• Ball Valves were a welcomed relief to the process industry. They provide tight shutoff and high capacity with just a quarter-turn to operate. Ball valves are now more common in 1/4"-6" sizes. Ball valves can be easily actuated with pneumatic and electric actuators.
  
  
• Butterfly Valves have come a long way from the old damper valve days. Today's butterfly valves are designed for general as well as severe service applications. Resilient liners provide tight shutoff in general service applications. Triple offset metal seated butterfly valves are designed for severe service applications. Butterfly valves are the most economical valves per comparable capacity and are easily automated with pneumatic and electric actuators.
  
  
• Float Valves automatically control liquid level and prevent overfilling tanks. The valve is operated mechanically by a float which rests on the top of the liquid. As the liquid level rises, it pushes the float up and closes the valve. As the level falls, the valve opens. The amount of liquid pressure the valve can shutoff against is determined by the length of the rod and size of the float for a given valve size.
  
  
• Gate Valves have a sliding disc (gate) which reciprocates into and out of the valve port. Gate valves are an ideal isolation valve for high pressure drop and high temperature applications where operation is infrequent. Manual operation is accomplished through a multi turn handwheel gear shaft assembly. Multiturn electric actuators are typically required to automate gate valves, however long stroke pneumatic and electro-hydraulic actuators are also available.
  
  
• Globe Valves have a conical plug which reciprocates into and out of the valve port. Globe valves are ideal for shutoff as well as throttling service in high pressure drop and high temperature applications. Available in globe, angle, and y-pattern designs. Manual operation is accomplished through a multi-turn handwheel assembly. Multiturn electric actuators are typically required to automate globe valves, however linear stroke pneumatic and electro-hydraulic actuators are also available.
  
  
• Plug Valves are similar to ball valves except instead of a spherical element, a cylindrical element is used as the internal restriction. Plug valves are typically more expensive than ball valves, but they are inherently more rugged as well. The plug is guided by a sleeve which acts as the sealing member. Plug valves require more torque to operate than ball valves, but are easily automated with quarter turn actuators. Plug valves are also available in 3-way and 180º configurations.

Pressure/Temperature Rating: The process fluid's combined pressure and temperature must be within the manufacturers published rating for a given valve. The given rating will be unique to a given body shell, body and trim material combination, seal material, and end connections. Select a rating that insures these combinations are sufficient to handle the maximum possible process conditions.

• Body Materials: Select body and trim materials based on their strength (pressure/temperature rating) and resistance to corrosion and erosion of a given process fluid. Plastic is used on very low pressure systems where corrosion is of primary concern. Brass/bronze is very economical and fairly corrosion resistant. Iron is very cost effective and can be economically coated or lined for compatibility with corrosive fluids. Select carbon steel where strength is needed. Stainless steel has very good strength and corrosion resistance. Other exotic alloys and molys can be supplied where needed.
  
  
• Seal Materials: Further select elastomeric and plastic seals, liners and diaphragms based on their chemical compatibility to the process fluid. Elastomeric elements (natural and synthetic rubbers) have better sealing characteristics, however plastics (PTFE, PFA, etc.) are typically chosen for harsh chemicals. Refer to chemical resistance guides for proper selection.
  
  
• End Connections: Valve body end connections are typically chosen based on initial cost, plant standard, and/or maintenance preference. Maintenance consideration is the preferred method of selection. Threaded ends (NPT/screwed) have a low initial cost, but are subject to leak paths and stripping. Use threaded ends where maintenance is not a concern. Welded ends provide for rigid, leak tight connections. They have low initial hardware cost, but high maintenance cost should they need to be cut out of the line for repair or replacement. Flanged ends have the highest initial cost, but are preferred from an installation and removal standpoint. Wafer bodies give the benefits of a flanged installation with very low initial cost. Use wafer bodies only where the pipe is rigid or fully supported. 3-Piece ball valve designs give the benefit of threaded or welded joints with integrally flanged wafer bodies.