Evans Pump Station-#1 Pump and Motor Rebuild
Following the decision to rebuild the Evans pump #2 in 2021 for mechanical wear issues, but unexpectedly discovering severe cavitation damage to the propeller and diffuser housing it was decided that all three remaining Evans pumps need to be visually inspected for the same damage. During this investigation, it was discovered that cavitation was affecting all the pumps to varying degree, but that the cavitation had possibly damaged the Evans #1 pump to the point of unrepairable. Cavitation pitting was prevalent on 360 degrees of the diffuser housing, in some areas it had bored completely through the housing wall to the extent that you could visually see the propeller through the sidewall of the pump.
In early 2022 the SDIC board decided to repair the Evans #1 pump and motor. In September 2022 the Evans #1 pump and motor was was removed and sent out for repairs. The motor went to Reed Electric in Portland, OR and the pump to Bay Valve in Longview, WA.
Once the pump was disassembled and the diffuser housing was sandblaster, the severity of the cavitation damage was seen.
After much investigation, it was determined that the diffuser housing could be repaired. It would be much more cost effective, but it would be challenging and take time. The repair to the diffuser housing would require multiple stages. The process started with using a buildup of Belzona 1111 Super Metal resign epoxy to fill the cavitation pitting to standard internal diameter propeller clearance.
After curing, the Belzona 1111 was then machined down several thousandths of an inch and replaced with Belzona 2141 ElastoMeric Resign to give a layer of cavitation protection.
The diffuser housing was then externally wrapped with a Belzona Super Wrap II carbon fiber integrated mesh and epoxy to reinforce the weakened structure.
Along with the diffuser repair, the propeller was brazed in several areas for cavitation pitting and was rebalanced.
Different from the Evan's #2 pump and motor repairs in 2022, most of the internal pump stainless steel shafting had to be replaced; only the head shaft was reusable. The pump and motor was reassembled and reinstalled in February 2023.