what to consider in sizing / picking the right pump?
what to consider in sizing / picking the right pump?
(OP)
we are interested in replacing an existing pump with a bigger pump. mainly the reason is we want increase the transfer rate by replacing the pump.
can someone help on the things we should be considering in sizing the right pump.
thanks
can someone help on the things we should be considering in sizing the right pump.
thanks





RE: what to consider in sizing / picking the right pump?
What kind of pump do you have? Have you examined the hydraulics of the system to determine if there are any oppurtunities to debottleneck the suction or discharge piping? Develop a system curve for the existing system and this will be more clear. With this info you can perform a cost benefit analysis for determining whether piping upgrades will be beneficial if there are oppurtunities to debottleneck the system.
If your hydraulics determine that you must upgrade the size of the pump and the pump vendor can not help by upgrading the existing pump, you must obviusly provide the pump vendors with a system curve and work with them to select a pump for your system.
If you are unfamiliar with hydraulic calcs and their signifigance in determining selection of a pump, then you need to study up or ask the assistance of a more experienced engineer.
RE: what to consider in sizing / picking the right pump?
its a centrifugal(3 x 1.5 ", 3" suction nozzle, 1.5" discharge nozzle) pump for a 9 mile transfer line. the suction and discharge side pipe size is 6". the distance from pump center line to bottom of tank is very minimum, less than 5ft on the suction side. height of the liquid is about 30ft.
on the discharge end, the distance from pump centerline to inlet of tank is about 30ft.
I also wonder what is the maximum flow we can have for a given pump
RE: what to consider in sizing / picking the right pump?
RE: what to consider in sizing / picking the right pump?
RE: what to consider in sizing / picking the right pump?
link to pump curve
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RE: what to consider in sizing / picking the right pump?
RE: what to consider in sizing / picking the right pump?
Balance the need for a good NPSH margin with the need for a lower suction specific speed. In this analysis, be realistic. The NPSH(r) is sometimes based on a group of worse case assumptions: lowest possible tank level, highest possible product viscosity, highest possible vapor pressure. If the convergence of these unlikely extremes is impossible, then don't design for it. If you are overly conservative about the suction head, it may drive you to buy a pump with a higher Nss which will limit the downturn.
Allow for unusual operating modes. In tank services, we size pumps to transfer the product faster. That is what the pumpers want. But, if they have to drain the tank to change to new RVP requirements seasonally, it can be a problem. When you want to set the floating roof on its legs, or re-float it, you have to go very slowly. A large pump might be incapable of running low enough in flow to meet the regulations for re-floating the roof. You might need a spill-back line to allow for these unusual conditions without destroying the pump. Or it might be worth the price to add a smaller heel pump to handle the low flow condition. I personally, believe that the minimum flow value given by the pump company can often be too low. Determine a more conservative minimum flow based on Nss and specific speed.
Ask what the future might hold. We recently bought a pump that was for a fuel oil desulfurizer. Three weeks after it was started up, they got an idea that they could capture a high profit by switching the unit to hot gas oil. The design of the pump (materials, gaskets, etc.) needs to be able to handle the new service.
Johnny Pellin
RE: what to consider in sizing / picking the right pump?
RE: what to consider in sizing / picking the right pump?
If you don't have a pressure relief valve on downstream side, and if you do have any valves or any way to close off piping downstream of the pump, then your downstream piping must be designed for pump shutoff pressure of the new pump. And if you do have a PSV, then it may need to be changed out to meet new relief case flow rate.
RE: what to consider in sizing / picking the right pump?
The capacity of your pump is dependent on the size (Kw/HP) of your motor. If you increase the pump speed by using a pulley and belt arrangement you will also improve your flow, but you may require to change to a higher Kw motor. With a pipe line this length you can expect large losses due to pipe friction.
Offshore Engineering&Design