＞Rubber lined butterfly valves are a type of valve which can be used for isolating or regulating flow.
＞The closing mechanism is the disc which sits in the center of the valve body. The disc is connected to a handle or actuator via the shaft which passes from the disc through the top of the valve body.
＞Unlike a ball valve, the disc of the butterfly valve is always Present in the flow, which will induce the pressure drop.
＞Rubber lined butterfly valves operate in a quarter turn, meaning that rotating the closed disc 90° will fully open the valve, and vice versa. They can also be opened incrementally in order to throttle flow.
＞Compared with the ball valve, a butterfly valve can be shut off quickly but requires less support due to its lighter weight.
＞This can be accomplished manually, but throttling flow will be more precise when an actuator is used cooperatively.
＞Actuators can be customized to allow incremental flow, by using positioners in the case of pneumatic and hydraulic actuators, or by using modulating boards in the case of electric actuators.
＞Trunnion mounted ball valves are quarter-turn valves used to stop the flow of medium in pipelines. These valves feature a round or spherical disk in the center that rotates to start or stop the flow. This disk is called the ball and it features a hollow center.
＞Ball valves are extremely versatile and are commonly used in industrial applications where tight shut-off is required.
＞Trunnion ball valves feature additional support part for the ball. This support part is in the shape of a shaft and is called a trunnion. The trunnion absorbs any added pressure from the flow, reducing stress on the ball and valve seats.
＞Trunnion ball valves are used in high-pressure, large scale applications where low operating torque is required.
＞A Globe valve is a linear motion valve and is primarily designed to stop, start and regulate flow. The disk of a globe valve can be totally removed from the flow path or it can completely close the flow path.
＞Conventional Globe valves may be used for isolation and throttling service. Although these valves exhibit slightly higher pressure drops than straight-through valves (e.g., gate, plug, ball, etc.), they may be used in applications where the pressure drop through the valve is not a controiling factor.
＞Globe valves are extensively used to control flow. The range of flow control, pressure drop, and duty must be considered in the design of the valve to avert premature failure and to assure satisfactory service.
＞Valves subjected to high-differential pressure-throttling service require specially designed valve trim.
＞Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as control valves.
＞Operation of a gate valve is performed doing an either clockwise to close (CTC) or clockwise to open (CTO) rotating motion of the stem. When operating the valve stem, the gate moves upwards or downwards on the threaded part of the stem.
＞Gate valves are often used when minimum pressure loss and a free bore is needed. When fully open, a typical gate valve has no obstruction in the flow path resulting in a very low pressure loss, and this design makes it possible to use a pipe-cleaning pig.
＞A gate valve is a multi-turn valve, meaning that the operation of the valve is done by a threaded stem. As the valve has to turn multiple times to move from open to closed position, the slow operation also prevents water hammer effects.
＞Single seated valves are one form of globe valves that are very common and quite simple in design. These valves have a few internal parts. They are also smaller than double seated valves and provide good shut-off capability.
＞Maintenance is simplified due to easy access with top entry to the valve components. Because of their widespread usage, single seated valves are available in a variety of trim configurations, and therefore a greater range of flow characteristics are available. They also produce less vibration due to the reduced plug mass.
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