RE: Failure of pumps in Hydropneumatic System

From: <Steve>
Date: Mon Jul 14 2003 - 08:40:00 EDT

Hi Rajendra Bajikar

nothing wrong with a bronze impeller if the water quality is suitable. Bronze seems to work OK on ships propellers. You need to investigate the cause of failure thoroughly. 7.5 HP is getting large for a monobloc - you are asking a lot from the motor bearings.
If frequent starts were the problem I would expect motor winding, bearing and seal problems, not impellers falling to pieces. It is difficult to guess at the cause, but I would look at the overhung load and impeller balance. Some monoblocs appear to have excessive impeller overhang. With a poorly balanced impeller, vibration could cause fatigue problems around the blade tips. These are design issues, not application issues.
Your contractor appears to think 1 year is an acceptable service life. If he selected the pump brand then you have part of your answer.

Cheers

Steve McKenzie

-----Original Message-----
From: rajendra bajikar [mailto:rajendrabajikar@yahoo.com] Sent: Monday, July 14, 2003 11:44 PM
To: <a href="/group/PipingDesign/post?postID=7Tcko-AFjRgJ98K--hrgZK6_-hrdcrMh2piVaAKBZxg0FX0OT82IJlyfyPuXy_24CAGml5ZkN2_V-wUNOcrarwgI">PipingDesign@yahoogroups.com</a> Subject: [PipingDesign] Failure of pumps in Hydropneumatic System

Dear Group Members,

Two Monobloc pumpsets each 7.5 HP, installed on a Hydropneumatic system for domestic water supply failed due to fracture of Bronze Impellers after about one year of service. No evidence of foreign matter was found in the pump casing.
Are Monobloc pumpsets not suited for Hydropneumatic service due to frequent start-ups?
Could you please tell me where could I find general guidelines on this service?
The contracor's performance guarantee is over and he is suggesing replacement with same pumps.

Thanks and regards,
Rajendra Bajikar.

Rajendra Bajikar.

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Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Mon Jul 14 08:40:00 2003