1 st pump operating delay to shut off after 2 nd pump comes into operation
1 st pump operating delay to shut off after 2 nd pump comes into operation
(OP)
I have a question, anybody could help? We have two pumps 1 main / 1 spare, if we would to switch the 1 st pump to 2 nd pump in operating, and do not want to shut off the 1 st pump for few seconds, then how would be a reasonable delay we can consider to operate the two pumps before the 1 st pump shut of come for not having problem for the pumps and the system? (How many seconds?) If it delays long what would happen? The pump is centrifugal, what if it is PD pump?





RE: 1 st pump operating delay to shut off after 2 nd pump comes into operation
Independent events are seldomly independent.
RE: 1 st pump operating delay to shut off after 2 nd pump comes into operation
PD pumps on the other hand will more or less instantly double the volumetric flow rate and it is unlikely that your downstream system will be able to cope with that without a large increase in pressure, possibly either causing the systme to shut down or lift the bypass or pressure relief systems if run for more than few seconds together. Rapid (5 seconds) turn off of the main pump is recomended unless yur system can cope with two pumps running. Only you can tell.
Transient analysis is the only way to really see what would happen.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: 1 st pump operating delay to shut off after 2 nd pump comes into operation
Can you explain your system and concerns in much more detail. As originally stated, your posting looks suspiciously like it may be a request for help with homework.
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.