Robot Safety, Everything But Routine
| By: Tanya M. Anandan, Contributing Editor
Robot safety is always top of mind with industry advocates. For they know the robot’s power and understand its capabilities. Robots demand respect. Like any tool, when used improperly or without sufficient knowledge, they can be dangerous. Even fatal. Yet, let’s not forget the facts.
The fact is robot deaths are rare.
Over a 30-year span 37 robot-related accidents occurred, according to a search of OSHA incident reports. Of that number between 1984 and 2013, 27 incidents resulted in a worker’s death.
Compare this to the 4,585 workplace fatalities in 2013 alone, according to the U.S. Bureau of Labor statistics. Robot-related fatalities represent a mere fraction of all workplace deaths.
Still, one death is too many.
Especially in light of recent events, following a tragic fatality involving a robot at a German automaker in June (and as we went to press, a fatal accident in India). Pouncing on the news, some media sources responded with a torrent of hype, misguided speculation, and apocalyptic stories of killer robots.
Sticking to the facts, Patrick Davison, Director of Standards Development for the Robotic Industries Association (RIA), posted an official response, How Does the Accident in Germany Affect Industrial Robot Safety?
As noted by OSHA and cited in Davison’s article, many robot accidents occur during non-routine tasks.
“It’s very unlikely for serious injuries to happen during production,” says Davison. “Accidents usually occur during installation, maintenance and troubleshooting activities. But we don’t spend enough time talking about this area.”
Davison notes four OSHA provisions integral to the discussion on robot safety, especially during “programming, maintenance, testing, setup, or adjustment” where unintended operations could result in injuries:
- Control of Hazardous Energy (Lockout/Tagout)
- Risk Assessment
“When you start talking about any sort of maintenance activity, one of the first things that is brought up is lockout/tagout,” says Davison. “Controversy arises because nobody can agree on what lockout/tagout actually is and when it has to be implemented.”
The Lockout/Tagout Debate
OSHA Standard 29 CFR 1910.147 for control of hazardous energy, or lockout/tagout (LOTO), is designed to prevent injuries to workers from the unexpected startup of energized equipment or release of stored energy during machine maintenance. OSHA’s Lockout/Tagout Fact Sheet and the full standard are readily available online.
Basically, lockout/tagout requires that you remove the hazardous energy source associated with a machine before performing maintenance activities. In the case of an electric machine, this is usually done by removing the power source or unplugging it. Other sources of energy or stored energy can include pneumatic, hydraulic and mechanical, such as plant air or a spring under tension.
After disconnecting the power source, then you put a lock on that disconnect so that someone cannot power it up without removing the lock. You also put a tag on the lock identifying the individual that engaged the lock (the worker servicing the machine) and indicating that only this individual can remove the lock.
Davison says the requirements by themselves are clear and definitive. However, with robot cells and other more complex industrial processes, LOTO is open for sufficient debate.
“The problem with lockout/tagout is that there are a lot of tasks where you need power to the robot in order to do the job, such as programming,” says Davison. “You can’t program a robot if it’s not powered up.”
Programming, setup and troubleshooting – when robots often need to be powered up – call for extra vigilance. Long-time veterans of the machine safety industry know this all too well.
“I have this unfortunate distinction of having done more than 80 fatality investigations,” says Mike Taubitz, speaking from his home office in Fenton, Michigan, where he serves as Senior Advisor for FDRsafety LLC, a safety and health consultancy based in Franklin, Tennessee.
“That doesn’t even count the serious injuries,” says Taubitz. “In almost all cases, and this is something we’re slowly awakening to in the safety profession, these occur during the breakdowns, the nonscheduled, non-routine maintenance tasks. I call them the ‘Oh crap!’ moments. Something quit working, something went wrong.”
Taubitz is retired from General Motors, where he held every safety position from Plant Safety Supervisor to Global Safety Director during his 40-plus years with the automaker. He is internationally renowned for his expertise in machine guarding, and is an advocate and noted speaker on lean manufacturing and its relationship to safety and sustainability.
Control of Hazardous Energy vs. Zero Energy
Taubitz attributes the ongoing LOTO debate to several myths and misconceptions. He specifically notes how control of hazardous energy is often confused for a zero-energy state.
“It stems from the belief that lockout demands zero energy, not the control of hazardous energy,” says Taubitz. “There’s a huge difference.
“Not only does the regulation not use those words, it’s not in the preamble of the regulation and it’s not in the 136-page compliance bulletin.”
Taubitz also cautions against a zero-risk mentality and offers this analogy.
“Go tell your mechanic that you don’t want him to have the engine running with the hood open because he might get his fingers caught in moving parts. He’s going to look at you and say, ‘I can’t do my job.’ The engine has to be running to do troubleshooting and diagnostics.
