POWER TRANSMISSION | SPECIFICATION
CHOOSING THE RIGHT VALVES With so many control valves on the market, it’s
Modern process control
valves offer a wide range
of features and benefits
for industries that require
precise control over fluids, steam and
other gases. Here, Damien Moran,
field segment manager, Hygienic
- Pharmaceutical at Bürkert, looks
at some of the basic differentiators
as well as some recent design
developments.
Control valves are used to manage
the flow rate of a liquid or a gas and
in turn control the temperature,
pressure or liquid level within a
process. As such, control valves are
defined by the way in which they
operate to control flow and include
globe valves, angle seat, diaphragm,
quarter-turn, knife and needle valves,
to name a few. In most cases the valve
bodies are made from metal; either
brass, forged steel or, in hygienic
applications, 316 stainless steel.
important to establish the features that will deliver the
most cost-effective design for a particular application.
ESTABLISHING THE
PARAMETERS
Actuators use an on-board system
that measures the position of the valve
with varying degrees of accuracy,
depending on the application. A
contactless, digital encoder can place
the valve in any of a thousand positions,
making it very accurate, while more
rudimentary measurements can be
applied to less sensitive designs.
One of the main areas of debate
when specifying control valves is
determining the required valve size.
Quite often process engineers will
know the pipe diameter that is used
in an application and it is tempting to
take that as the defining characteristic
for the control valve. Of greater
importance are the flow conditions
within the system as these will dictate
the size of the orifice within the control
valve. The pressure either side of the
valve and the expected flow rate are
essential pieces of information when
deciding on the valve design.
IMPROVING EFFICIENCY
Inside the valve body, the actuator
design is predominantly either a
piston or a diaphragm design.
The piston design typically offers a
smaller, more compact valve which is
also lighter and easier to handle
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