Figure 5 A safeguarding system installer inspects an electrically interlocked rolling gate to allow access for coil loading. Images provided

Machine operators suffer approximately 18,000 injuries and 800 deaths per yeara stat from ICW Insurance Companiesand year after year, machine guarding violations show up on OSHAs top 10 list of most frequent citations. Considering OSHAs recent renewal of its National Emphasis Program on amputations targeting metalworking manufacturers and the ever-increasing costs related to employee injuries, fabricators have a strong incentive to implement a rigorous and consistent machine guarding program.

The challenge is putting together an organized, systematic machine safeguarding plan. The task can be daunting given the typical manufacturing facility that has machines of varying years of manufacture and function. Which machines pose the greatest danger? What tasks should be eliminated or modified because they put employees in unacceptably hazardous situations? How do companies begin to determine what hazards their machines present and how should they be mitigated?

The best and most effective way to tackle this overwhelming task is to understand where the hazards are, why they exist, and how frequently employees are exposed to them. Once companies know where their exposures lie, they can then determine the best course of action to mitigate risks.

The following four-stage, methodical approach can lead to a successful and dynamic safeguarding program. It begins with a machine guarding survey that serves as a high-level triage and helps prioritize projects. Stage 2 is a machine-specific risk assessment, and stage 3 addresses the mitigation of the identified risks. The final stage implements the well-thought-out design and involves operator training (or retraining) on how to work with rather than around the new safeguarding.

A full facility review often performed by a third party, the machine guarding survey typically takes a day or two on-site. Outside evaluators, who havent seen the operation day in and day out, offer fresh experienced eyes and typically are more critical of a companys processes. The surveyors spend five to 10 minutes per machine evaluating the status of six key elements of machine safety (see Figure 1).

Each element is given a score, and the combined total is used to determine what level of priorityhigh, medium, or lowneeds to be given to that machine. Machines with a score greater than 40 are considered high priority and warrant an additional formal risk assessment or, in some cases, immediate safeguarding.

The survey does not consider the severity of harm for the identified hazards. For example, an unguarded machine may receive a high survey score because of a missing guard, but the subsequent risk assessment determines that the actual risks that unguarded machine creates are low, because the hazards have little chance of injuring an operator severely.

The term risk assessment is often used in a generic sense; some use it to describe the guarding survey in Stage 1. Multiple definitions of risk assessment can be found in various documents, including those from the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO). OSHA calls the process a job hazard analysis.

Regardless, in the current context the risk assessment differs from the machine guarding survey in its depth of investigation and its ultimate purpose determining whether identified risks are acceptable and how unacceptable risks can be mitigated. The goal is to reduce unacceptable risks to an acceptable level.

The machine guarding risk assessment should involve a broad team, including top managers, floor supervisors (production, operation, maintenance, and setup personnel), machine operators, and an outside safeguarding professional. Each plays a critical role and brings unique perspective.

Figure 1 Six questions provide insight into a machine's safety fitness.

The project must involve top managers who can commit the proper resources. Without buy-in from the top of an organization, any safeguarding program is doomed to fail from insufficient support and a lack of proper funding.

The floor supervisor knows how things actually work in the shop. Many safeguards, once implemented, impede work flow because operational variables best understood by the supervisor are not distilled into the design. The floor manager voices his or her opinion about whether a given safeguarding scheme will impede or enhance throughput.

Machine operators best understand the intricacies of each machine and manufacturing process, and their input into safeguarding requirements is invaluable. Ultimately, they must use the safeguarding system successfully and not be compelled to circumvent it.

Outside safeguarding professionals bring a range of expertise in applicable standards and regulations. They should have a deep knowledge of safeguarding technology, and they should be relied upon to do a correct installation and retrofit of the safeguarding system.

Companies in different industries use different risk assessment systems and platforms. The most widely recognized are found in several documents: for domestic machinery, ANSI B11.0, Safety of Machinery, General Requirements and Risk Assessment; and for global machinery, ISO 12100, Safety of Machinery General Principles for Design Risk Assessment and Risk Reduction, and ISO 13849-1, Safety of Machinery. Each offers a series of logical steps to systematically examine the hazards associated with machinery, and each has examples of risk scoring systems that assess the required level of hazard mitigation (see Figures 2 and 3).

With these tools, those performing the assessment gather information about the machine, identify the tasks performed, and score the hazard associated with each. They then determine if those hazards are acceptable or not. If they are not acceptable, they move on to Stages 3 and 4, designing and implementing protective measures to reduce the unacceptable risks to an acceptable level. Any risk determined to be acceptable at this point should be mitigated through administrative measures such as operation-specific training.

