Pump calculation in high rise continued

[SAM12074]

I saw a closed thread of the same name above and found it very helpful to help me to confirm what I was thinking with pipe and pump design in high rise applications. One question I had is in calculating the max working pressure at the top of the building for selecting expansion tanks. Using the example of the 900 ft high rise with 140 ft of piping losses, what is standard practice for calculating the max working pressure at the top of the building if the pumps are in the lowest level. The safest route appears to be that you just use the pump shutoff head--assume 160 ft. Could you subtract the 900ft of pipe friction losses from the pump shutoff head to establish the max pressure at the top?

 

[LittleInch]

No. Think about it - pump shut off means there is no flow so no pressure drop due to flow.

your expansion tank is there to limit pressure but also maintain a positive head at the top of a building if we're talking about a closed loop circulation.

But we don't really know what you're thinking about or what that previous thread said...

But this is why you usually try and locate the pump and expansion tank in the same place and pipe it to the inlet of the pump.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EnergyProfessional]

Expansion tank has to be at the point of zero pressure change, which is the pump inlet or very close to that.

The pressure on top has to be above atmospheric when pump is off, or the de-aerators won't work. Consequently the bottom of the system will be under very high pressure. The pump and expansion tank and all other devices need to withstand that pressure. On the discharge side of the pump you also add the pump head at full speed and no flow (safety in case of blocked flow).
if the pump is on top, things are easier, maybe.

That is why tall buildings separate the loops. 900ft building, that is over 390psi. So if the pump is at bottom everything downstream of the pump at that level has to be rated way over 400psi. Not much equipment is rated for that. Look at this book.

 

[lilliput1]

You have to break off piping loops to not exceed pipe equipment pressure rating by using separate heat exchanger for each loop. Allow for approach temperature difference between fluids and always design for counterflow.

 

[chicopee]

My two attachments deal with a problem presented by Pefley and Newnan in their soft cover book "Mechanical Engineering license review" and note the assumptions which you may or may not implement. I don't have time to answer your OP however those attachments may provide valuable insight into your inquiry. I may have to submit two entries for my attachments.

 

[chicopee]

My second entry