The Bull Run dam in Portland, Oregon.
The Portland Water Bureau (PWB) has developed the Bull Run Water Supply Habitat Conservation Plan (HCP) to make the necessary changes to the City's drinking water operations and help the aquatic environment improve for fish stock. Part of the HCP is a water temperature management plan to comply with the Clean Water Act, a critical component in the rehabilitation of the fish stock.
The problem was that the water temperature of the Sandy River during summer months was too warm, making it difficult for the fish to spawn. The reason the river got too warm was because the source of the river water is pulled from the top of the reservoir, which is warmer. The PWB consulted with an engineering firm to come up with a plan to regulate temperature. The idea was to supply the river with water from the bottom of the reservoir where the water would be significantly cooler. Using temperature readings at several points down the river, they could control the river water temperature by controlling the amount of cold water that was feeding into the river.
Control valve system
In order to make this happen they needed a distribution system that would control the amount of cold water entering the system by setting a desired flow rate of cold water. The control system would need to have the capabilities of measuring flow as well as have the capacity to flow from low flows to upwards of 83000 gpm to make this possible. As the reservoir fill height has an inlet pressure of 45 psi and the water is going into the river at atmospheric pressure, the valve control system also needed to have the capabilities of withstanding a 45 to 0 psi pressure drop. This is when CIMCO, suppliers of waterworks products, brought in Singer Valve to design a control valve system that could handle these stringent requirements.
36 inch 2SC-PCO-MV-C-AC in the process of being commissioned by Singer and Cimco Staff.
The solution from Singer was to supply a S106-2SC-PCO-MV-C-AC valve and an MCP-TP Control Panel. This valve has dual solenoids in the pilot system, which allows the MCP-TP to control the valve and modulate the valve to the required set points electronically. The valve is equipped with backflow check to ensure the valve closes in the event of reverse flow. Due to the maximum flow requirements, a 24 inch and 36 inch valve were enough to manage full flow variance. Additional features offered on the valve were the Single Rolling Diaphragm (SRD) and Anti-Cav.
The pressure drop of 45 psi to 0 would definitely cause a valve to cavitate, creating a lot of noise, vibration and eventual deterioration to the internals of the valves. Usually cavitation is avoided by installing multiple pressure reducing valves in series, which knocks down the pressure to controllable levels. Steve Causseaux, sales manager for CIMCO said: “The beauty of Singer's anti-cav technology is that it is contained in the valve itself, so no additional valves are needed, saving money, time, and future maintenance.”
The Anti-cav is comprised of two heavy stainless steel sliding cages that maximize the full flow capacity. The first cage directs and contains the cavitation recovery, allowing it to dissipate harmlessly, while the second cage allows further control to a level as low as atmospheric pressure downstream. The cages are individually engineered by entering the data into proprietary software which calculates the size and placement of the orifices on both inlet and outlet cages. The valve bodies are specifically designed to fit a larger cage allowing higher Cv values (increased flow) while also allowing for reasonable space between the anti-cavitation trim and the body wall. This separation allows for consistent uniform entry around the cage area ensuring the vapour bubbles collapse symmetrically towards the center of the anti-cavitation cage.
36 inch Singer valve and staff from the Portland Water Bureau being trained on the electronics MCP Panel that was supplied.
The range between a high flow of 83,000gpm and low flows would typically require a large valve for the high flows and smaller valves to handle the lower flows as traditional valves become inefficient at low flows and start to hunt and chatter. To overcome this challenge, the valves were equipped with the SRD technology. The SRD moulded diaphragm provides a constant surface area no matter the valve position and avoids injecting small pressure pulses into the piping. By doing this, the valve eliminates seat chatter at low flows helping to prevent water loss and leakage while providing smooth, precisely controlled flow.
The 24 inch and 36 inch valves were set to run in parallel and the controls were consolidated into one panel to save on space and costs. Singer electronics division designed and built a control panel to receive information from both valves and have the ability to control the valves individually. Using a differential transmitter and a valve position indicator from each valve the MCP Panel is able to calculate the individual flows through each valve. This allows the PWB operators to control the valves to specific flow rates by entering a setpoint into the panel or remotely via SCADA. The panel then sends signals to the opening or closing solenoid valves to open or close the main valves until they meet their desired flow rates.
The panel also needed to be able to handle a main power loss so the addition of a UPS battery backup was added. To withstand the outdoor environment, the panel has an outdoor rated enclosure with a heater and dehumidifier to keep the panel dry. The customized panel was seamlessly fitted into the existing SCADA system making it simple for the operators to enter desired flow rates from a remote location.
“The ingenuity in overall concept and design was matched with Singer's ability to customize a valve to meet some difficult parameters,” said Andrew Degner, water treatment operations manager for the Portland Water Bureau. “I am pleased to say that we have achieved what we set out to with a fail proof solution that is easy to manage and maintain.”
Authors: Clint Smith & Ryan Spooner, Singer Valve.