REDESIGN OF VERTICAL PUMP TREBLES MEAN TIME BETWEEN FAILURE

CHALLENGE

A post-installation modification to improve flow in a vertical chemical pump had weakened the discharge elbow. Subsequent cracking had been weld-repaired several times, but the pump was increasingly difficult to maintain. The customer asked ClydeUnion Pumps to undertake a redesign of the discharge elbow to prevent further deterioration.

SOLUTION

The modification that had caused the failure was undertaken originally because the gland ring outlets on the discharge elbow were not sufficient to evacuate the liquid passing around the head shaft. ClydeUnion Pumps therefore proposed a solution that would address this original issue as well as repairing the point of failure. The solution was to re-design the discharge elbow and separate it in two parts: the elbow itself, above the support surface, and a suction spool under. ClydeUnion Pumps redesigned the upper section with vanes to make it stiffer than before and incorporated a new salvage pipe in case of leakages. The lower, suction spool section has been made as a single piece part to increase its solidity. The former three gland ring outlets have been replaced by one, and the liquid pumped is passed by five holes that represent an area equivalent to the former version. To prevent corrosion, the bearings were also upgraded to a material with superior wear and abrasion characteristics, plus better chemical compatibility.

OUTCOMES

The pump has been operating well since the upgrade. The change of bearings material has eliminated abnormal wear and reduced the MTBF from less than one year to in excess of three years.