Wastewater treatment plants use davit cranes to raise and lower submerged mixers in biological aeration tanks when they are not in use or require maintenance. A common practice in larger plants is to mount bases wherever hoists are needed and use only one or two portable davit cranes do the lifting, moving them from station to station as needed.
While this is an excellent space and cost saving measure, some plants have discovered it creates an additional problem. At lift stations where the cranes are not in use extra wire rope is left with nowhere to be tied off or stored, creating hazard to operators and equipment.
When left laying near the lift stations the mess of excess wire rope creates a potentially dangerous obstacle for operators working around aeration tanks. If not tied off correctly the wire rope can easily slip into wet wells where it can cause significant damage to mixers.
At plants such as the new Eagles Point Wastewater Treatment Plant in Cottage Grove, Minnesota, where more than 24 wall and floor bases are installed at various lift stations and only two portable davit cranes are in use at any given time, the result is a lot of extra wire rope just lying around the biological aeration areas.
Tim Miller of Electric Pump was a supplier for the new plant and recognized the potential hazard immediately. He suggested to the plant owners and engineering firm that there must be a provision to eliminate the problem. The operators don’t have time to tie off the loose wire ropes appropriately so the solution had to be quick and simple.
As it happened, Thern’s newly developed RW50 Cable Spool was the perfect solution. The stainless steel reel winds up excess wire rope when it is detached from the crane, thus eliminating the mess and danger created by the loose cables.
From an operations and maintenance standpoint Miller believes the cable spools the plant installed at each lift station are ideal. They keep the cables tight, secure and out of the way, are simple to use and the operators love them.
Additionally, Thern’s RW50 Cable Spools are constructed of durable stainless steel with an electro-polished finish for superior corrosion resistance. Like all Thern products, RW50’s are built for long-lasting, reliable performance in any environment.
The Eagles Point Plant began service in September of 2002, replacing an existing plant that had been in operation since 1962. The new plant has the capacity to treat 10 million gallons of wastewater per day and currently serves a population of 28,000. It provides both primary and secondary treatment before discharging it to the Mississippi River.
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