OK a bit different - min capacity is something that you state to the vendor as often pumps have a range of flows that they need to operate within. Normally this is not less than 50 to 60% of the "rated" flow. Minimum head is different - not sure why you would state this to a pump vendor, only required head.
Is this for a centrifugal pump or a PD pump??
~Usually you state rated head and flow and maybe min normal flow, but not head as that is your problem, not the pump vendors. All he can do is give you a pump to match your required duty, including min continuos flow, and then you work out everything else from the pump curve he gives you.
I still think we're at crossed purposes here though....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Can you describe your system and needs more clearly. So far, this looks a bit like a "homework help" question.
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.
Minimum flow for a centrifugal pump is generally about 20% of BEP flowrate in many cases, not all.
You can look for the head at that flowrate on the curvre to get an idea of what it will be.
I am designing a sewage lift station. The requirements are 1440 gpm at 87 TDH. The pump I picked out is a Myers 6VC with 113/4" impeller attached is the pump curve. The specs I was given to use has a minimum secondary capcity and head. I contacted the manufacturer and they told me it was 800gpm and 110 TDH but for the life of me I don't understand how they came up with this info and of course the salesman couldn't explain. Also I did an internet search and couldn't find any information.
If anyone can explain what the secondary head is I would appreciate it.
I assume you have chosen the 1750 rpm version as it's the only one which matches your capacity and head.
Still can't figure out the secondary capacity figure though. All I can think is that it is either a recomended min flow to still be reasonably efficient, or perhaps the second point that they actually test the pump at??
Actually, giving it even more thought, I think perhaps it is an opportunity for a designer to put two duty points to the vendor, i.e a main duty point (your 1440 x 87 ft hd) and also a second duty point for lower flow but higher head to see if the pump can do both. This might occur for example if you're filling a large tank and at the start you will have one flow rate and one head, but when the tank is nearly full (assuming it's quite a tall tank) you still want to have a certain min flow rate, but then need a higher min head. This is just an educated guess by the way.
If you only have one fixed duty then you don't need it.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Lift stations usually have a low level and a high level and the pump needs to operate at both.
There are process constraints that may require the owner to specify minimum flows/heads for the system. The end-user (through a consultant) should use the min flow & head spaces on data sheets to specify these if they are relevant.
A pump manufacturer's model selection may well be impacted by such information.
Meyers makes a good product, but not always Represented well.
I am surprised the salesman didn't know how to explain something to you. Aren't they normally engineers too? Zoeller has some useful things to read in case that helps.
