Understanding Presence Sensing Devices
All types of press brakes put their operator at risk. The job is inherently dangerous, so safety measures are absolutely essential. The OSHA (Occupational Safety and Health Administration) approves the use of presence sensing devices on a case by case basis as long as they meet certain criteria as defined on the OSHA website. This article discusses some advantages and accompanying regulations of presence sensing devises (also known as close-proximity point-of-operation AOPDs or active optoelectronic protective devices).
What are the Advantages of Presence Sensing Devices?
Presence sensing devices typically allow the operator to get closer to the point of operation than other methods without any obstacles or hindrance. There are no straps, leashes, or physical barriers blocking the way as long as the zone in question is protected by the PSD. Therefore, there are no limitations to restrict the maneuvering and bending of sheet metal. Operators generally tend to prefer PSDs.
All three types of presence sensing devices (infrared “light curtain”, laser beam, and camera based sensors) are cost-effective, typically more so than the majority of other safeguards, and pose very little risk of slowing down the production process. These systems are designed to stop the ram immediately if the safety zone is breached by anything. Though relatively affordable, they’re quit effective, and have gained prominence in facilities around the world as a result.
Presence Sensing Devices Are Commonly Used in Combination with Foot Pedals
“Dual-channel” setups increase safeguarding effectiveness even if a single component of multipronged safety equipment or only one signal fails. Having both safeguards increases operator reaction time in the event of an incident. For example, if one of the operator’s fingers were to get pitched or caught in a part of unit that is not safeguarded by a laser beam, camera, or light curtain, they would still be able to disable the machine the instant they felt pain. If used, every foot pedal must be covered to prevent accidental engagement or disengagement.
What if the Dies Never Require Hands in Die Operation?
As defined by the OSHA standard:
“…In the absence of applicable specific standards, [the guarding device] shall be so designed and constructed as to prevent the operator from having any part of his body in the danger zone during the operating cycle.”
Presumably, this means that if the operator is not required to work in close proximately to the point of operation, even if they can be proven to be kept at a relative safe distance at all times during operation that safeguarding is indeed needed surrounding the point of contact. Also according to the defined standard, “Under all circumstances, press brake operators are exposed to point of operation hazards, therefore, safeguarding the operator is a requirement of OSHA and the ANSI.” Yet, two-hand safeguard systems alone count as adequate safeguarding.
Operators can remain essentially unprotected from possible debris and still adhere to current regulations. An operator in 2005 was killed from an ejected piece of steel, which prompted OSHA and other similar entities to tighten regulations. Ironically, a physical barrier is still not necessarily required. OSHA specifically has, however, imposed a six-inch regulatory limit from the closest edge of the dies to the operator if the metal is hand-held.
Presence Sensing Device Restrictions
PSDs cannot be used with press brake systems using full revolution clutches. Physical barriers must be in place to protect all areas that are not protected by the PSD. Deliberate disengagement of a PSD, or “Muting”, is permitted only for actions that include parts ejection, circuit checking, and feeding. Otherwise tampering with PSD protection may result in failure to pass regulatory inspections.
For More Information on Press Brake Safety Requirements
To learn about the regulations and requirements of each device, visit the OSHA website.