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Anonymous Poster

Clearance Measurement Question

12/13/2009 5:06 PM

why are the clearance measurements between the impeller and the pump casing at the wear ring for a cetrifugal pump with a fully shrouded impeller important.

and also the same question for one with a semi open impeller.
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Steve S.
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#1

Re: Clearance Measurement Question

12/13/2009 8:43 PM

It is a direct indication of pump efficiency. The higher the wear ring clearance the more recirculation, and the lower the efficiency.

The wear ring is there to keep liquid form leaking by. If the wear ring is worn out (high clearance) the pump efficiency reduces the bearing loads increase, and there is high potential for pump damage.
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Tornado
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#2

Re: Clearance Measurement Question

12/13/2009 8:56 PM

Whether the impeller is fully enclosed or not, high pressure liquid from the periphery of the impeller can pass inward along the outer surface of the impeller and reenter the suction stream. The wear ring arrangement, with its small clearance, minimizes this recirculation. But wear rings do indeed wear over time, enlarging the clearance, bypassing more liquid, and decreasing the pump efficiency. Many if not most pumps make the wear ring a renewable part so that the small clearance can be restored simply by screwing or pressing in a new wear ring.

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#3

Re: Clearance Measurement Question

12/14/2009 3:34 AM

Increasing the clearance reduces the pump's performance.

Reducing the clearance reduces the pump's effectiveness at passing the occasional solid, which may have an impact on its lifespan.

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otha
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#4

Re: Clearance Measurement Question

12/15/2009 8:00 AM

The term wearing rings is somewhat misleading. the purpose of the rings is to "seal" the discharge side from the suction side of the pump.

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otha (1); PWSlack (1); Steve S. (1); Tornado (1)

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