Fluid Flow and Engineering Software

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CONSULTING		   
      
InstruCalc6.1

      Control
      Valve Calculation


      
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      to Introduction


      


      

        

          
            
CONTROL VALVE
            SIZING


            
Three programs are available,
            each for standard and low flow valves:

            Liquid Flow

            Gas Flow

            Two Phase Flow



            Options for each valve calculation are:

            Calculate Valve Size

            Calculate Flow Rate

            Calculate Valve Pressure Drop



            Three cases are provided for each calculation:

            Maximum flow

            Normal flow

            Minimum flow



            Aids for the calculations are -

            Typical valve data tables

            Fluid properties at flowing conditions

            A program to calculate the valve pressure drop available in the
            piping system


            
After using the above for normal
            flow to determine the valve size, scroll bars will change the
            flow, recalculate the data and determine the maximum and minimum
            flows that the piping system will allow.


            
The programs have a data base
            of typical valves so that different valve data can be entered
            into the calculation in order to make the best selection. Try
            several and calculate until a valve style and size is selected
            which has the rangeability and does not have cavitation or noise
            problems. When a final selection is made the exact manufacturers'
            data can be entered for a final calculation.


            
Finally, for liquid valves in
            long piping systems, take the option for the minimum closing
            time, this is the water hammer program to determine if a special
            closing time is required to avoid water hammer.


            
Sizing Philosophy


            
Each manufacturer has its own
            formula for determining the valve size, the valve noise and the
            cavitation characteristics. This program uses the ISA sizing
            formulas, it uses the Masoneilan noise prediction method and
            incipient cavitation technique. The object of the program is
            to determine the valve size, the cavitation, flashing and noise
            problems and prepare a data sheet suitable for bid purposes.
            Some manufacturers may differ from these conclusions, usually
            the variations are minor and do not change the size and style.
            Occasionally the noise and cavitation characteristics will differ
            so that engineering judgment may be called for. The failure of
            a valve because of cavitation erosion can be extremely expensive.
            Sometimes a change in body style, or hardened trim is sufficient
            to eliminate the problem,


            
The typical valve data files
            are in ASCII format, three options are provided. They are Standard
            Valves, Low Flow Valves and a file for User Valves. They can
            be modified from within the program. The Standard file is based
            on Masoneilan data. The Low Flow file is based on Research Control
            Valves data. If another manufacturer is preferred edit the User
            valve file as required. If the manufacturer does not use the
            incipient cavitation factor (Kc) then leave the box empty. ISA
            S75 shows data for a typical file.


            
References

            Control Valve Sizing Equations ANSI/ISA S75.01.01-2002

            Masoneilan Noise Control Manual

            ISA Handbook of Control Valves J. W. Hutchison


            
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            to Introduction
          

        

      


      

        

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