Manual override

Easy maintenance with Bernard Controls manual override technology

Depending on the markets and types of facilities, the features of emergency manual control, key functions of the actuator, can be very different. However, several features have a prime significance.

Manual override specifications:

Manual override with electrical priority is required in most of the technical specifications. However, the following two principles must be adhered to:

  • it must be possible to operate the handwheel at any time
  • the number of turns on the handwheel must not be too high.


Example 1
:
On a pressurized steam circuit, the valve closes on torque. When the torque is high, the use of a dog coupling is not safe enough as the force to be applied to the clutch lever for switching to manual mode is high.

Example 2: Depending on the technology used, the number of turns on the handwheel can vary from 30 to more than 500 turns, in order to drive a DN500 quarter-turn valve with a torque of approximately 2500 Nm. Thus, the stacking of reduction gears can inhibit the safety function of the manual control.

In conclusion, there is not one solution for all the applications but different techniques adapted to the real needs.

Correct sized handwheel gearing

Quarter-Turn Multi-Turn

Torque (Nm)

Number of turns

Torque

Rate

60 to 100

21

 < 60 Mm

 1/1

100 to 150

9

 < 300 Mm

 1/2

150 to 300

11

 > 300 Mm

 1/*

300 to 800

8

   

500 to 1000

14

 

 

≥1000** (multi-turn + gearbox)

*

   

* according to torque
** for torque values, please consult us

Safety

QUARTER-TURN

Non rotating handwheel, with electrical priority for high torque values

MULTI-TURN
CONINUOUS MODULATING

Non rotating handwheel, with electrical priority and without declutch*

* Except for ST6