Machine Guarding And Safety Hazards For Manufacturing Plant

Safety hazards

Discuss about the Machine Guarding and Safety Hazards for Manufacturing Plant.

Machine guarding is a safety mechanism in an engineering workshop or a manufacturing plant whereby, a shield or a device covers the dangerous areas or parts of a machine to avoid making contact with the human body or to prevent hazardous materials like sparks or chips from reaching the body. Machine guarding is usually the first line of defense, protecting workers and machine operators from harm while operating machinery in normal operations.  

It is among the most crucial concepts for safety in an industrial or manufacturing plant. If machine guarding is practiced properly, it will safeguard workers working with hazardous machines as well as those working in potentially dangerous work areas.

Safety hazards refer to unsafe conditions or factors that put a worker at risk of getting harm, injury, illness or even death (Parker et al., 2015). They are very common in workplaces. Each and every workplace has its safety hazard. Discussed below are some of the safety hazards experienced in workplaces.

These are cords, cables running on the floor. Fluid spills on the floor also cause this type of hazard. These hazards may block ways or make the floor of the working area slippery and may make workers fall down on the floor or on the machines (Parker et al., 2016).

Working from heights is a safety hazard. They include roofs, ladders, scaffolds or any other raised working area. Workers must, therefore, take precaution to avoid dangerously falling from the heights (Brauer., 2016).

Unguarded equipment especially the moving parts are a threat to the well-being of the worker. They include parts of the machinery, either moving or stationery that can be touched by the worker.

These are hazards related to the electrical connections of the work area and that of the machinery. They include bare cables, poor grounding, and improper wiring and many more. These electrical hazards may cause deadly electrocutions or burns on the operators or may even start a fire in the work area.   

Smaller work areas with no space allowance give the equipment operators little space to escape in case of an incident. Work areas should be spacious enough for the worker and allow room for an emergency escape (Yamin et al., 2014).

Certain radiation, especially the high-frequency radiations are harmful to humans. They include X-rays, gamma rays, UV radiation and many others. Workers should wear protective gear and stay away from radiation paths when operating such machines (Chinniah., 2015). 

Benefits of guarding

Certain work areas, for example, metal smelting industries, some work areas experience extremely high temperature. Workers must wear safety garments to keep safety in those environments. Same applies to extremely cold conditions.

Certain machinery operates with chemicals. These chemicals may cause breathing problems, skin irritation, illnesses or even deaths. Chemicals range from mild to explosive ones.

Though, some people are more sensitive to chemicals including the mild ones.

The human ear can accommodate sound up to some decibels, after which it becomes noise. Constant noise may lead to permanent damage to the ear. Workers working in work areas with constant loud noise should wear ear mugs for protection.

High-intensity laser beams are harmful to humans. They may cause permanent eye damage as well as skin irritation. Workers operating in high-intensity laser beam work areas should wear protective eyewear and cover body parts avoid laser accidents (Pavlovic and Fragassa., 2016).

The primary aim of machine guarding is to keep workers and other people safe from harm or injuries that may emanate from making contact with the machinery or flying debris or sparks.

In addition to safety, machine guarding also collects debris or sparks in a smaller area making cleaning easier. This is common in welding, painting and cutting machines.

Increased safety in a workstation reduces risks of getting injuries which in turn reduce downtimes that would be caused by injuries. In the long run, there is increased hours of production per day (Boyle., 2015). 

Presence of safety conditions in a work area tells the workers their safety is guaranteed.

This belief in safety creates a positive feeling towards working.

Having machine guards increase compliance with OSHA safety regulations, thus reducing chances of being fined.

The major disadvantage of machine guarding and other safety devices is the risk of control system malfunction. If this happens and the control system fails to trigger, the worker is in grave danger.

In addition, certain safety devices such as light curtains are placed at the entrance of work areas giving workers limited space to work on the machines without triggering the system.

Point guarding refers to a safety mechanism whereby, hazardous moving parts of a machine are shielded from making contact with the operators or whoever may move closer to the machine. These guards are usually fixed to the machine and the design is determined by the hazard type as well as the nearness of the hazard to the guard.

