Control Valve Sizing and Its Importance

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Control Valve Sizing and Its Importance
From the Perspective of Control Valve Engineering
Consultants Control valves are crucial in
managing the flow, pressure, temperature, or
other variables of the fluid (gas, steam, water,
or chemical) in order to account for load
fluctuations and keep the process variable as
close as possible to the intended set point.
Control valves come in a variety of types, such
as globe, ball, and butterfly. Usually, the
application, prior experience, or plant
preferences will determine the type of control
valve. According to leading control valve
engineering consultants, selecting the right
valve is quite tricky. However, the sizing of the
control valve is trickier. In this blog, we are
going to explain the consideration for control
valve sizing and why it is important. How Are
Control Valves Sized?
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• While sizing a control valve, the general
  approach is to follow the thumb rule. You need
  to size it in such a way that it operates between
  20-80 percent open at the maximum required flow
  rate and wherever possible. Make sure that it is
  not much less than 20 percent open at the
  minimum required flow rate. The goal is to make
  use of as much of the valve's control range as
  you can while still ensuring an acceptable level
  of safety.
• Why Is Sizing a Control Valve Important?
• A control valve that is too small won't be able
  to pass the necessary flow. However, a control
  valve is frequently too big for the application.
  An oversized valve is extremely sensitive to its
  environment.
• Significant variations in flow can result from
  even the tiniest
• adjustments to the valve position. Due to this,
  it is challenging or perhaps impossible for the
  control valve to precisely adjust to the
  necessary flow.
• According to David Moras, an expert control valve
  engineering consultant from SAROM GLOBAL,
  choosing a properly measured and sized control
  valve is extremely crucial for achieving the
  highest degree of control for gas, liquid, or
  multi-phase fluid related
• industries.
• Follow these guidelines for accurate control
  valve selection and sizing
• A valve's flow characteristics are probably off
  if a set of loop tuning
• parameters only works at one end of the control
  range and not the other. Make sure it is
  properly set.
• Use an "equal percentage" control valve when the
  pressure differential across the valve
  diminishes as flow rate increases, and in
  control loops where the process gain drops as
  flow rate increases. A "linear" control valve is
  advised if none of these conditions applies.
• The control valve should be sized to function
  between 20 and 80 per cent open at the maximum
  needed flow and no less than 20 per cent open at
  the minimum needed flow for the best control.
  However,

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• please be aware that this isn't always the case
  for all types of control valves and depends on
  the valve's flow vs. open characteristics.
• properly sized segment balls, full balls, and
  high-performing butterfly valves are typically
  two sizes smaller than the line.
• properly sized globe valves are one size smaller
  than the line.
• Whenever selecting or sizing control valves for
  industrial applications, it is best recommended
  to confer with expert control valve engineering
  consultants. Only professionals are capable of
  accessing and analysing the application to
  select the right choice of valves (including the
  size) that meets the purpose.
• References https//medium.com/_at_saromglobal/contro
  l-valve-sizing-and-its-importance- b9421c4baa50
• Sarom Global
• HQ Australia, supporting EMEA (Europe, Middle
  East, Africa), Asia Pacific, Americas.
• https//www.saromglobal.com/ info_at_saromglobal.com
  61283175089