The Biggest Valves: Sizes Growing in Step with Greater Demand
Mueller Water Products is a manufacturer and marketer of products and services used in the transmission, distribution and measurement of water. For more than 160 years, Mueller has manufactured a variety of valves, including large custom-engineered valves. The company’s broad product and service portfolio also includes fire hydrants, pipe connection and repair products, metering products, leak detection, pipe condition assessment and pressure management products.
Why is there a trend toward producing bigger valves?
The frequency and severity of drought in the West and severe weather events, like slow-moving hurricanes in the gulf and on the East Coast, have motivated municipalities to creatively figure out how to collect, protect and conserve available raw and semi-finished freshwater resources. The large population migration to non-drought areas and the numerous water conservation projects in drought-ridden regions are fueling some very large projects, such as protectively “banking” water that has already been treated in new facilities. There are also big projects underway to prevent raw water reservoirs from overflowing to the south. To do this, new or larger pumping stations are being built to pump (transfer) water over to neighboring northern reservoirs to minimize losing what has already been naturally collected. Moving larger amounts of water requires bigger valves.
What are the most significant challenges in dealing with exceptionally large valves?
One of the biggest challenges is costing and pricing. Due to the seldom-sourced large-diameter product, the ability to accurately estimate the cost to produce these sizes is a big risk for manufacturers — the work is often too large to machine in-house, so the outsourced production becomes an unknown cost variable, which is a gray area in getting a fixed or capped cost. The same goes for the raw materials. These projects are sometimes years out, so the cost per pound of carbon steel and stainless alloys can swing in the wrong direction over the course of the project. Also, any ancillary (one-time) equipment costs need to be taken into consideration, such as testing equipment (test heads with bolts and nuts). The costs are high and the lead time alone to obtain a pair of large-diameter test heads can be up to 18 months. Another challenge is that when you are dealing with large castings you have more room for casting issues, like porosity. Also handling and testing becomes more complicated as valves get larger.
Are your largest valves all “one off” or custom-made?
Yes. Anything that is not covered by a nationally recognized standard (or designed to the intent of a standard) is considered a custom product. For both butterfly and plug valves, we have large standard castings, but we have also fabricated large butterfly valves.
Mueller Case Study: Valve and Actuator Updates for Aging Reclamation Plant
The Hyperion Water Reclamation Plant is the largest sewage treatment facility in the Los Angeles metropolitan area, treating 450 million gallons per day. During a comprehensive inspection, Hyperion officials discovered deterioration of its primary outfall pipeline, which wasn’t unusual given that the pipeline and pump header were over 60 years old. The inspection also revealed that 10 old isolation butterfly valves on the suction and discharge sides of the vertical turbine effluent pumps needed to be refurbished or replaced due to corrosion of the valve body and disc. When tide and plant hydraulic conditions allow, plant effluent flows with the help of gravity through a 120-inch diameter butterfly valve (Figure 12) to the plant’s five-mile outfall pipeline without the use of pumps. Failure of any of these valves could create a backflow event, which would flood the plant.
To repair the pipeline, maintenance and construction crews needed to divert the treated wastewater to an emergency one-mile outfall pipeline. The city’s environmental engineering division determined that Hyperion crews and suppliers would need to work around the clock for six weeks to minimize impact on plant operations and the environment.
While refurbishing valves can save money, it can often take longer than installing new products. Existing valves must be inspected to determine if refurbishment is a viable option, and given the location, these valves could not be extracted until the project had begun. This would delay the project’s timeline, as parts would need to be located and ordered when work should already be underway. The Los Angeles Department of Public Works had documented that the five existing 60-inch butterfly valves and the five 78-inch valves were Pratt valves installed in the early 1970s. Knowing this information meant original project files, parts and replacement valves could be on hand before starting the work.
However, there was one exception: the 120-inch gravity-fed butterfly valve was critical to public safety and plant operations. If this valve were to fail in the open position at high tide, ocean water from the bay and effluent would back up the pipe and potentially flood the facility. There was no secondary valve, but rather a redundant cylinder for closing and opening the valve. This butterfly valve was custom-made with no original manufacturer marking to be found. Given the time constraints, replacing it with a new butterfly valve was the only viable option. This also meant that a new actuation system would be required.
Moog Flo-Tork designed an actuator that required 3,200 cubic inches (13.9 gallons) of hydraulic oil per stroke with a rated working oil pressure of 3,000 psi. This system would produce up to three million inch pounds of torque from either one of the two rack-and-pinion actuators, which accommodated the need for redundancy. Even though the two actuators are mechanically sandwiched together, they act as independent primary and emergency backup actuation systems.
Click here to read the article in Valve Magazine on Pg 22