for high temperature or very fast
The benefits of the integral
output drive include the fact no
stem nuts exist to wear out or
fail, less mounting adapters are
required, and the system is
closed, which eliminates the
ingress of dust and dirt, etc.
When converting a rotary
actuator to linear output, the
force measurement at the final
output element is measured as
thrust. The actuator manufacturer can provide the conversion
information so that torque
switches can be properly set.
electric actuators also are available with integral output drives
Figure 2. For integral output
drives, no stem nuts exist to
wear out or fail, less mounting
adapters are required, and the
system is closed.
that will do this calculation internally
with settings done in thrust values.
The torque setting values when a
threaded stem and stem nut are used
are typically out of the hands of the
actuator manufacturer. Values such as
stem factor are typically the valve manufacturer’s responsibility. With this
knowledge in hand, converting to a
rotary torque value becomes a simple
These are just two of the most common and cost-effective methods to convert rotary actuators to linear output.
Applications with other types of output
drives such as ball screws will benefit
from further research by end users. VM
PAUL SOUZA is quality assurance manager for
AUMA Actuators, Inc. ( www.auma-usa.com),
Canonsburg, PA. Reach him at