Westfalia D10 Purifier, Speed Reduces

From what little information you have given, it's hard to say....but my first inclination is that the rings are out of balance...What is your vibration level?

New yard delivery ship.new purifier... New parts.

What are the specs on the rate? ..and what is the range you are experiencing? How long have you let it run? Is this for oil, water??

Put the top down.

If its what I think it is, a motor driven pump, pulling a (partial) vacuum is effectively a lower "load" on the pump, than when the valve is open, and whatever is being pumped (liquid or gas), "loads" the motor up and slows it down.

This can happen with almost any liquid and gas being pumped.

This is a well understood "happening" or "Phenomena!"

An easy example that most can try at home is when a vacuum cleaner intake is "blocked" , the motor speeds up, unblock it and it slows down!!

But as the details are so sparse, I may have misunderstood the problems experienced......

Assume from cryptic description that this a shipboard centrifuge for removing water from an oil system. Is your discharge partially blocked and you're adding fluid faster than you're discharging and creating too much of a drag on the cones?

Other thing to consider is belt slippage. If in re-building/repairing someone got oil on belt or didn't insure proper tension, the loading can create slippage and slowing down.

Maybe you've overloaded it, Mildred.