Disadvantages of guarding

In addition, point of operation guarding is the process of guarding the machine location, where the machine is operated. In summary, the primary reason of machine guarding is to protect machine operators from hazards, harm or danger that may be instigated by the machines or the operations of the machines.

Similarly, fixed barrier/perimeter guarding is an example of machine guarding. Barrier/perimeter guarding is a guarding mechanism whereby a barrier surrounds a work area of an automated system like the arm of a robot in a welding zone. This guarding system employs safety devices like pressure sensitive mats, light curtains or wire partition. The commonly used safety device for barrier guarding is wire partition. When they are used as machine guards they are either fixed in place on the machine or on the machine’s perimeter (Pinto., 2014). 

Modern day design of guarding, presence sensing and safety devices/machinery 

Presence sensing device is a safety device common for press brake safety. A press brake is a metal bending machine that has proven difficult to give protection to an operator. During operation, the one portion of a metal work-piece forms in a die while the other portion is held in one place by the operator. On detection of any foreign body, substance or object, the camera, laser or the light curtain devices immediately terminates the motion of the ram or retracts the die.

There are two categories of presence sensing devices (Farina et al., 2015). They are discussed below.

This type of presence sensing device uses cameras or laser beams to detect a foreign body or object or substance in the locality of the press brake. They give less obtrusion to users, thus users are not opposed to their use. An example of the laser beam safety device in electronic safety is the Laser Sentry Press which works together with a hydraulic press brake. It has high precision laser guides that directly surround the die while ensuring safety to the press brake operator. Similarly, press brake safety uses cameras for detecting intrusions between the lower and the upper dies. On detection of an intrusion, the downward ram motion is stopped by a signal. These cameras apply linear scales to compute the stopping distance and the position and velocity of the upper beam (Pollard et al., 2014).

This is another category of the (PSD) devices. It consists of technologies such as the light curtains. Light curtains project infrared beams around the perimeter of the equipment or the work area. The control circuit has a kill switch that is triggered to stop the equipment whenever there is a consecutive interruption on two or more adjacent infrared beams. Often, light curtains are mandatorily positioned in front of the work area.

Examples of guarding

These and other safety devices are connected to the control circuit of the equipment. They are then placed at the access points then configured to terminate operations of the equipment when triggered. The access points are fitted with hardware that is in full compliance with the occupational health and safety lockout/tagout regulations. This lockout/tagout hardware enables the equipment operator to lock the equipment I the terminated condition while conducting operations in the affected zone.

These are normally used alone or in combination with other guarding mechanisms. These light curtains focus beams or fields of light between opposite points. Breaking the beam or field at any point breaks the circuit it is connected to. They are preferred for application in sections where the operator directly interacts with the machinery to stop the equipment from moving while operating in the hazardous zone (Bluff., 2017).

These devices are connected to the control circuits of the machinery. They are then placed in the dangerous zones whereby if stepped on the machinery stopped. They can be used alone or combined with other guarding technologies to be more effective.

These devices can be used alone or with other devices such as light curtains or pressure sensitive mats. When used alone, they are placed or tied around the machine or the work area. 

In robotic welding, the welding cells include wire mesh fixed barriers and fitted with safety devices such as the light curtains, pressure sensitive mats as well as vinyl welding curtains (Nakayama and Jin., 2015). Each of these safety devices performs a specific task. The light curtain and the pressure sensitive mats stop welding activities when the operator is adding or collecting a weld fixture. While the vinyl welding curtains fixed within the fixed barrier regulate sparks and flash as well as spatters from the welds.

In robotic material handling, especially for pallet packing or de-palletizing uses any of the guarding systems mentioned above. Having pressure mats or light curtains surrounding the work area perimeter for stopping the robot when an operator gets in. In addition, wire partition with an interlocked gate could work by stopping the robot when the operator opens the gate (Jocelyn et al., 2016).

