pump (or another upstream check valve), there can be a trapped high pressure wave that oscillates between the two pumps. . . which sounds like "bang...bang...bang...". To remedy this situation, it is suggested to install a pressure relief valve or a pulsation dampener in the piping between the two pumps. Another possible item to consider is to provide an ESD switch to trip the upstream pump in the event of a failure of the downstream pump.

 

[BillBirch]

It sounds to me that your problem is that the avalable area is too small, not that the pumps are too big. Pump manufacturers do not intentionally make pumps too large - they would cost too much and would never sell any! One common solution to get a smaller pump, with higher head and flow is to go for a higher speed moter - 2 pole speed, if you have only been looking at 4 pole only.

You do not mention service, i.e what fluid, flow ratr, head. Perhaps a vertical pump with a flange mounted motor will decrease your footprint.