Centrifugal Pump

its what we call dead-heading.

We have done this in the design of sanitary process equipment using centrifugal pumps such as Alpha Laval.

Basically what happens is the fluid will head up. and continue to do so.

With most centrifugal pumps the power drawn will decrease. But don't leave it running against closed valve for too long as the liquid will get hot and eventually the pump will be damaged.

Codey

Ahhh, curiously this is sometimes a 'trick' homework question.

Most students stop short of giving the more involved answer, by only mentioning simple 'shut-off-head'.

But that leaves out a lot!

The vital thing to note when answering this question is that 'shut-off-head' is elevated to a value above the 'open-on-heels' value.

This results in a dangerous cyclic condition known a 'tumbling'.

This is where we get the phrase 'tumbling head over heels'.

No homework answer would demonstrate ones level of understanding better that one mentioning the possibility of incurring the dangerous 'tumbling' phenomena.

"'tumbling head over heels'"

Are you serious? If yes, could you educate me. The term tumbling is new to me, not to mention the phrase above, when used in connection with pumps.

This is where we get the phrase 'tumbling head over heels'.

Really, or is this BS, so far you said nothing, can you elaborate.

I'm not surprised the students miss "tumbling" out of their answers. They'd be "head over heels" with laughter writing it down

Tony, Pheonix, Lyn;

Work with me a little. This question bears a striking resemblance to homework.

I was just making sure that anyone eschewing the arduous task of actually reading the required material and learning the concepts, and instead opting to simply post their homework question in this forum; might respond with an answer well fitted to their level of effort and understanding.

So, yes, while 'shut-off head' is the correct term for the head developed when the outlet is closed, 'open-on heels' is a farse, as is 'tumbling' in this context.

While this one is blown, I do find utility and humor in constructing this type of response to future obvious homework questions. Perhaps, that is misguided though.

I'd appreciate your input on the subject. Perhaps if there is concensus, we could agree on a sign that might keep the ruse from being totally blown out of the water, as was the case here.

Actually, I had engineers fresh out of college. and fresh as in within 5 years out of college. Question like this could be homework, but it was also not unlike questions from greenhorns.

That is sad. At a minimum, I would expect even an engineer who graduated at the very bottom of the class, when presented with a question like the one posted, to be able to mentally walk themselves through what is likely to occur and why, and predict what system parameters would be indicative of such a condition. Asking for validation of one's line of thinking at that point is completely reasonable, but failing to put forth the initial effort is, at best, lazy.

Stick around. You ain't seen nothin' yet.

One that comes to mind, he recieved a Bachelors of Science in M.E. from Michigan Tech.

In his defense he was a decent engineer, but not one where he would be put into a lead engineering position.

After 19 years out of college, I understand it still holds true for him.

brk.....

If a pump is large enough...... and if it is made from cast iron.... and the motor has enough horsepower.....and water is the fluid

It can explode when the discharge valve is closed when the pump is running.

Heat will build up very quickly (in seconds), not slowly (over minutes)

Most seals require flushing. If the condition is allowed to persist for too long, expect the seal's performance to degrade to the point where the pump becomes unserviceable.