Ball valve
When the operating temperature is between -29℃ and 200℃, most manual (open and close) ball valves are suitable for the operation of hydrocarbon and public systems. For ball valves used above 100℃, careful consideration should be given to the temperature limit of soft sealing materials above 100℃ when applying. In high temperature or severe abrasion operations, the application of metal sealed ball valves should be considered, but it should be noted that operating torque must be increased. Ball valves have two designs, the float ball and the trunnion ball valve. Float valves are designed to produce high operating torque at high pressures or large diameters, but are better sealed. Ball valves are not suitable for throttling because, when the valve is partially open, its sealing surface can be damaged by exposure to the handling fluid. For critical operations, consideration should be given to purchasing ball valves equipped with ball seat and stem lubrication fittings, as lubrication prevents slight leakage and reduces operating torque.
Gate valves
Gate valves are suitable in all temperature ranges for most switching operations, vibration-free hydrocarbons, and utilities. Gate valves may be opened or closed from their normal position during operation with vibration. Unless the stem packing is carefully adjusted, gate valves have better torque characteristics than ball and plug valves, but do not have the convenience of 90 degree rotation. For manually operated gate valves of size DN50(2in) or larger, flexible or expansion gates shall be provided. Wedge gate valves usually do not have cavity overpressure protection. Unprotected open stem gate valves are not recommended. The Marine environment corrodes exposed stem and thread, making the valve difficult to operate and easy to damage stem packing. Gate valve with reverse action plate for automatic shutoff system operation. Simple push-pull manipulators are available for these valves, thus avoiding the complex joystick cams commonly required for ball and plug valves. All movable parts of gate valves with power operators can be enclosed to eliminate contamination from paint and corrosion products. Gate valves shall not be used in throttling operations. Throttling can damage the sealing surface, especially for a fluid containing sand. The operating temperature of the soft-seal gate valve is limited by the sealing material.
Butterfly valve
General butterfly valves are suitable for rough throttling and low pressure, no hydrocarbon, no dangerous work, they are not suitable for containers, tanks, etc. Important shutoff valves. Non-linear butterfly valves should be used in operating conditions where the temperature is higher than 65℃ or the pressure level is higher than ASME150 or dangerous fluids. Since it takes only a small torque to vibrate the butterfly valve open, the handle should be equipped with a locking device.
