1.1.12 Machine guarding

Definition: “Guarded” means shielded, fenced, or enclosed by covers, casings, shields, troughs, spillways or railings, or guarded by position or location. Examples of guarding methods are guarding by location (positioning hazards so they are inaccessible to employees) and point of operation guarding (using barrier guards, two-hand tripping devices, electronic safety devices, or other such devices).

While OSHA’s penalties for machine guarding violations do not tell the whole story, they illustrate how much work remains in dealing with this “simple” problem with a scope that remains difficult to define. There is no doubt about it, machine and equipment guarding continues to challenge industry.

Unfortunately, the most common way to learn of a machine or equipment guarding shortcoming is when an injury occurs. Furthermore, accidents associated with improperly or inadequately guarded machines or equipment often produce more severe injuries.

The United States Bureau of Labour Statistics presents more disappointing data. Despite improvements during recent years, nearly 6,000 occupational amputations were recorded in the United States during 2009. Many of these amputations are products of improperly guarded machines or equipment or lockout violations.

Ignorance is no defence

While it is unknown how many of the referenced machine guarding injuries or violations were detected after the employer had taken action to adequately guard the equipment in question, the existence of such cases is well documented. For example:

  • An operator of a hydraulic press was crushed to death when he reached inside of the press to unload an assembly. The press was equipped with light curtains and fixed guards, and the employer had contracted design and installation of the guarding. The press utilised presence-sensing device initiation (PSDI) to automatically cycle the machine when the area protected by the light curtain was cleared. The press operator, who had a slight build, unintentionally moved inside of the light curtain, which signalled the press to cycle. The guarding was judged to be inadequate and improperly installed.
  • An operator of a machining centre with integrated robotics incurred a crushing injury that resulted in a leg amputation. The equipment had been used safely for many years and seemed totally enclosed by fencing and failsafe, interlocked gates. The guarding arrangement was designed by the machining centre manufacturer and installed by a plant maintenance crew. Parts were fed through an opening in the fenced enclosure by a powered work-holding fixture (pallet). The operator crawled through this small fence opening to make a “quick” adjustment when he sustained the injury. Prior to the incident, the fence opening was not considered as a viable means of ingress. Remedial action included installation of strategically placed light curtains around the fence opening.

Impact of improperly guarded equipment

While injured workers are the ultimate victims of accidents, their employers don’t escape unscathed, either. The business impacts of accidents and injury are both tangible and intangible. Cost leads the way in terms of tangible impacts, including increased workers’ compensation costs, OSHA penalties and legal fees.

Less tangible impacts can have even greater effect, however. When a worker suffers a serious injury, plants can expect:

  • Costly downtime while the investigation is completed. In some cases, investigations can take days or weeks before affected equipment can be returned to service following any required remediation. Downtime also can result in missed shipments and disappointed customers.
  • Increased overtime costs
  • Diversion of resources to address crises caused by the accident
  • Decreased employee morale or worker unrest
  • Negative publicity
  • Damaged reputation to the business – even recruiting efforts can be impaired

Root Problems

Obviously, businesses do not want their workers to be hurt, endure enforcement actions or bear additional cost. So why do machine guarding problems persist? Perhaps the topic is not as easy to understand as it may seem. Consider the following:

One has to consider a myriad of variables in defining the proper machine guarding solutions. First, the equipment not only has to be properly guarded, but it also must continue to serve its production demands. Proper guarding strategies must consider all variables – production, set-up, tool changes, inspection, maintenance and abnormal or upset conditions.

Over the last 4 decades, machine guarding has progressed from largely a mechanical undertaking to one that is more electronically focused. Much of the manual machinery that was being used 40 years ago has been replaced by highly automated, computer-controlled equipment. The number of interlocks and interfaces associated with properly guarding automated equipment is not easy to understand.

