Water Pump

Is there maybe air in the lines?

What size pump?

What is in the pump, its temperature and pressure?

How much suction head is there?

Is the pump trying to pump something it shouldn't, such as potatoes, a cable tie, a squirrel or a house-brick?

May be foundation bolts are lose,alignment not good,no vibration isolators under baseframe or discharge line.

What is the application - fully described - Nihal?

My gut-feel is a damaged and, therefore unbalanced impeller.

That might have been the house-brick....

Is it still on the manufacturer's published performance curve against which it was specified, procured, installed and commissioned?

What is the maintenance regime on this pump? What spares are to hand?

First of all, these folks are just chasing their tails without any real validity to their theroy's.

Do the following:

If you have a close coupled pump, check: Impeller & Mechanical seal

If you have a pump with a coupling, check the rubber material, If rigid & cracks replace it.

Every hydronic system will also include air vents at high points, so it's not air. Unless the air is being pulled from around a system component.

This is always a due process of illimination method, so get to it and report back.

You making it sound like its out fault that there was not more information provided in the OP. Me also thinks you are chasing YOUR tail big time.

The air vents you mention in the "hydronic" system would vent the air unless its pulling it in somewhere??? Which one is it? Can there be air in the system or not.

Is that your theory?

Welcome in the Guessing World of CR4.

My small irrigation pump (Yamaha 5 hp model), also gives a real 'shake' as it gains suction. I have been putting it down to a normal torque reaction - going from an un-primed state to a primed one where the impeller is working, in the first instance, against air [no torque reaction] - and - , in the second instance, working against water [torque reaction].

It is the same effect as if one were to quickly release the clutch of your car.

I'm going to try Sherlock Holmes method here by making some assumptions.

Assuming you have a centrifugal pump,

and it is working within the operating curve

and close to the best efficiency point

and the motor for the pump is the one which came from the supplier

and that motor is in good condition

and it is electric

and the pump has regular maintenance

and is in good condition

and you are not experiencing cavitation

and your pipe work is in good condition

and you are pumping a fluid suitable for that pump

and your pump is belt driven from the motor!

I would deduce that the vibration is from the motor belt. What else could it be. Problem solved, next question.

Well it works for Sherlock, maybe not in real life but it goes to show the variables which you must consider and why this question cannot be answered without more info. You could probably double or treble the number of assumptions I made here if you think about it.