SA's own control-valve sizing program

August 2001 Valves, Actuators & Pump Control

Mitech has recently released what it claims to be the first computerised control valve sizing program to be written in South Africa. Windows-based, this program runs on any PC operating in a Windows environment, including 3.11, 95 and NT. Although best operating speeds are experienced when using a Pentium processor, the program does run on a 386.

The user is prompted, in stages, to enter information about the conditions under which the valve will operate. When performing fluid selection 'water' appears as a default in the box, being the most common of all fluids being controlled - but opening the pull down box gives one the choice of 40 pre-programmed fluids from which to choose - including Castle for those who want a South African flavour! The 'New Fluid' option enables the user to enter information about any fluid not on the list. The more information available the more comprehensive the sizing that the program will be able to carry out.

Temperature can be entered in degrees Celsius, Kelvin, Fahrenheit or Rankine - whichever is most convenient. The choice of flow rates is even greater since both mass and volume flow rates are catered for. The most common are 'm3/h' and 'tons/h' - but for those who work more comfortably with 'litres/sec' the choice is available.

A useful feature is a check box called 'Convert units'. When checked the selection of a new unit - whether for pressure, temperature, or flow - causes the entered values to be converted from the old units to the new ones. If unchecked the values remain the same.

Depending on the values of inlet pressure and temperature entered the state of the fluid is displayed as either liquid or gas. This is designed to help prevent some of the more serious problems experienced with computer sizing of control valves. In addition if the computer is able to identify a problem moving onto the next page is prevented (for example if water has been selected but the temperature is higher than the saturated temperature for the inlet pressure).

Once the correct valve type and size has been selected the results can be printed. All input data and calculated results are printed out along with a graph showing the control position at maximum, normal and minimum conditions. Exiting at any point in the program saves the data for future retrieval. Records can be exported and imported for transfer between machines either on disk or by e-mail. When leaving the valve-sizing program the user is returned to the index page where actuators can be chosen. This can follow on from the selection of a rotary control valve or be used independently.

The actuator-sizing program caters for Mitech's rotary and linear pneumatic actuators. In both cases the correct actuator model is selected from the complete range based on certain input information. The results can be printed for reference or quotation purposes.

Mitech is making this program available to all existing and potential customers free of charge, but strongly recommends that all serious users attend the intermediate control valve training course that it is being run. This course is a follow up for the basic control valve course the company has been running for the last five years around the country. Over 500 people including artisans, foremen, technicians, and engineers have attended these courses, coming from instrumentation, mechanical, electrical, and process backgrounds.

Mitech

(011) 462 2160

[email protected]

www.mitech.co.za

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Valves, Actuators & Pump Control

SA's own control-valve sizing program

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