Nicholson Steam Trap has introduced butterfly valves, check valves and fabricated strainers that are suitable for a variety of commercial applications. The new butterfly valves are available in cast iron with stainless steel shafts, in sizes from 2" through 48". A special phenolic-backed seat is utilized to prevent seat collapse and provides a primary shaft seal. The check valves are available in cast iron, bronze, carbon steel and stainless steel in sizes from 2" through 30". A resilient seat is used to maintain a metal to soft seat seal in case of seat failure. The fabricated strainers are available with cast iron, bronze, steel or stainless steel bodies and a choice of screen areas. All screens are 300 series stainless steel for long life. Nicholson Steam Trap.