Most industrial equipment requires human interaction to function. Workers must be protected from dangerous interactions with machines. Calculating the minimum safe mounting distance is vital to ensure worker safety. In addition, excessive mounting distances use up valuable floor space and can increase the time required to service machinery, which in turn reduces throughput. Today we will be discussing safe mounting distance formulas as well as the resulting difference between a safety rated PLC solution and safety rated relay solution.
Calculating Safety Distance of Safety Light Curtains
Calculating a Safe Distance between to position a Light Curtain from a potential hazard.
When safeguarding your machinery, it is not enough to simply install a light curtain s and assume that the machine is now safe. This post explains how to calculate safety distance for light curtains. Then, once installed, use a stop time measurement STM device to calculate how quickly the machine stops, and use this value to determine the minimum safety distance required. Taking the time to calculate safety distances upfront not only ensures compliance with global safety regulations, but also helps prevent long term costs of injury and machine downtime. For example, a mechanical power press cannot immediately come to a complete stop. Rather, it takes time for the machine to respond to the safeguarding device and all interfaced components before achieving a complete stop. Additionally, some machines may have a coast down time due to a rapid process that cannot be stopped quickly without damaging the machine or products.
How to Calculate Safe Distances
Calculating Safety Distance When installing safety light curtains, a minimum safe distance that the light curtain can be mounted from the point of hazard must be calculated. The distance between the hazard and the light curtain must be such that the time it takes the operator to reach the hazard with respect to approach speeds of parts of the human body is greater than the stopping time of the machine. In the United States there are two formulas that are used to properly calculate the safety distance. The first, the OSHA formula, is the minimum requirement for the calculation of the safety distance. The second formula, the one recommended by United Machine Corporation, is the ANSI formula, which incorporates additional factors to be considered when calculating the safety distance.
The effective sensing field of the device shall be located at a distance from the nearest recognized hazards such that the operator or others cannot reach the hazard with a hand or other body part before cessation of motion during the hazardous portion of the machine cycle. The point at which a device responds to an intrusion may vary. The devices should be located or adjusted such that the device always responds to the intrusion at or prior to the safety distance.