What is the difference between installed and inherent characteristics?
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.
Definition of linear and equal percent characteristic?
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.
Why Do Different Control Valves Have Different 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.
What is a desuperheater and how does it differ from an attemporator?
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.
What is Difference Between Liquid, Vapor, and Gas?
In general, a vapour phase consists of a phase with two different substances at room temperature, whereas a gas phase consists of a single substance at a defined thermodynamic range, at room temperature.
What is the Critical Flow Factor in Control Valve Critical?
Critical Flow Factor often referred to as “Cf” is a coefficient that defines how pressure will recover after it drops to its lowest point inside the control valve.
How can cavitation damage be contained?
Cavitation is common, so many control valves can withstand a certain amount of time. However, prolonged exposure to cavitation can severely damage the control valve.
What is choked flow in control valves?
Blocking flow is defined as a point at which increasing the pressure drop (△P) while maintaining a constant inlet pressure (P1) will not result in a further increase in flow.
What is Flashing in Control Valves?
Flashing occurs when a liquid flows through a control valve and evaporates to retain the vapor. Flashing has some characteristics in common with Cho flow and Cavitation, I. E. The process begins with the vaporization of liquid near the Vena Cava. In order to treat the control valve application as a flash application, the downstream pressure must be less than the steam pressure (p 2 < PV) .
What is Cavitation for Control Valves?
Cavitation is the formation and collapse of vapor bubbles (cavities) in the liquid flow streams caused by changes in pressure and velocity. There are four primary negative side effects of uncontrolled cavitation in control valves: high noise, excessive vibration, material damage, and deterioration of flow effectiveness. Physical damage to valve trim is usually characterized by a pitted, rough appearance.
What is the difference between actual, standard, and normal flow rates for gases?
Standard flow rate is a correction applied to an actual flow measurement based on a given temperature and pressure. The correction is applied using the ideal gas law. The most widely used value is 1 atmosphere (101.3 kPa) or 14.696 psia at sea level and 59 0F (150C).
What is CV of Control Valves?
Control valve CV refers to the flow coefficient of the valve. It applies to the factor of the head drop (Δh) or pressure drop (ΔP) over a valve with the flow rate Q.
