I have 5, 12 v dc vaccum pumps. The vaccum pressure they can maximum achieve is -450 mm oh hg. can i connect them in series to get a vaccum of -750 mm of hg. I calculated this according to the compression ratio.
Aditya,
It's unlikely to work this way - every pump operates optimally within a certain range of inlet pressures. Some designs are more sensitive to pressure than others (turbo pumps: I'm looking at you...) and simple diaphragm pumps (which I suspect might be yours) are less sensitive to inlet pressure.
(they'll shift the contents of their closed volume pretty much indepedently of its pressure)
Give it a go - I hope to be surprised!
Thank you James. I have connected them in series and have achieved a maximum vacuum of -747 mm of Hg. Yes my pumps are diaphragm pumps.
These pumps likely have a (one way) check valve at the outlet which is actuated upon compression of the diaphragm. On the evacuation portion of the cycle the valve closes. As such there is a minimum pressure differential required for pumping action to occur. Adding a second pumping stage should result in lower base pressure at the inlet, however one reaches a point of diminishing returns adding additional series stages. Ultimately the inlet pressure will be limited by reverse leakage of the check valve and diaphragm seals.
Aditya Vemulapally Can you supply the formula your calculations please?
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