The past few years have been marked by significant changes in industrial safety standards in the U.S. Safety managers, plant managers, and others who are not carefully monitoring these developments may not be keeping pace with the latest codes and regulations.
According to the Occupational Safety and Health Administration (OSHA), “machine guarding” that pertains to machines’ general requirements and general industry (29 CFR 1910.212) consistently falls in the top ten most frequently cited OSHA standards violated in any given year. When combined with newly introduced safety regulations, it is easy to understand why this commonly misunderstood topic is more confusing than ever. The multitude of robotic applications and the growth of robot use and automation in all industries only worsens the problem.
Conducting a thorough risk assessment is the best way to maintain a safe work environment, especially when adding new automated processes. Thanks to the new Robotic Industries Association (RIA) R15.06-2013 standard, proper risk assessments are no longer just a best practice; they are mandatory.
Adopted in May 2013, this new standard references ISO 10218-1 & 2, which addresses robots, robot systems, and integration. The new RIA 15.06-2013 was written to be compliant with international standards already in place in Europe, making life easier for manufacturers and end users. This new standard requires better hazard identification related not only to robotic motion, but also to the task being performed. Additionally, it requires validation and verification of the safety systems employed and requires designs that incorporate protective measures for the robot cell and the operator.
Some of the biggest changes in the new RIA 15.06 industrial robot standard have to do with safety-rated motion and allowing advanced programmable safety devices to be used. What this means is software will now be allowed “safety-rated” control of various aspects of the robot’s function, limiting the area in which the robot operates and the speed of robot motion. This is a departure from older standards in which programmable safety controls were not allowed.
In addition, as part of this standard, risk assessments are now required. Many professionals responsible for plant safety have been conducting risk assessments to increase safety as a matter of practice. These new regulations mandate risk assessments be conducted.
Understanding and assessing these risks—and ensuring compliance—is not a simple task. The first step for facility/safety professionals is to identify and understand all applicable codes and regulations for their facility and operation. Next, they should examine the prevailing machine guarding choices for those applications to validate their safety system and its components. Although many guarding methods and products are available, not all can be applied universally.
Every machine guarding application has a set of unique challenges and associated risk. The choices a facility manager makes for one application might not be the same, or appropriate, for the next. In most cases, safety-conscious managers would not guard an industrial robot the same way they would guard other equipment, because the risk associated with each differs greatly. Risk may even vary between similar operations, depending upon employee exposure and other factors.
When performing a proper risk assessment, point-of-operation guarding is the most involved aspect. It is easy to place perimeter guarding around the entire process. However, in most situations a machine operator needs to interact with the process by loading or unloading materials (such as metals to be welded) and “running” the machine.
This point-of-operation is where things get tricky. Many details must be considered when it comes to this area, including the layout or design of the process and the limits of the system. Also, facilities must properly identify all associated hazards and devise methods for hazard elimination and risk reduction.
Once the severity of the potential hazard has been determined, the frequency or duration of exposure and the possibility of eliminating or limiting exposure can help safety managers choose the proper machine guarding device. Also, using the distance formula identified in OSHA guidelines can help in this selection. Per this formula, the safeguarding device has a prescribed location based on a number of factors, including secondary hazards that might harm a machine operator.
Light curtains, laser scanners, and other presence-sensing devices are a commonly used and widely accepted method of machine guarding in manufacturing facilities from Tier 1 automotive to small machine shops and fabrication facilities. With presence-sensing, the automated process ceases once the safety device’s infrared beam is tripped.
In many instances these devices provide acceptable safety. However, they are not always the best choice in all applications, especially after a risk assessment is performed.
Curtains may be the right choice in some applications. However, fast-acting automated barrier doors or roll-up curtains may be better choices because they can eliminate exposure to both the dangerous movement of the machine and the secondary hazards produced by the process, such as smoke, flash, splash, mist, and flying debris. This further diminishes the potential risk and the severity of exposure.
Coupled with safety interlocks (up to PLe per EN ISO 13849-1 when integrated properly), automated barrier doors and roll-up curtains offer an increased level of protection for point-of-operation guarding. They restrict access to the process and contain secondary hazards of automated welding operations by placing a barrier between machine operators and machine movement.
These types of guards are an ideal alternative to light curtains and other presence-sensing devices in many situations.
Source: ISA News