Types of Rising Stem (multi-turn) Valves Gate Valves A gate valve functions by moving a wedge shaped disc obstructer up and down to open and close the flow path through the valve. This linear motion is provided by a threaded rising stem. Turning this threaded stem requires multiple revolutions (multi-turn) to travel from open to closed. The number of revolutions required is usually the valve size in inches x 3 + 2. So a 6 inch valve will require 20 turns of the stem [(6 x 3) + 2 = 20]. They should only be used for on/off applications as throttling for an extended period of time will damage both the obstructer and seals. Use of a gate valve for throttling is also not very effective since most of the reduction of flow will increase in the last 10% of closure. Globe Valves Globe valves operate by having a convex disc shaped plug raise and lower via a rising stem into a circular seat around the inside of the globe shaped body at the “equator”. The flow enters the “lower hemisphere” from

  Types of (Quarter-turn) Rotary Valves Ball Valves Quarter-turn 2-way ball valves are by far the most common type of process control valve. They are 2-way (inlet and outlet), 2-position (open and closed) valves that are used for shut-off or isolation of a system, or a loop or component within a system. The basic construction of a ball valve includes a ball as the obstructer which is sandwiched between two cup shaped seals referred to as “seats”. Typically the ball has a bore straight through it. Media flows through this bore when the valve is open. When the ball is rotated 90˚, the flow of media is stopped by the sides of the ball which now completely fill the opening in the seats. Plug Valves The basic construction of a plug valve is practically identical to that of a ball valve with the exception of the shape of the obstructer used. In this case, the ball is replaced by a slightly tapered cylinder. This cylinder has a bore through it just like a ball valve, and it operates the same

  Types of Valves Rotary Valves These types of valves rely on the rotary motion of the flow obstructer In most cases this rotation is limited to 90 degrees (one quarter-turn), however, there are valves that operate using a larger degree of rotation and have more than 2 positions that are used in regular operation. Valves that are truly quarter-turn are completely closed at 0˚ and completely open at 90˚. Examples of quarter-turn valves are ball valves, plug valves, and butterfly valves. Linear Valves There are 2 distinct types of linear valves: rising stem (multi-turn) and axial. While both valve types rely on the linear motion of the flow obstructer, they are very different in construction and operation. Multi-turn rising stem valves move the obstructer by the rotation of a threaded rod (stem) which is attached to the obstructer Examples of multi-turn valves are gate valves, globe valves, pinch valves, diaphragm valves, and needle valves. These valve types are commonly used for flow co

Control Valves A control valve is a valve and basically a control valve is used to control the fluid flow by changing the shape of the valve. And is basically the final control element known as the control valve and is used to regulate or control the fluid flow of the pipe or flow channel. and controls or regulates fluid pressure, temperature, and fluid volume. A control valve is a power operated instrument and basically a control valve controls the fluid flow rate in a process control system. Basics of Control Valves Valves are used for thousands of purposes, from simple and mundane tasks like turning on the water in a kitchen sink to important and difficult tasks like controlling the flow of water through a nuclear reactor. Valves are basically important for controlling the flow of liquids and gases in daily life. Some valves are used to isolate the system, shut off system pressure, and/or for vacuum maintenance and repair. Others are used to reverse or throttle the flow in the syste