River water is an efficient and ecological coolant for industrial cooling distribution networks. However, the large volumes of water that must pass through the heat exchanger or chiller in the coolant production cycle require a low pressure drop and consistent flow levels. To accomplish these tasks, equipment must be selected to create the least possible resistance.
When one cooling production plant in France was designing its new coolant distribution system, engineers paid special attention to the valves. Many cooling operations that use river water as the cooling medium use mechanical check valves to control flow. Unfortunately, mechanical check valves have moving parts that typically result in high maintenance costs as well as a higher pressure loss than desired. For the new installation, the goal was to eliminate these problems and find a solution that would provide quiet, smooth operation with a pressure drop of less than 1.5 psi (0.1 bar).
After evaluating several options, engineers chose the Stop-Silent check valve produced by Lasso Technik Inc., Basel, Switzerland, because it was able to achieve the required low pressure drop of 1.5 psi. The valve is constructed without movable mechanical parts and consists of only two components - a perforated stainless steel cone and a rubber membrane. When the valve is in the open position, the diaphragm deflects inward (figure 1, upper half). This movement allows passage of the coolant (in this case, river water) with minimal pressure loss. When the valve closes (figure 1, lower half), a backpressure condition allows the diaphragm to resume its relaxed position, covering all apertures in the cone and creating a tight shutoff.
Challenges integral to installation success at the plant included positioning the cones to secure the lowest possible pressure drop and using pumps that require less power. To accomplish these goals, the body shape of the valve was custom-designed to optimize the flow characteristics (figure 2), and six multi-cone valves were installed. Each multi-cone valve consisted of the valve body with 42 single valves (cones and diaphragms) inside (figure 3) to ensure flow rates. The body was welded together and covered with an epoxy coating. Engineers optimized the layout of the pipes, pumps and heat exchangers to handle an operating pressure of 44 psi (3 bar) with an operating temperature range of 41 to 82°F (5 to 28°C) and speeds of 13,860 gal/min (875 l/sec). Implementing the multi-cone valve resulted in a pressure drop of 1.3 psi (0.09 bar).
The valve’s cone design combined with an optimal site layout minimized the pressure drop to the system, thereby achieving one of the major goals for the installation. Because the valve does not have moving parts that can wear, the plant expects it to provide maintenance-free service for up to 10 years. The valve also eliminated water hammer and associated problems, thereby providing nearly noise-free operation, along with the ability to function simultaneously as a filter. No special training was required other than the installation instructions, and the plant’s expectations were fulfilled.
As plants continue to look for ways to increase cooling efficiency and reduce maintenance requirements, new valve options will play an increasingly important role in helping to achieve these goals. PC
For more information about the cone-shaped valves, contact Great Western Supply Co., Houston, Texas, (713) 681-4786, e-mail Harry Boudreaux at email@example.com, or visit www.stopsilent.com.