An added benefit of not using instrument air offshore is the weight savings
realized by eliminating air compressors,
receivers, dryers and other peripheral
equipment. Because an electric actuator
can run from an existing generator, having none of this additional equipment
represents a significant weight savings,
which means a reduction in the support
structure (or jacket) cost.
In the offshore gas production fields of
North West Australia, the most recent
platforms built are unmanned and use an
all-electric actuator configuration,
including the control valve actuators.
In the oil fields of Lake Maracaibo in
Venezuela, electric actuators replaced
the air-powered control valves a decade
ago, eliminating a major availability and
Carbon Concerns: Many industrial
nations are concerned with the carbon
footprint of their industrial facilities. A
carbon footprint relates to the weight of
carbon generated in producing a product
and is a measure of the amount of greenhouse gases produced and the associated
environmental impact. Some manufacturing facilities that see a continuing
demand for their products are feeling
pressure to reduce their carbon footprints
when producing those products.
One major European consumer products manufacturer, for example, has
declared it will double its production over
the coming 10 years, but yet will maintain the same carbon footprint or even
reduce it. A key part of that company’s
strategy is to eliminate use of instrument
air in its facilities. Because air compressors and associated equipment are inefficient for moving power from one point to
another, ceasing use of such compressors
represents a significant energy savings. It
is generally accepted that reducing energy used gives a corresponding reduction
in the carbon footprint.
With the advent of modern electric
control valve actuators, many facilities
have no need for instrument air supplies,
since they were needed only to provide
the motive power to move actuators.
Electric actuator installations are signifi-
cantly more efficient, so major gains can
be made in reducing energy consumption
and thereby the carbon footprint.
A high precision valve being used for chemical
dosing in a water treatment plant.
trol valve positioning can eliminate friction and overshoot effects. This gives
improved control performance when
valves with high seat or packing friction
Smart positioners have made a significant difference in overcoming the inherent resilience of the air power medium in
these circumstances and provide a good
benchmark against which to measure the
latest electric actuators.
Furthermore, the electric control
valve actuator offers another benefit in
this situation. When using pneumatic
control valve actuators in such applications, some basic designs of positioner
may need to be recalibrated at regular
intervals because of “drift” in the position settings. This recalibration is time
consuming, inconvenient and costly.
Because there is no external linkage on
an electric control actuator and all feedback and control is internal to the actuator, there is no drift. This eliminates the
need for routine recalibration.
While traditional spring diaphragm
actuators are preferred in many situations, the list of applications where electric control valve actuators can be a
better choice is growing. The new generation of electric control valve actuators
can provide extremely precise operation, reduce labor-intensive maintenance costs, and often can operate better in bitter cold and other challenging
CHRIS WARNETT is international sales and marketing director, Rotork Process Controls. Reach him