This procedure enables you to enter various values for calculating a control valve. First, you define a CV calculation method and a flow coefficient standard (US or Europe) of CV sizing, then you select a noise calculation method and a CV body type. Next, you enter values, perform the calculation, and view the results.
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By default, Smart Instrumentation updates tag values from the current unit of measure to their value in a new unit of measure that you set. If on the Options menu you clear Automatic Unit Conversion, the software changes the unit of measure without recalculating the values. Therefore, to protect the integrity of your values, on the Options menu, select Automatic Unit Conversion.
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To highlight the fields that are required for a calculation, on the Options menu, select Highlight Process Data.
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Open a control valve calculation item.
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If you defined multiple process cases, from the Case list, select the case that you want to calculate.
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Make sure that you enter process data in all the fields in the data sheet that are required for calculation.
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Select
to save the values.
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Select Actions > Calculate
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Calculation is disabled for N/A or other fluid state.
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In the Control Valve Calculation dialog, from the Calculation method list, select the required calculation method, that is, ISA or IEC.
The IEC standard is 60534- 2-1 (1998)
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From the Flow coefficient list, select the required flow coefficient standard of CV sizing (Cv or Kv).
Kv is a European standard flow coefficient available for an IEC CV calculation method.
Kv = Cv * 0.865
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Based on the value that you selected from the Fluid state list on the process data sheet, do one of the following:
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If you set Liquid or Water, select Masoneilan or IEC from the Noise calculation method list.
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If you set Gas/Vapor or Steam, select ISA or IEC from the Noise calculation method list.
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Enter hydrodynamic noise data as necessary.
This option is available only if under State you selected Liquid or Water, and under Noise Calculation Method you selected IEC.
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From the Body type list, select the required body type.
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Enter the required critical flow factor values (Fl, Cf) at minimum, normal, and maximum control valve coefficients.
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To define the required pressure drop ratio factor values (Xt) at minimum, normal, and maximum control valve coefficients, do one of the following:
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To calculate the values automatically, as a function of critical flow, select Calculate pressure drop ratio factor.
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Type the required values in the @Minimum, @Normal, and @Maximum fields.
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Type the Valve style modifier (Fd) value.
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To set the Relative capacity value, do one of the following:
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Accept the value that Smart Instrumentation calculates based on the calculation method and on the standard that you selected from the Flow coefficient list.
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Type the value that you require.
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Type the required Number of flow passages.
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Enter the appropriate Valve size and select its unit of measure.
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To set the Internal pipe diameter at valve outlet, do one of the following under Internal pipe diameter at valve outlet:
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Manually type the value required.
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Copy the internal pipe diameter value from either the Upstream line or Downstream line by selecting the correlating radio button and selecting Copy from.
Copy from is disabled when the same line is used for upstream and downstream. The user should
insert the pressure drop data and the software will calculate the downstream pressure.
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Select Calculate to carry out and display the calculation results.
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Examine the figures for results that may have to be re-calculated.
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To recalculate the control valve parameters, enter the new data and select the Calculate command button.
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Select Close to return to the calculation data sheet.
You can calculate a control valve and the relevant parameters even if the pipe wall
thickness is not defined. In this case, Noise is not calculated and a line of text in Notes section of the calculation sheet informs
you that Noise will not be calculated because Pipe wall thickness is not defined.