Combining valves and actuators
to create energy-efficient control
devices
Automated valves play a pivotal role in the field of process technology: they regulate flow
rates, prevent unwanted product flow and help to clear supply lines. Regardless of the valve
design – whether butterfly valves, standard valves, ball valves or gate valves – pneumatic
actuators are frequently used in the field of automation for several compelling reasons: this
kind of actuator is characterised by its high levels of fatigue resistance, low maintenance
requirements and cost-effective operation, in addition to being an excellent choice for applications in hazardous areas. In this context, the fundamental challenge is to ensure optimal
interplay between the valve and the actuator, while paying particular attention to the clientspecific application conditions. The following article shows that, with increasingly powerful
systems and increasingly complex requirements, coordinating these two components as
accurately as possible is indeed worth the effort. The article considers different approaches
with the aim of guaranteeing an environmentally sound, energy-efficient and therefore economical control unit.
PETRA STRICKER, DIANA VÖLKEL
THE 1+1=1 PRINCIPLE
An automated valve from a single source offers a range of tangible benefits for the user. By coordinating
the actuator and valve with each other, the device can
be tailored precisely to the field of application. The advantages of this approach go well beyond the aspect
of torque alignment. Indeed, elements such as operational performance relating to rapid and frequent switching cycles, continuous operation performance, life
cycle cost data, operating limits for temperature and
ambient conditions and many other aspects can be
more precisely planned when producing actuators
from a single source. Due to the rapid speed of progress in the field of automation and the associated
functional complexities, the requirements for control
valves are becoming more and more extensive. The
emphasis is on ensuring process reliability and functionality. At the same time, however, European directives,
Figure 1: Direct installation
of actuator and pneumatic
accessory on a butterfly
valve ensures a superior
force-fit connection between
the components.
service life with lower levels of wear and increased efficiency.
*1
*2
*1 = Effective torque in Nm; *2= Angle of rotation in º
Figure 2: Ideally suited to the automation of butterfly
valves: the Scotch Yoke actuator with highest torque at
the end positions. In this case, the torque progression is
for a double-acting quarter-turn drive.
guidelines, standards and specifications all have an impact on the requisite design of components. Customers
can be provided with all the necessary certificates and
approvals from a singe source, along with the full range of
documentation and related services. Given these complexities, it makes sense to consider the valve and actuator
as one complete unit, as operational reliability and costeffectiveness can only be guaranteed if the control device
as a whole is both functional and efficient in its design.
Figure 1 shows how the direct installation of actuator and pneumatic accessory (in this case a
switch box from the SBU range) on the butterfly valve ensures a superior form- and force-fit connection between the components. This ensures a longer
1: THE BUTTERFLY VALVE
The next issue to consider is the interplay between the components by means of a pneumatically automated centric butterfly valve. Centric
valves achieve their sealing properties thanks
to the oversized butterfly disc pressed into the
liner. This oversize is defined through precise
machining in order to ensure that it provides a
secure seal against the operating pressure in
the system. This provides considerable advantages: torque is optimised, while wear is minimised and the energy required for valve automation is significantly reduced. In many cases,
a smaller and lighter actuator can be used for
automation. In combination, these factors help
to reduce investment costs as well as long-term
operating expenses.
+1: THE ACTUATOR
Expertise gained from the valve manufacturing process can also be applied to the
field of actuator development, as the torque
progression of the actuators can be adapted to meet the requirements of the valve.
Which functional principle is best suited to
the automation of butterfly valves with a 90º
angular stroke? Compared to the rack and pinion principle, the design of the Scotch Yoke actuator offers the benefit of much higher torque not
only at the end positions (figure 2) – with the
same inner cylinder diameter – but also at the
middle position, as the space is put to better use
(figure 3). The air consumption per stroke is also
significantly lower with the same torque rating.
Figure 3: The lever-arm geometry of the Scotch Yoke actuator requires less construction space for
the same torque, and therefore a lower filling volume than actuators based on the rack and pinion
principle.
with an extensive number of automated valves
and high switching frequencies. Depending on the
overall quality and the production equipment for
the supply air, considerable savings can be made.
Example calculations carried out based on larger
systems with 40 to 60 automated valves indicate possible savings of several thousand euros
per year, depending on the switching frequency.
SUMMARY
Essentially, a unit as a whole (figure 4) can be considered energy efficient if the valve is designed
in a torque-optimised manner and the construction of the actuator is such that its air consumption is as low as possible. Saving energy means
operating the systems at optimal output with the
lowest possible levels of energy consumption.
The energy-efficient operation of pneumatic
actuators in industrial systems will always be
possible if the following two conditions are met:
Figure 4: Whether single or double-acting, the EB actuator
series is attuned to the torque requirements of the butterfly
valves.
What is more, the state-of-the-art coating applied to the aluminium actuator housing helps to improve performance,
while also contributing to overall energy efficiency. Additionally, the polymers found in the special coating layers
continuously self-lubricate, thereby preventing any stickslip effect. The friction coefficients (static and dynamic) are
reduced, which in turn increases the actuators efficiency.
= 1: THE CONTROL DEVICE,
THE AUTOMATED VALVE
The automated valve, or control device, proves to be
particularly efficient when the drive torque moves in
close correlation with the torque of the valve (taking
into account a safety margin). Intelligent accessories including delay elements, compressed-air return
systems, parallel control units, end-position damping
systems and pressure-boosting systems provide end
users with the ideal solution for their applications.
It is worth viewing the individual components as a single unit, as the combination ultimately determines
the device‘s overall efficiency. Air consumption plays
a considerable role, particularly in larger systems
•
Actuators and valves are optimally coordinated to one another and
form a “harmonious” automatic valve
•
The pneumatic actuator is designed
such that low air consumption is guaranteed
AUTHORS
PETRA STRICKER
E.A. Antriebstechnologie &
Services GmbH
58135 Hagen, Germany
Tel.: +49 (0)2331 904 151
[email protected]
DIANA VÖLKEL
EBRO ARMATUREN
Gebr. Bröer GmbH
58135 Hagen, Germany
Tel.: +49 (0)2331 904 202
[email protected]