Are Your Press Controls Safe?April 30, 2020
1. We use light curtains in our pressroom. My press operators are safe, right?
Light curtains by themselves do not make the press safe to operate. In fact, if not used properly, they can give operators a false sense of security. Consider these issues when using light curtains:
- Safe distance. OSHA, ANSI and CSA publish a safety-distance formula. When using the formula correctly, metal formers will mount the light curtains at a distance far enough from the pinch point so that when an object triggers the curtain, the press will stop before someone can become pinched, or worse. Mounting the light curtains closer than the safe distance possibly can prevent the press from reacting quickly enough to avoid injury.
- Safe distance changes. Over time, the brake on a press will wear and the stopping time will increase, causing the required safety distance to increase.
- Unguarded areas. Along with light curtains, stampers may need to install additional hard guarding around a press, to prevent the entry of hands or fingers into the point of operation by reaching through, over, under or around the light curtains.
- Shops operating older light curtains should verify with the manufacturer that they meet current safety standards.
- Existing press controls. When using light curtains as a primary safety device, the press controls must be “control reliable” and include a brake monitor.
2. We installed a brake monitor. Does the press now comply with standards?
Not necessarily. Brake monitors basically are reporting devices that will not control the stopping of a press. They will provide the amount of time it takes for the ram to stop when the clutch is turned off, and prevent another stroke when exceeding the programmed maximum stopping time. To make a press compliant and safe, also consider and address the clutch/brake controls and press guarding.
3. How can we calculate safety distance?
According to OSHA 1910.217(c)(3)(vii)(c), calculate safety distance (Ds) by the formula:
Ds (in.) = 63 in./sec. x Ts, where:
63 in./sec = hand-speed constant; Ts = stopping time of the press (measured at approximately 90-deg. crankshaft rotation position (sec.)
4. One of our press controls still employs the original relay-logic clutch/brake circuit. Does it comply with standards?