Machine guarding is essential for workplace safety as it protects employees from potential hazards such as moving parts, sharp edges, and points of operation. Correctly determining the placement distance of machine guarding away from the hazard is critical to their effectiveness. Improper placement can render guards ineffective or inconvenient, leading to safety violations and increased risk of injury.

The placement distance of machine guarding directly impacts its ability to protect workers while maintaining operational efficiency, said Ray Niemeyer, Vice President of Sales at SpaceGuard Products. The company is a member of the Protective Guarding Manufacturers Association (ProGMA).

“Guarding placed too close to the hazard may still allow accidental contact. Machine guarding placed too far away can impede productivity or fail to provide the intended protection,” he explained.

As a general rule of thumb when using steel mesh panels, continued Niemeyer, the smaller the openings the closer the panels can be to the hazard.

“If you’re guarding a robotic palletizer handling cases, you can go with a larger mesh opening because the cases aren’t going to pass through the openings. Conversely, if you’re guarding a robotic drilling or cutting machine that’s generating metal shavings, those could easily pass through larger openings. In that case you’d want very small openings or solid panels,” he said.

Refer to Standards for Guidance on Machine Guarding Placement

Multiple standards include guidance on appropriate spacing of machine guarding around a hazard. They include:

• ANSI B11.19: Performance Requirements for Risk Reduction Measures: Safeguarding and Other Means of Reducing Risk. This standard provides performance requirements for the design, construction, installation, operation, and maintenance of the risk reduction measures applied to machines, including guarding.
• ANSI/RIA R15.06: American National Standard for Industrial Robots and Robot Systems – Safety Requirements. This document shares guidelines for the manufacture and integration of industrial robots and robot systems. It emphasizes their safe use, the importance of conducting risk assessments, and how to improve personnel safety.
• ISO 13857:2019 – Safety of Machinery – Safety Distances to Prevent Hazard Zones Being Reached by Upper and Lower Limbs. This standard details values for safety distances in both industrial and non-industrial environments to prevent machinery hazard zones from being reached. It also outlines the appropriate safety distances for protective structures.
• OSHA 1910.212 – Machinery and Machine Guarding. This outlines requirements for machine guards to protect operators and other employees.

Reach Envelope and Safe Distance Calculation

The reach envelope is the area within which a person can extend their body or limbs. Use safe distance formulas, such as those provided by ANSI B11.19, to calculate the appropriate guard distance. For example, a common formula is: D = K × (T + C)

Where:

• D is the safe distance (in inches or millimeters).
• K is a constant representing hand speed (typically 63 inches/second or 1,600 mm/second).
• T is the response time of the safeguarding device (in seconds).
• C is the additional distance based on the depth of penetration of the hazard (in inches or millimeters).

Step-by-Step Process for Determining Machine Guarding Placement

It’s important to conduct a risk assessment to help with the determination of machine guarding placement, added Niemeyer. Additionally, he advised the following process for determining where to position the guards.

1. Assess the Machine and Hazards. Identify all potential hazards associated with the machine. Also, measure the reach distance and hazard zone dimensions.
2. Consult Regulations and Standards. Look up specific guidelines for the type of machinery and hazard. Note any required measurements or calculations for guard placement.
3. Apply Safe Distance Formulas. Use standardized formulas to calculate the minimum safe distance.
4. Test Guard Placement. Temporarily install the guard at the calculated distance and evaluate its effectiveness. Ensure that the guard does not hinder productivity or access unnecessarily.
5. Train Employees. Educate operators and maintenance personnel on the purpose of the guard and the importance of maintaining its placement.
6. Periodic Review and Adjustment. Regularly inspect the guarding to ensure it remains properly placed as machinery or processes change.

Discover More Ways to Protect Personnel

Connect with the members of ProGMA for insights and assistance in determining appropriate machine guarding distance to hazard. They are also available to help end users, installers, integrators, machine users and others identify and mitigate potential risks within their operations.