Still, in packaging, equipment for packaging like pallet wrappers contain a load that moves and an arm that stretches plastic wrap on the load. The wrapper is circled by a three-sided wire partition guard then a light curtain regulates entry to the open side preserved for a lift truck (Unnikrishnan et al., 2015).

Modern day design of guarding, presence sensing and safety devices/machinery

Conclusion

In summary, the primary reason of machine guarding is to protect machine operators from hazards, harm or danger that may be instigated by the machines or the operations of the machines.

Machine guarding promotes workshop safety and prevents accidents. Occupational health and safety regulations also require the use of guarding in industrial and manufacturing facilities. It is important for owners to comply to prevent fines, but most importantly to reduce or prevent harm and injuries.

References

Bluff, E., 2017. Safe Design and Construction of Machinery: Regulation, Practice and Performance. CRC Press.

Boyle, T., 2015. Health and safety: risk management. Routledge.

Brauer, R.L., 2016. Safety and health for engineers. John Wiley & Sons.

Chinniah, Y., 2015. Analysis and prevention of serious and fatal accidents related to moving parts of machinery. Safety science, 75, pp.163-173.

Farina, E., Bena, A. and Dotti, A., 2015. Impact on safety of a preventive intervention in metalworking micro-enterprises. Safety science, 71, pp.292-297.

Jin, G. and Nakayama, S., 2014, July. Virtual reality game for safety education. In Audio, Language and Image Processing (ICALIP), 2014 International Conference on(pp. 95-100). IEEE.

Jocelyn, S., Chinniah, Y. and Ouali, M.S., 2016. Contribution of dynamic experience feedback to the quantitative estimation of risks for preventing accidents: A proposed methodology for machinery safety. Safety science, 88, pp.64-75.

Nakayama, S. and Jin, G., 2015. Safety training: enhancing outcomes through virtual environments. Professional Safety, 60(2), p.34.

Parker, D.L., Yamin, S.C., Brosseau, L.M., Xi, M., Gordon, R., Most, I.G. and Stanley, R., 2015. National machine guarding program: Part 2. Safety management in small metal fabrication enterprises. American journal of industrial medicine, 58(11), pp.1184-1193.

Parker, D.L., Yamin, S.C., Brosseau, L.M., Xi, M., Gordon, R., Most, I.G. and Stanley, R., 2015. National machine guarding program: Part 1. Machine safeguarding practices in small metal fabrication businesses. American journal of industrial medicine, 58(11), pp.1174-1183.

Parker, D.L., Yamin, S.C., Xi, M., Brosseau, L.M., Gordon, R., Most, I.G. and Stanley, R., 2016. Findings from the National Machine Guarding Program–A Small Business Intervention: Machine Safety. Journal of occupational and environmental medicine, 58(9), p.885.

Parker, D.L., Yamin, S.C., Xi, M., Brosseau, L.M., Gordon, R., Most, I.G. and Stanley, R., 2016. Findings from the National Machine Guarding Program–A Small Business Intervention: Machine Safety. Journal of occupational and environmental medicine, 58(9), p.885.

Pavlovic, A. and Fragassa, C., 2016. Analysis of flexible barriers used as safety protection in woodworking. International Journal of Quality Research, 10(1), pp.71-88.

Pinto, A., 2014. QRAM a Qualitative Occupational Safety Risk Assessment Model for the construction industry that incorporate uncertainties by the use of fuzzy sets. Safety Science, 63, pp.57-76.

Pollard, J., Heberger, J. and G. Dempsey, P., 2014. Maintenance and repair injuries in US mining. Journal of Quality in Maintenance Engineering, 20(1), pp.20-31.

Unnikrishnan, S., Iqbal, R., Singh, A. and Nimkar, I.M., 2015. Safety management practices in small and medium enterprises in India. Safety and health at work, 6(1), pp.46-55.

Yamin, S.A.M.U.E.L., Parker, D.A.V.I.D., Brosseau, L.I.S.A., Gordon, B. and Xi, M., 2014. National Machine Guarding Program: design of a machine safety intervention. Safety Science Monitor (Sweden), 18(1), pp.1174-1183.