Valves are for starting or stopping flow, regulating or throttling flow, preventing back flow or relieving and regulating pressure in fluid or gaseous handling applications. Common valve types include: Ball,Butterfly,Check, Diaphragm, Gate, Globe, Knife Gate, Parallel Slide, Pinch, Piston, Plug, Sluice, etc.
Ball valve
Ball valve like Cast Steel Y Strainer carries a spherical plug. The spherical plug is really a controlling element. They are traditionally used in chemical process industries. It is used where throttling and disconnect combination is necessary. It offers good flow characteristics. Ball valve includes a two way globe plus the ball rotates between resilient seats. It is compact and needs low maintenance without lubrication. It is accessible in venture pattern, reduced and full port patterns. By giving 1 / 4 turn to the ball, the valve may be closed or opened. The valve won't give good throttling. It can be obtainable in size from 6mm to as huge as 900mm. It may be used for pressures upto 500 kg/cm and temperature upto 300°C.
Butterfly valves
Butterfly valves can be simple but very versatile. Just like the ball valve, butterfly valves are quarter-turn operated valves that happen to be mostly found in many industries along with a wide range of applications. Its quarter-turn element ensures quick operation in the valve.
The globe valve is acceptable for use on the wide variety of applications, from flow rate control to open/close operation.
In such a valve, flow rate control is established not with the size on the opening inside valve seat, but rather through the lift in the valve plug (the space the valve plug comes from the valve seat). One feature of globe valves is always that even if used inside the partially open position, there is certainly less likelihood of damage to your valve seat or valve plug with the fluid as compared to other kinds of manual valves. Among the various configurations available, needle type globe valves are particularly suitable for flow rate control.
Other considerations about globe valves is the pressure drop throughout the valve is higher than that of many other valves since the passageway is S-shaped. Valve operation time is usually longer as the valve stem have to be turned many times in order to open and shut the valve, and this also may eventually cause leakage on the gland seal (packing).
