What is interlock blocking and how does it help prevent an unexpected start-up?
Any time an individual is performing a task inside the perimeter of a safeguarded space, known as a whole-body access application, there is a risk that the machine could be inadvertently reset and restarted while they are still inside.
This risk is commonly referred to as unexpected start-up and can be incredibly dangerous, points out safety equipment designer and manufacturer Fortress. “Interlock blocking is a simple, yet effective, way of safeguarding against unexpected start-up by providing individual control to each person who needs to enter the area by preventing the interlock from being able to close until all individuals have safely exited the space.
“By giving control over when the machine can be reset to each individual, this can provide better protection and peace of mind than relying on the reset location having a good view of the safeguarded space and can be a much more cost-effective method than using presence sensing devices, which can be difficult to implement in large or complex areas.”
Interlock blocking can be achieved in a number of ways, according to Fortress:
Physically preventing the actuator of a Type 2 interlock entering the head – attaching padlocks to the tongue / actuator; attaching padlocks to block the head
Physically preventing the door from closing – using a mechanical interlock blocking device
Preventing the interlock from locking – using a safety key built into the interlock, which will not allow the interlock to lock or send a signal allowing reset until it is returned.
But what if I’m not using hard guarding? “When light curtains are used in place of physical guards, the same risk of unexpected start-up exists,” states Fortress. “In this case, it is possible to use a similar method to give individual control and prevent unexpected start-up.”
Solutions recommended include:
Physically block the light curtain –using a mechanical blocking device
Preventing the light curtain from being reset – using a safety key module linked to the light curtain.
Fortress offers a wide range of interlock blocking options, including safety keys and/or padlock points available across its interlock ranges, as well as retrofittable interlock blocking devices that can be readily fitted, “without wiring, to hinged or sliding doors or light curtains, regardless of the interlock / light curtain currently being used”.