Power Zone overhauled a 4000 horsepower 7 stage descaling pump for a steel mill in eastern Europe. The mill had three 50% pumps and was in its 5th month awaiting repair in the shop of a major pump OEM. When the second pump suffered major vibrations, they were forced to operate at a reduced output and needed the second pump repaired quickly. Power Zone accepted one of its most challenging equipment rebuilds yet, returned the pump to the customer in just 10 weeks.
The pump was a classic basket case. The first impeller was broken and the wear rings had been stripped off. Pieces of the first and second stage wear rings were found lodged in the next 4 impellers. The interstage piece between the first and second stage impeller was similarly destroyed, taking its saddle fit in the casing with it. The pieces lodged in the first impeller caused severe cavitation, which removed about an inch and a half of material from the cutwaters. An 8 square inch piece of the shroud on the 5th impeller had broken out. The shaft was bent, and the bearing housings were warped.
Damaged impeller and missing wear ring
We had new impellers cast for the 1st and 5th impellers, made a new shaft, replaced all the impeller rings, re-machined the case rings, replaced the shaft mounted lube oil pump, made a new interstage piece, new throttle, and center bushings, and repaired the throttle and center sleeves. Add new packing sleeves, weld repair the cutwaters and casing saddle fits, clip-and-bore the casing and bearing housings, balance the rotor, and the pump was re-assembled.
Broken impeller as a result of catastrophic pump failure
And then we put it on our test stand and ran it, developing the full performance curve with power draw, efficiency, and NPSH curves included. 10 weeks after receiving it, we crated the pump up and returned it to the (very happy) client. Then we assisted in the on-site re-commissioning of the pump a few weeks later. The first pump was still at the OEM repair shop 7 months after our pump was placed into service.
One of several re-cast impellers for the rebuilt pump