Hydraulic presses can be quite large and powerful pieces of equipment. As time has passed, it's become more imperative to protect against the potential hazards associated with them. ANSI and OSHA have minimal requirements for machine safety. Two of the most valuable hydraulic press components that can help you meet those safety requirements are safety light curtains and safety switches.
Often, these components are misused or the wrong one is selected for the application, causing numerous safety issues. Ensure your components are being used correctly and avoid making these mistakes when using light curtains and safety switches...
Misusing Light Curtains for Your Application
Light curtains are made of two light bars, an emitter and a receiver which can both move. They can help protect workers from hazardous situations such as a press in motion. When used with a hydraulic press, the light curtains are meant to be set at a safe distance between the press and the operators. Too often safety light curtains are being set too close to the press, or the same brand and model of light curtains are being used for multiple applications at a given facility. It’s important to verify your safety light curtains are placed far enough away from the press, so the machine has time to stop before a person can reasonably reach the press. There should be guidelines set at your facility for beam resolution vs distance from work being performed to uphold your safety standards.
Also, an issue with light curtains is selecting the right one for a customer’s applications. The safety curtains’ light bars emit infrared light beams across to the receiver bar, these light beams are separated by a set distance. Selecting a light curtain with too large of a beam separation can create hazardous situations. For example, if your light curtain and press are inches apart, and the light beams are separated by 2 inches, it is very possible a person could stick their hand through the light beams without triggering a shut off. In doing so, they’re risking an injury.
If you’re unable to place the light beams at a safe distance from the press, you need to ensure the beam separation is small enough to properly trigger a shut off if a person or object passes through beams. Ensure you’re selecting the right light curtain for your hydraulic presses set up.
Not Enough Safety Switches
Safety switches are often used to protect people from entering a dangerous space. A safety switch can sense when a gate is open or closed. To open said gate, the solenoid which acts as an electromagnet inside of the switch needs to be energized. As a result, safety switches are often involved with a safety relay. If the safety switch or safety relay were to notice faulty wiring or a problem with the interlocked/monitors contacts, it would disable the safety relay output and default back to a “safe condition” to stabilize the switch.
Certain applications use regular limit switches where there should be a safety switch. Limit switches are great for knowing the machine's position and protecting the machine from itself, but when it comes to human life and safety, limit switches may not provide full protection.
Safety switches and limit switches operate similarly to one another. Too often limit switches can be toggled or bumped up against and moved which compromises their abilities to properly shut off the motion of a press. Safety switches have precautions set up to prevent such a risk and for extra protection, they can be paired or keyed. Some safety switches have RFID sensors in them so the machine can only be activated for its programmed key. It helps prevent operators and maintenance from defeating the switches and walking into a dangerous situation.
Safety switches can be more expensive than a typical limit switch and require more than two wires to set up/use, but choosing to use a limit switch over a safety switch can create potentially hazardous work scenarios. Implementing safety switches wherever possible can help you better protect your workers and your business from unnecessary risk.