“In probably 95 percent of all maintenance tasks where there’s been a breakdown, we will need to have power on at some point in time. That’s why we have to rely so heavily on the training, skills, and judgment of people to know when to shut down and do full lockout for control of hazardous energy.”
Doug Huston, Project Manager for Genesis Systems Group LLC, knows firsthand the importance of robot safety. He is often the one potentially in harm’s way.
“Most of the accidents happen in the troubleshooting phases when you’re trying to figure out what’s going on, or programming the robot cell,” says Huston. “I still have my hand on pendants today, so I fully understand that.”
Genesis is an RIA Certified Robot Integrator located in Davenport, Iowa. As one of the largest automated solutions providers in North America, Genesis specializes in the design, manufacture, and implementation of robotic systems for welding, material handling, machine tending, abrasive waterjet cutting, and material finishing. Industries served include automotive, rail, agricultural, defense and aerospace.
“When the system is not in ‘production,’ whether it be at the initial deployment or for maintenance, deliberate attention is required of trained personnel familiar with the hazards unique to this mode,” says Huston. “Robots have features to ensure this work can be done with minimum hazard.”
In these cases, the automated cell is typically already at the end user’s location and the robot is powered up.
“Another common task is simply touching up,” says Huston. “The programmer or operator of the machine goes into the cell to do a quick touch-up. A lot of times, they are in a hurry for a production run and they will do things in such a hurry that they put themselves in harm’s way.”
Safeguarding for Safe Maintenance
RIA’s Davison stresses the importance of designing your safeguarding systems so there is adequate access to do preventative maintenance tasks. You don’t want to have to defeat the safeguarding in order to do a job.
Taubitz agrees, citing poorly designed machinery or cells as one of the contributors to workplace accidents, and not just robot-related accidents.
“Two years ago, I was called into a large Tier 1 supplier in the Detroit area where a female employee had been injured,” he explains. “During the investigation, we found that the maintenance worker had spent 40 minutes disabling the interlock. When the operator entered the robot cell, the robot wasn’t turned off and it activated. Thank goodness, she wasn’t seriously injured.
“Management came in with the belief that you can never defeat an interlock,” Taubitz continues. “I said great, go tell corporate that you’re never going to run again. It took me a few times to get through to the plant manager that when the operator went through the interlocked gate, it shut down all the power. This woman had to go in and master a gauge. Well, you need power to the gauge. The cell wasn’t designed properly.
“The serious and fatal injuries happen to the mechanics and electricians, the skilled workers and others that do work outside of normal production. Yes, we protect them with lockout, confined space and fall hazards, and general procedures, but the design of machinery and equipment I find typically fails in providing easy access so they can get the work done safely, quickly, and without having to defeat the safeguarding we put in place.”
“If a specific safeguard prevents the robot user from running the machine the way they want to, they will look to defeat that safety without always understanding the ramifications,” says Genesis’ Huston. “This is why it is so important for the customer to understand the intent of all safety components.”
Genesis designs robot cells with this human variable in mind.
In the pictured robot cell, the configuration allows the programmer and/or maintenance personnel complete access to the front of the machine. If the programmer needs to do a touch-up, the operator is able to stand in front of the machine where he or she is not trapped by the fixed guards. Other safety features include roll-up barriers, light curtains, gate switches, and safety software to protect workers that will maintenance the machine.
Huston says simple tasks that might cause operators to bypass safeguards include changing a torch liner or removing a bird nest from the wire feeder when it gets backed up.
“Another way Genesis’ cell design keeps the operator free from harm is that energy is not stored on the weld fixture where the operator loads the machine,” he explains. “Clearly labeled e-stops inside and outside of the cell also make it easy to stop the machine in case of any emergencies.”
This video shows a similar two-station robotic welding cell providing for safer robot programming and maintenance.
Another way robot safety is getting easier to implement and sustain is through safety-rated soft axis and space limiting technology, a feature becoming more common in the latest robot controllers.
“Soft axis and space limiting and position monitoring of the robot arm gives you a lot more control on the safety side of things,” says Huston. “You don’t have to make the fences as large, and you can still protect the operator and maintain the 20 inches around the workspace.”
For more information about safety-rated soft axis and space limiting technology, and its many advantages, see The Shrinking Footprint of Robot Safety.
Risk Assessment for Maintenance Tasks
Risk assessment is one of the key OSHA provisions and a vital element in the ANSI/RIA R15.06-2012 robot safety standard. Davison can’t stress this enough.
Every discussion on safety always comes down to the bottom line: Do a risk assessment.
