Recirculation valves.

Three-way recirculation valves use a stainless steel disk that rotates 90o to switch the fluid flow from the recirculation port to the discharge port. The disk and its mating port block are hardened stainless steel. Sealing pressure between the disk and mating block is provided by a spring riding on a ball thrust bearing. The actuator shaft is also hardened stainless steel and is sealed with a Teflon face seal. A valve will typically operate 10 to 40 million cycles before adjustment or maintenance are required (based on non-abrasive fluids). The company routinely uses these valves with dispensing equipment running several thousand parts per day and cycle times shorter than one second. Minimum air entrapment and fast response are said to eliminate lead/lag in the valves to allow production rates that can exceed 80,000 parts per day. Heat tracing ports are said to make the valve easy to use for high temperature applications and materials with high melting points, such as MOCA (216[degrees] F/102[degrees] C) and XA (210[degrees] F/99[degrees] C). Connections are made to the valve with small, two-bolt manifold blocks. These blocks connect both the material and heat tracing line to the valve body. General maintenance is said to be easy. The Teflon shaft seal will typically run 20 million cycles before requiring adjustment, and 40 million cycles before requiring replacement. Through proper care of the internal parts, the valve's metal parts should last in excess of 200 million cycles, according to the manufacturer. Applications include urethane processing. (Max Machinery, 1420 Healdsburg Ave., Healdsburg, CA 95448) Circle 35 on card