Rethinking machine safety risk
The design phase of a project allows companies to reduce potential machine safety risk before it has a chance to manifest itself as a hazard and danger to workers.
One of the most important areas to reduce safety risk in machines comes at the design phase of the project.
“Safety built in at the beginning works best. As an OEM (original equipment manufacturer) starting off with the design process, you are dealing with safety and risk at the beginning of the process,” said Chris Gerges, president and chief executive at Safe-T Sense Machine Safety during a session entitled “Rethink your machine safety risk strategy: Understanding the validation process” at the Siemens Automation Summit 2019 in Aurora, Colo. “The most reliable risk reduction measures come at the design of the machine. If you have a pinch point you can design out the pinch point. In many cases, if you don’t need 100 newtons of force to pick it up and you only need 30 or 40 newtons you can design in only that amount.”
The idea of validation wraps up multiple elements of safe operations, including factors such as the performance of preventive technologies and techniques, documentation and the likelihood that safety features can be bypassed. It also looks at residual risks that remain after all steps have been taken and employees have been trained to avoid accidents.
Also, as a part of validation, a manufacturer wants to assemble a diverse team. That is because the more diverse the team is, the more it is they will see all the potential risks.
“As an OEM you are dealing with validation when the machine is coming off the manufacturing floor,” Gerges said. “Machine building ensures you are following risk reduction measures accordingly. You should follow the guidelines you have implemented with the risk assessment.
“When you are done with the machine build up, prior to shipping the machine out to your customer you will go out and do a validation before shipping to make sure it applies to the safety standards.
That is part of validation for the OEM, but what about the user?
“On the user side, you have to deal with validation you will go out and do a validation with the machine builder. You will be going over the risk reduction measures.”
Gerges talked about the six hazards in the control hierarchy from most to least effective:
- Eliminate the hazard
- Substitute the hazard with a safer alternative
- Isolate the hazard from anyone who could be harmed
- Use engineering controls to reduce the risk
- Use administrative controls to reduce the risk
- Use personal protective equipment (PPE) and wear gloves and goggles when using the machine.
Validation and verification are crucial safety factors that constantly need to be reviewed to make sure equipment remains safe to continue making product and allow workers a safe environment.
The following are validation elements to look at for various safety elements:
Validation of fixed guards
- The actual reaching over under or through it
- What is the gap opening
- What is the purpose of the fences? Ejection, prevention of reach
- Tools necessary for removal
- You need to look at the reaching distance. Can I actually reach over a fence?
Validation of light curtains
- Mounting off the ground surface
- Reaching over or around
- Minimum distance
- Muting and blanking
- Reflective surfaces
- Short circuit protection
Validation of laser scanners
- Very convenient as you can set them up and detect an object
- You have to take into account the environment
- Mounting off the floor
- Detection zone
- Password protection, change the password from the default
- Minimum distance calculation, doesn’t prevent you from reaching the device or the hazard you have to take this into consideration
- Reaching over or around
- Short circuit detection.
Validation for e-stops
- Color of mushroom button
- Color of the background
- Latching in the pressed position
- Easy to be reached.
Validation for guard interlocks
- Does the interlock acted as an end stop for the guard
- Are the actuator screws fixed to the mounting
- Minimum distance calculation
- Short circuit protection.