The actuators provide fastening holes of different dimension to facilitate
mounting on different types of valves, see details in Figure 20 on page 34 and
Figure 21 on page 35.
When the actuator and the valve do not have a natural match, it is necessary to
use an adaptor. There are various adaptors available, but the two most common
ones are the square reducer and the flange + stem adapter. When buying
actuator and valves together from Eltorque, this is handled by our project
personnel. If you order just the actuator take care to verify the critical
dimensions and whether the valve has parallel or standard configuration. Square
reducers might be necessary. Always use two pieces with QT250. The QT800
only has room for one. The type of reducer to be used depends on the valve type,
please contact your Eltorque representative or Eltorque support for further
details.
Figure 18: QT250 and QT800 Settings for closed position.
The setting for closed position can be changed by using E3C, see Eltorque E3C
Manual.
The actuator must have sufficient torque to operate the valve in all situations
with an acceptable safety margin. Valve type, temperature, operating pressure,
medium density and viscosity and the medium’s effect on the valve friction are
among the variables that need to be evaluated. A change in any of these
variables may change the required operating torque. Preferable a torque table
with all parameters should be used, but for an electrical actuator, the output
torque is constant, reducing the considerations to be made. Using the break to
open (BTO) value usually gives a correctly sized actuator. The break to open
torque is defined as the torque required to move the valve out of the seat.
Be aware that the MAST of the valve needs to be verified to prevent damage to
the stem. Eltorque can assist with the necessary experience in selecting the
correct actuator size for the valve.
For the QT250 and QT800, the closing time is configurable within a predesigned
interval. The opening and closing profiles are shown in Table 5: System
performance parameters for QT250 and QT800 actuators on page 19.
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