Newer equipment is sophisticated and is produced by a growing number of global companies. Too many purchasers of newer equipment incorrectly believe that the equipment manufacturer is responsible for proper machine guarding. Purchasers also can gain a false sense of confidence through requirements that equipment “must be guarded in accordance with OSHA standards.” The fact that an equipment manufacturer accepts this requirement does not mean that they understand how to properly guard the equipment.

Machine guarding is like other technical functions – new products, approaches and requirements are continuously introduced. Few people have the time – or the ability – to keep pace. While OSHA does not approve equipment, approval by third parties (e.g., UL, ANSI and NFPA) is required or recommended for many machine guarding components.

When manufacturing operations struggle with limited resources, they may assign machine guarding functions to whoever is available whenever they can fit it into their schedules. In some cases, this means that the workers assigned responsibility do not have the technical background needed to understand and apply the proper technology. It also can mean significant delays in completing the guarding task while waiting for an opening in the schedule, researching options and the trials and errors of installation. Unfortunately, even after going through this process, there is no guarantee that the work will be properly completed.

Even manufacturing companies with broad and deep engineering resources may find it difficult to divert their technical resources away from core functions.

Machine guarding is a niche specialty. Even the most competent of internal engineers faces a learning curve to understand the complexity of the OSHA standards and application of the many consensus standards that are involved.

Many companies take a hybrid approach to machine guarding. It is not uncommon for an internal employee to identify the guarding need through an informal review. That person then may work with a local industrial equipment firm to specify guarding hardware and software. Design may be contracted or handled by other internal or external resources, while yet another contractor or internal maintenance team may complete the installation.

In this case, it can be difficult to identify the accountable party in the event of a question or problem. If no member of the ad hoc team has in depth knowledge of machine guarding technologies and requirements, it’s also possible the original project objectives of properly guarding the equipment while maintaining optimum productivity will be lost.

The Holistic Solution

Holistic machine guarding approaches include:

  • Conducting professional risk assessments on a machine-by-machine basis. The guarding needs, including safety circuits, for each piece of equipment are specified in accordance with the most recent standards. Sizes, types and locations of recommended guards and devices are clearly illustrated. In addition, a quantifiable risk index is calculated for each piece of equipment to help the business owner prioritise the work. This risk index and its accompanying cost estimate also are useful for budgeting purposes.
  • Working with customer engineers, safety professionals, supervisors and workers to design an approach that fully satisfies all guarding requirements while meeting production needs
  • Specifying hardware and software solutions. At minimum, holistic machine guarding firms will specify only equipment that is listed by third parties and certified to relevant standards. These holistic firms manufacture many of their own guarding devices and have a broad, deep knowledge of the market and evolving standards.
  • Installation of guarding solutions by teams that are experienced with virtually every type of guarding application from the point of operation for presses, brakes and shears to perimeter guarding of manufacturing system cells. Installation typically is more efficient with less down time.
  • Commissioning guarding solutions in collaboration with the customer’s project team. Commissioning includes training for operators and maintenance personnel. Complete documentation is provided and all documentation and training is presented in the local language. Deep involvement by customer teams assures long-term satisfaction.

The comprehensive approach to machine guarding is useful when converting “zero injury” philosophies into reality.

The documented, machine-by-machine guarding risk assessments and the employee involvement fostered by the assessments directly support OSHA VPP recognition and OHSAS 18001 (Occupational Health and Safety Management System) registration efforts.

Holistic firms can work with equipment manufacturers to review and sanction guarding approaches for new equipment before it is shipped to the holistic firm’s customer.

Guarding designs and approaches can be used for identical pieces of equipment that may reside in multiple locations.

Machine guarding risk assessments can be used to qualify equipment for transfer from one country to another where different standards may be observed. Many emerging countries require such documentation before imported equipment can be sanctioned for use.

Consistent approaches to machine guarding results in better operation/maintenance and requires fewer spare parts in inventory. This is similar to the Southwest Airlines model of flying only Boeing 737s.