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A pneumatic 2-hand control device is used with dangerous machinery and requires the simultaneous use of both
hands to trigger and maintain machine operation. Such a device must be located outside the dangerous zone, so
that the operator cannot enter this zone before the machine has come to a complete standstill.
A pneumatic 2-hand control device is composed of 2 parts :
■ 2 manual pushbuttons which require the simultaneous use of both hands.
■ A pneumatic relay.
Types of 2-hand control devices
Synchronous action
An output signal is only generated if both control actuating devices are actuated within 500 ms.
Category 1 (EN ISO 13849) : the system should use well tried components and principles.
Category 3 (EN ISO 13849) : the system must be designed so that a single fault will not cause the loss of the
safety function.
Category 4 (EN ISO 13849): the system must be designed so that an accumulation of faults must not lead to
a loss of the safety function.
Resetting the output signal
The release of a single control device interrupts the output signal, but a reset is only possible once both control
devices have been released.
Requirements
Type
I II III
A B C
Definition (conforming to EN 574 +A1)
Use of both hands (simultaneous actuation)
Relationship between input signals and
output signal
Cessation of the output signal
Prevention of accidental operation
Prevention of defeat
Reinitiation of the output signal
Synchronous actuation
Use of category 1 (EN 954-1)
Use of category 3 (EN 954-1)
Use of category 4 (EN 954-1)
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Conforms to the
Machinery Directive