Axel’s tips - What is the point of two-hand control?

Often two-hand control is primarily understood as a means of starting a hazardous process, ensuring that the operator cannot reach into the hazard zone with either hand. But that is only one half of the story. Looking at the definition in EN ISO 13851 you will find two additional points worth considering:

1. “[Two-hand control is a] device which requires simultaneous actuation by the use of both hands in order to initiate and to maintain hazardous machine functions, thus providing a protective measure only for the person who actuates it”.
    
2. The buttons do not just start the hazardous function, but must be held down, until the hazard is gone. In a long-stroke application this would mean that the operator must hold both buttons down until the stroke is finished. And this also means, that the movement must stop as quickly as possible, if the operator lets go of one of the buttons. Two-hand control thus is a control function forcing the operator to stay in a defined location outside the hazard zone as long as the hazard is present.
    
3. But it protects only one operator. Others are not protected. Therefore, other safety measures may have to be taken to protect others around the machine. This requires at least the following (compare EN ISO 12100 section 6.2.11.8):

• The entire accessible hazard-zone must be visible from the operator’s workstation. Otherwise he might inadvertently endanger a person entering the hazard zone.
• The access opening(s) to the hazard zone should be as small as possible, so nobody can intentionally reach into the hazard zone or accidentally stumble and fall in. Ideally, the access opening would be just large enough to perform the operation, such as inserting and removing parts. To reduce the access opening one may have to install stationary and/or movable guards.

EN ISO 13851, which addresses two-hand operation, is one of the three most important basic safety standards for manual workstations that has recently been revised.

In our White Paper, we give tips on what also should be taken into account in these work environments.
Here you download our White Paper