Both the machine guarding survey and the machine guarding risk assessment should be treated as living documents. As machines are cycled in and out of the shop or are repurposed, these documents must be updated to reflect the changed environment.

The design stage considers all that has been learned in the previous two stages. If it doesnt, the possibility of a safeguard inadequately reducing risk or rendering a critical task undoable is tremendously high.

Consider a fabricator and stamper that, after having gone through a machine guarding review, found that it had an automated coil slitting line with multiple hazards. Existing guarding was minimal. A deep-dive machine guarding risk assessment identified several unacceptable hazards.

The goal was to maximize safety without compromising efficiency. The line was divided into sections(1) coil loading and decoiling, (2) slitting, (3) pit and wiping, (4) recoiling, and (5) slit-coil unloadingand all five had unacceptable hazards. Considering this, the best solution was to design a perimeter fence enclosure for the entire line (see Figure 4). No individuals would be permitted within the guarded area. The design lowered risk to acceptable levels, but it needed to be customized because it prevented operators from performing necessary tasks.

Figure 2 This risk scoring system is based on the one described in ANSI B11.0, table 2.

To keep residual risks at acceptable levels, the safeguarding design needed to allow access inside the enclosure only during controlled conditions. Operators also needed to change how they performed some of their tasks.

Coil Loading and Decoiling. For instance, to allow a forklift to load the unslit coil onto a coil car, a large rolling gate was added to the perimeter fence (see Figure 5).
To prevent the line from operating when the gate was opened and the coil was being loaded, the gate was electrically interlocked. With the coil loaded onto the car, an operator used a hold-to-run pendant to drive the coil car to the decoiling reel. The operator never rode on the car itself, and the residual risks created by the coil car movements were deemed acceptable. That said, to do the job properly, the operator needed to be close enough to observe the coil car as it approached the reel and transferred the coil. That meant he needed to be within the enclosure. To allow him to do this, an interlocked human access door was also added.

Slitting. To ensure proper alignment when threading the coil, the operator needed to watch the edge of the coil closely as it entered the slitting knives. An interlocked human access door was added to allow easy entry from the control console outside the perimeter guarding. Inside the controlled area and with the door open, the operator could activate an enable switch and a hold-to-run pendant to jog the coil. This required the main control system to be modified to allow only jog-mode operation when the door was open and the enable switch activated.

Pit and Wiping. After the material exited the slitting knives, it dropped into a pit and then into a wiping operation that cleaned the material before recoiling. Wiping pad pressure was maintained with an air cylinder, adjusted regularly during operation. The operator also needed to observe the wiping operation to know when to make the adjustment and watch the slit material while it traveled through the pit. The safeguarding solution moved the pressure adjustment valve outside the fencing and added a camera system so that the operator could observe at a station outside the enclosure.

Recoiling. During setup, the operator needed to guide the slit material onto the recoiling arbor while inside the enclosure, so a second enable switch and hold-to-run pendant station was added at this location to provide for this. Operators also monitored recoiled material tension during regular operation, so a second camera system was added for this purpose, allowing operators to observe the material through a monitor at the control console.

Slit-coil Unloading. The now recoiled slit material was unloaded by forklift and taken to the next operation. Limited spacing made it impossible to add another rolling gate. Instead, a large gap in the fencing allowed the forklift to access the recoiling arbor, and a safety laser scanner guarded the gap. Whenever something or someone was detected within the scanned area, the line was prevented from running.

After the safeguarding installation, operators could continue to function productively, yet at lower risk. Thats the ideal of a properly safeguarded system.

What made it possible? First, the installation crew worked with a detailed plan with clear instructions on how the safeguards should function. They documented changes to existing machine controls clearly and accurately. And because operators were involved early in the process, training was simple.

An organized approach makes safeguarding installation less disruptive. Triaging helps address the most hazardous operations first, and the four-stage approach helps prioritize hazards thoroughly and objectively.

Such a detailed approach to safety should help any manufacturer create a successfully guarded shop. The ideal guarding makes jobs both safe and easy, so that operators will want to work with the machine guards rather than around them. After all, working around poorly designed safeguards can be more dangerous than having no safeguards at all.

Douglas Raff is a Certified Machinery Safety Expert (TV Nord) and an owner of Paragon Industrial Controls Inc. As a member of the Safety Council within the Fabricators & Manufacturers Association (FMA), Raff conducts safety certificate and other educational courses for FMA and other organizations.

Continued here:
The anatomy of a machine safeguarding project - The Fabricator