The critical pressure is the vapor pressure of a fluid at the critical temperature above which distinct liquid and gas phases do not exist. As the critical temperature is approached, the properties of the gas and liquid phases become the same, resulting in only one phase.
The internal parts of the valve body, valve stem, valve seat, packing set, valve plug, gasket, etc. are collectively referred to as valve trim. In other words, all wetted parts that can be disassembled and replaced in the valve body are part of the control valve trim.
A choke valve is a type of control valve that has a restriction orifice that is used in oil and gas production wells to control the flow of good fluids being produced.
Incipient cavitation represents the beginning stage of cavitation where light popping noises are heard. Constant cavitation is a steady rumbling sound associated with the start of possible valve damage.
There are many process parameters that should be provided for the sizing of control valves. Here just examples of parts of the most important data for your reference.
Generally, the terms rangeability and turndown ratio are associated with control valve sizing and flow measuring devices.
Theoretically dropping high pressure across two valves is better than one valve. However, in practice, two valves will not usually control well together unless the process can operate with a very low proportional band with a slow response time.
Noise is created by an object vibrating. The control valve components will tend to vibrate whenever they are subjected to high-velocity turbulent flow.
Inherent characteristics are the flow through the valve (or CV) relative to the percentage opening (the pressure drop at both ends of the valve is constant) of the graph. This is the result of a workshop test in which the upstream and downstream pressures are constant and the only variables are the flow and opening of the valve.
The most common features are shown in the figure above.The percentage of flow through the valve corresponds to the stem position.These curves are based on a constant pressure drop across the valve and are known as the inherent flow characteristics.
The inherent flow characteristic of the control valve is the relationship between the flow and travel of the valve to a constant pressure drop across the valve.
The Venturi desuperheater adopts restrictive measures in the superheated steam pipeline to form a high-speed and turbulent area where cooling water is injected. This helps to establish close contact between steam and cooling water, thereby increasing the efficiency of the desuperheating process.