What is the Cv of a globe valve?
Cv is the volume of water in U.S. gallons per minute that passes through the valve at a pressure drop of 1 PSI at 68°F.
How is flow rate determined in globe valves?
In globe valves, flow rate is determined by the lift of the valve plug from the seat. Manual globe valves can have equal-percentage, linear or quick-opening flow.
How do you size a globe valve?
As a guide, correctly sized globe valves are typically one size smaller than the line size and properly sized butterfly, full-ball and segment-ball valves are typically two sizes smaller than the line size. Note, this statement should be used as an indicative guide only and not as design criteria or a design rule.
How do you calculate the flow coefficient of a valve?
The equation for calculating the valve flow coefficient is Cv = Q √ (SQ/P).
How do you calculate Cv value?
The formula for the coefficient of variation is: Coefficient of Variation = (Standard Deviation / Mean) * 100. In symbols: CV = (SD/x̄) * 100.
How do you use Cv flow coefficient?
In the U.S. system of units, the Cv coefficient is the number of U.S. gallons per minute of water that will pass through a given orifice area at a pressure drop of 1 PSI. An orifice or valve passage which has a Cv coefficient of 1.00 will pass 1 GPM of water (specific gravity 1.0) with a pressure drop of 1 PSI.
How do globe valves work?
A globe valve is primarily designed to stop, start and regulate flow. When the handle is turned, manually or through an actuator, a disc is lowered or raised by means of the valve stem. When the disc is fully lowered, the fluid flow is shut off.
What type of valve is a globe valve?
A globe valve is one of the most common types of control valve. Globe valves have sphere-shaped bodies. Inside the valve, a baffle separates two halves. This internal structure creates a different flow path than ball valves and other rotary-type valves.
What is valve sizing coefficient?
Valve Flow Coefficient (Cv) is the flow capability of a control valve at fully open conditions relative to the pressure drop across the valve. It is defined as the volume of water (GPM in the US) at 60°F that will flow through a fully open valve with a pressure differential of 1 psi across the valve.
How is Cv calculated?
Formula. The formula for the coefficient of variation is: Coefficient of Variation = (Standard Deviation / Mean) * 100. In symbols: CV = (SD/x̄) * 100.
What is the class and size of a globe valve?
Bolted Bonnet Globe Valves API 623 & B 16.34 Class: 150 – 2500Size: 2” – 18” The Flow Coefficiency (Cv) of a valve is the rate of gallons per minute of water at 60° F through a fully opened valve at a pressure drop of 1 PSI across the valve.
How is the flow rate of a globe valve determined?
Flow rate is affected by the flow characteristic and the pressure drop across the valve. In globe valves, flow rate is determined by the lift of the valve plug from the seat. Manual globe valves can have equal-percentage, linear or quick-opening flow.
How does a globe valve work?
When the globe valve is open, the fluid flows through the space between the edge of the disk and the seat. The flow rate for the media is determined by the distance between the valve plug and the valve seat.
What causes head loss in a globe valve design?
While head loss is unavoidable in fluid systems, it is increased by obstructions and discontinuities in the flow path such as the S shape of the globe valve design. The body and flow pipes are rounded and smooth to provide system flow without creating turbulence or noise.