Various Calculation Tools

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Various Calculation Tools are available for practical use.

Unit Conversion

Absolute pressure and gauge pressure can be converted in the pressure unit. Gas flow rate can be converted between the actual flow rate and normal flow rate.
Viscosity and kinematic viscosity can be converted in units of viscosity.

PT Rating Interpolation Calculation

By pressure and temperature, value between two points can be calculated by linear interpolation.

Calculating Cv Value by using Simple Formula

You can calculate Cv (Flow Coefficient) for the fluid condition entered for the liquid, gas, and steam.

Flow Rate Calculation

Velocity can be calculated from the flow rate. And flow rate can be calculated from velocity.

Unit Conversion

■What is unit conversion?

Unit conversions are calculations which convert units in general physics calculations.

With valves, since fluid flows through the valve, most commonly used unit conversions are those related to fluids.
Therefore, pressure units, temperature units, flow rate units, viscosity units, etc. are covered.

【Pressure Unit Conversion】

With pressure unit conversions, unit conversion between absolute pressure based on absolute vacuum and gauge pressure based on atmospheric pressure tends to be relatively common. The relationship exists between absolute pressure and gauge pressure as below.

Absolute Pressure = Gauge Pressure + Atmospheric Pressure

There are four types of temperatures. Among these, unit conversion is performed between absolute temperature [K] based on absolute zero degrees and the temperature in degrees Celsius [°C] used in everyday life.

Absolute temperature and temperature in degrees Celsius have the following relationship.

Absolute Temperature [K] = Celsius Temperature [°C] + 273.15

【Viscosity Unit Conversion】

Viscosity and kinematic viscosity represents different matters. In addition to unit conversion in viscosity and unit conversion in kinematic viscosity, unit conversion is also performed between viscosity and kinematic viscosity.

Viscosity and kinematic viscosity have the following relationship. Kinematic viscosity is viscosity divided by density.

Kinematic Viscosity = Viscosity / Density

【Flow Rate Unit Conversion】

The concept differs slightly between liquid flow rate unit conversion and gas flow rate unit conversion. With the case in gases, it is slightly more complicated due their volume changes in temperature and pressure. Therefore, for gases, normal flow rate based on atmospheric pressure and temperature of 0°C is often used.
Actual flow rate, which is actual temperature and pressure used, and unit conversions between normal flow rate above are tend to be relatively common.


Liquid and Gas


Liquid and Gas


  • ※ Not applicable to gases.

Flow Rate

  • ※ Due to the relationship between the significant digits, accurate values are not guaranteed. KITZ will not responsible for any problems that may arise as a result of the calculation.
  • ※ Since it is converted as an ideal gas, there may be a difference with the actual fluid.
  • ※ Conversion is based on ideal gas. There may be differences with the actual fluid.

PT Rating Interpolation Calculation

■What is PT Rating Interpolation Calculation?

PT rating is pressure-temperature criteria, which expresses the relationship between fluid temperature and its allowable pressure.
Generally, the higher the temperature, the lower the pressure allowed for use. Also, different materials used will have different values.

PT rating interpolation calculation is approximate linear interpolation calculation from two known pressures and temperatures to calculate the value between two points.
Approximate linear interpolation calculation is based on assumption of linear change between two known pressures and temperatures.

  • ※ This calculation uses linear interpolation to calculate value between the two entered. points.
  • ※ When selecting a valve, please note, it is not only necessary to check PT rating of body and flange material, but also the PT rating of packing, gasket, ball seat, O-ring and etc.

Calculating Cv Value by using Simple Formula

■What is Cv Value?

Cv Value is one of commonly used capacity factors in valves.

Capacity factor of a valve “refers to coefficient which represents the capacity of flow at a given travel.” (From JIS B 0100 Terminology of Valves)
A coefficient which represents sort of performance which allows fluid to flow through the valve under determined conditions, such as valve opening degree and pressure difference (differential pressure) before and after the valve.

A valve with larger Cv value tends to allow more fluid to flow and with larger Cv value allows more fluid to flow at the same differential pressure.

Cv value of a valve depends on the type, size, and shape of the valve.

Cv value for each valve opening degree represents the flow characteristic of the valve.

When controlling flow rate with a valve, by calculating required Cv value with pressure, temperature, flow rate etc of fluid flows through the pipe, a valve with appropriate Cv can be selected.

Cv Value Calculation (Flow Rate, Differential Pressure → Cv)

Flow Rate Calculation (Differential Pressure, Cv → Flow Rate)

Differential Pressure Calculation (Pressure Loss) (Flow Rate, Cv → Differential Pressure)

  • ※ This calculation is a simple calculation that does not include valve data. When selecting a valve, please consider valve’s characteristics.
    Please note, KITZ is not responsible for any problems caused by the calculatin results.
  • ※ Assuming turbulent flow and does not consider viscous effects.
  • ※ As the conversion is based on ideal gas, there may be differences from actual fluid.

Flow Velocity Calculation

■What is velocity calculation?

Flow velocity calculation is one of the fundamental calculations in fluid mechanics.

Velocity is the speed of fluid flowing through the pipe. Velocity can be calculated by dividing the volume flow rate by cross-sectional area.
Below, volumetric flow rate represents the volume of fluid that passes through the pipe in unit time.

Flow Velocity = Volume Flow Rate / Cross-Sectional Area

Also, it is possible to determine the flow velocity from mass flow rate. In that case, the mass flow rate is converted to volumetric flow rate by dividing by density.
Next, velocity is calculated by dividing volumetric flow rate by cross-sectional area.

Volume Flow = Mass Flow / Density

Flow Velocity Calclulation (Flow Rate → Flow Velocity)

Reverse Calclulation (Flow Velocity → Flow Rate)

  • ※ This calculation is a simple calculation that does not include valve data. When selecting a valve, please consider valve’s characteristics.
    Please note, KITZ is not responsible for any problems caused by the calculatin results.
  • ※ As the conversion is based on ideal gas, there may be differences from actual fluid.

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