“The risk assessment should include maintenance and related types of tasks,” says Davison. “The integrator performing the risk assessment must make sure the robot end user is involved in the process and aware of the proper procedures documented in the risk assessment as it relates to maintenance.”
“The maintenance team and programmers need to work closely together and understand the machine and the 15.06 standard,” says Genesis’ Huston. “A lot of times we pass that knowledge down with the risk assessment, so that the end user knows the intent of the machine and the safeguards that we’ve put in place.”
Huston says they have a team in-house that does all of their risk assessments. “The project manager, engineers and designers that are working on a project usually sit in on those risk assessments, so that the people designing and working around that machine are all on the same page and understand the end goal.”
Task-Based Risk Assessment
Taubitz advocates for task-based risk assessment (TaBRA), a process he says is a recognized methodology by OSHA. Task-based risk assessment focuses on the kinds of tasks required, both routine and non-routine, and the risks associated with those specific tasks.
“Task-based risk assessment came about in the late ‘90s at General Motors in collaboration with the United Auto Workers (UAW),” explains Taubitz. “We would first define the needs of the task. So if I need power, full power, some of the power, or power to some part of the operation, I will recognize it and then assess risk.”
He says TaBRA is fundamentally different from conventional methods of assessing worker risk. It requires asking the right questions to understand the tasks of ALL workers, especially those performing maintenance and other non-routine tasks.
“Instead of standing around with a bunch of experts saying here are the hazards and here’s what the safeties are, they approach it from the perspective of the worker, by understanding what work has to be done and under what conditions. This doesn’t excuse people that try to take shortcuts. But what we usually call a shortcut I find is oftentimes an absolute task requirement, and we either didn’t ask the right question or our biases prevent us from asking the right question.
“Now we’re trying to recognize that it’s the interface of the human beings, not just the hazard, but what are the hazardous situations?”
Taubitz says it’s just as important to ask the right question after an interlock or some other safeguarding device has been bypassed.
According to Taubitz, task-based risk assessment became a cornerstone at General Motors. “Mike Douglas, Manager of Engineering for Health and Safety and his UAW colleagues really brought the tool and thinking into prominence,” he says. “They fed it into the ANSI B11 series of standards for general industry. It shows up throughout RIA and the ISO standards.”
Taubitz says the onus falls on the robot integrator and it has to be a shared responsibility with the robot end user.
“It’s the robot integrator’s main role to pull things together because they are the one with the expertise. They have selected the proper robot, they’re guiding the user. The integrator, at the competitive bid stage, should be asking what tasks you anticipate being done. How will you operate this process if the robot breaks down? Those are questions that would force a user who might not have thought of certain situations to begin to address them.
“If a safety consultant is needed, I hope it’s someone well-versed in all of the standards and in risk assessment, and bottom line, not trying to shoot for zero risk,” he adds. “When you shoot for zero risk, you will increase risk.”
Training the Robot User
RIA’s Davison stresses the importance of training. He says it’s important to know the safe operating procedures and when to apply lockout/tagout.
“A well-trained worker will know the difference between a machine stopping as part of normal operation and a machine stopping due to a fault,” he says. “Providing training to know when and when not to intervene, and how to intervene safely is extremely important to keep workers safe.”
Again, the responsibility often starts with the integrator. They have to train the robot end user. But then the end user needs to follow through by reinforcing the safety procedures in practice.
“As the integrator, we need to make sure that we’re communicating the intended use of that machine to our customer and our end user,” says Genesis’ Huston. “It’s when you stray from the intended use of the machine, that’s when accidents happen. When they try to do things with the machine that it wasn’t designed to do. It’s really when you don’t know the power and speed of the equipment that you underestimate it and could get hurt.
“Our job as an integrator is to provide our customer with safety first, then balance cost and floor space to provide the machine that they need and still make it affordable, useful and safe.”
Knowing Your Risk
So where does the end user’s responsibility lie? Huston says it’s after they take possession of the robot cell.
“They get the machine. We have done our risk assessment in-house. At that point, the end user needs to complete their risk assessment.”
He says this is particularly applicable to small and medium-sized businesses that often overlook risk assessments.
“I think one of the best practices that may not be used in smaller facilities is a risk assessment,” says Huston. “It’s a very good tool to use during the design, engineering and production phases, so everybody really understands what’s in front of them and how that machine can hurt them. A lot of times the training that needs to happen internally is driven by that risk assessment.”
With record numbers of robots installed and more companies, large and small, dipping their toes into the automation waters, operating procedures that maximize productivity without sacrificing safety become even more critical. Take a closer look at your safety procedures, especially those for non-routine maintenance and troubleshooting tasks. Stay safe.
For more information on robot safety standards, training and certification, visit RIA’s Safety Resources page.