Cvärde

cvärde, in Swedish technical usage, refers to the flow coefficient often called the CV value in valve sizing and process control. It is a parameter that characterizes how much fluid can pass through a valve for a given pressure drop, and it is most commonly expressed for liquids such as water.

Definition and purpose

A cvärde represents the valve’s capacity to pass fluid. In practice the CV concept links the flow rate through a valve to the pressure drop across it. A higher cvärde indicates a valve with greater flow capacity for the same pressure difference. The term is typically encountered in catalogs, datasheets, and specifications produced for process industries, plumbing, and HVAC where precise valve sizing is important.

Units and related concepts

In many Swedish and international contexts, CV is expressed as the flow rate in US gallons per minute (GPM) that will pass through the valve with a 1 psi pressure drop (for liquids like water at standard conditions). In metric contexts, Kv is used, which measures the flow rate in cubic meters per hour that passes with a 1 bar pressure drop. Cv och Kv are related concepts, and conversion between them is standard in engineering practice, depending on the fluid and condition.

Measurement and usage

Cv-values are typically provided by valve manufacturers and are validated under defined test conditions. When sizing a valve, engineers select a cvärde that meets the required flow rate for the process at the expected pressure drop, taking into account fluid properties, temperature, and viscosity. The actual flow will vary with operation, valve position, and fluid characteristics.

Applications and considerations

Cv-values are used across process industries, water treatment, and building services for valve selection and control system design. For fluids other than water or for gases, appropriate correction factors or alternative coefficients are applied. Proper understanding of cvärde supports reliable control, energy efficiency, and system safety.

See also: flow coefficient, valve sizing, Cv, Kv, ANSI/ISA standards.