Des Moines Water Works’ 30-year-old backflush valve was leaking and needed to be replaced. The backflush valve is an integral part of a filter cleaning system to allow the required periodic cleaning of 16 sand-gravel filters. Without a functioning backflush valve and cleaning system, the filters will operate for a limited time before plant operations need to be shut down.
Baker Group was awarded the project to replace the 2,600-pound valve, which required meticulous planning, prefabrication of special tools and a spacer, plumbing, piping and absolutely reliable execution.
“Time critical” assignment
Michael J. McCurnin, P.E., Director of Water Production for Des Moines Water Works, describes the project: “From an operational perspective, DMWW and Baker Group teamed up to perform an extremely time critical ‘remove and replace’ effort of a large butterfly valve in our backwash header system. The state’s largest water treatment plant was without a filter backwash system during this process. This creates time constraints, that if not followed create public water supply issues for 500,000 central Iowans. With such narrow time constraints, the stakes were extremely high.”
Extensive planning and preparation
“We had our Mechanical Engineers, Structural Engineer and Prefabrication teams all on the task months in advance. I cannot overemphasize the prep work that went into this,” says Jim Fetters, Baker Group Project Manager.
To prepare for the February 17, 2017 valve replacement, Baker Group’s Mechanical and Prefabrication teams:
- Designed and fabricated special tools. The ceiling height prohibited removing the backflush valve using conventional means, such as a gantry, chain fall or crane. To facilitate removal, Baker Group designed and engineered a tool that would fit onto a forklift and slide underneath the valve, which would then carry the valve out of and into the space. Baker Group also designed and fabricated temporary supports to hold up existing piping and fittings during the valve replacement to ensure the safety of workers.
- Retrofit the valve. The new, manufactured valve was ¼-inch shorter than the old one. A washer-like spacer with 36 precisely placed holes for bolts – some with threads – was designed, fabricated and tested in advance. “It worked perfectly,” says Fetters.
- Removed rusted-on bolts in advance. Loosening and removing the 72 rusted-on bolts would be a time-intensive task. Realizing this the Baker Group team removed and replaced the bolts in advance.
Preparation pays off
When February 17, 2017 came, Baker Group’s Mechanical team – three plumbers and one equipment operator – worked around the clock to replace the valve. In eight hours, less than the allotted 36 hours, Des Moines Water Works’ filtration system was again operational. Des Moines’ water supply never faltered. “Nick Lause, our foreman who led the crew, was absolutely key to the success of this project,” Fetters adds.
Tony Knox, Water Production Maintenance Manager with Des Moines Water Works, says, “The planning, preparation and execution demonstrated by the Baker Group team showed a high skill level and professionalism that only a few have to complete such a critical task in a confident and timely manner.”
McCurnin adds, “Baker Group delivered in a most confident and competent manner. It was a pleasure to have their expertise within our treatment facilities before and during the day of the valve replacement.”