July 12, 2001
When people think of machine guarding, usually they think of devices to protect people from the moving parts on machinery.
When people think of machine guarding, usually they think of devices to protect people from the moving parts on machinery. While this is clearly one use of machine guarding, another area involves protecting workers from all types of cutting, welding, or grinding that can take place in tube or pipe cells.
Flying debris, weld flash, and other dangers make machine guarding an important component in the overall safety of a facility. But how do you choose the proper machine-guarding devices for your facility?
Because machine-guarding devices can do more than improve safety, it's important to understand the different types of machine-guarding options available. Properly applied devices can help improve workcell productivity, help eliminate ergonomic concerns, and improve the overall efficiency of a facility.
Because the amount of information on machine-guarding systems can be overwhelming, you'll find it easier first to examine closely your specific applications and needs. And, you can do it in just six steps.
Safety is the primary goal of any machine-guarding device, and you must look closely at safety in your work area. Are you concerned about flying debris, or do you simply want a process to stop when a person enters the work area? Are you concerned about weld flash? Is an automated process occurring in the cell? Consider all these issues before choosing a solution. When considering your machine-guarding options, always keep safety as your first goal.
Pay close attention to how materials are moved in and out of a workcell, and evaluate how a machine-guarding device could help or hinder that process. Can you use fixed devices, or are movable barriers necessary? Is automated equipment used, or does the application rely on people to complete the process? Look for opportunities to improve both productivity and safety.
While the term "machine-guarding device" implies that a barrier exists, not all devices provide a physical barrier to help protect employees from harm. Typically, you would use a physical barrier if flying objects are present that could harm employees. This includes the weld flash and debris from cutting or grinding that are common in tube or pipe cells.
If you want to improve your facility's productivity, the type of machine-guarding device you choose may have a direct impact. For example, an automated device can significantly improve workcell productivity versus a manual device, which requires a person to complete the operation.
While you might improve productivity by using a forklift to move objects in an operation, you could slow down productivity if an operator must exit that forklift to manually remove a machine-guarding device before entering a cell. This holds true for overhead cranes and conveyors as well. The productivity benefits realized by material handling devices will be lost by the human intervention required in the process.
Ergonomic problems can arise from the repetitive motion of opening or closing a manual machine-guarding device, even if the operation is done properly. Count the number of times this operation must take place on one of your machines and multiply the total by the number of work days a year.
An operation performed just a dozen times a day will add up to 3,120 times in a 260-day work year. Evaluate your own operation and talk to your employees to determine if a potential exists for ergonomic problems.
Once you understand the issues to consider, you then can look at the variety of devices available with a better understanding of your needs to determine the best solution for your operation. You'll find you have a number of options.
Nothing. You might find this hard to believe, but many facilities do not offer any protection to their employees. This can be a dangerous decision, as unprotected work processes may result in flying debris or weld flash, which can cause serious injuries.
Fixed Solid Guarding. The obvious benefit of a solid guard is that it provides a barrier between personnel and a hazard. This is ideal if you want to prevent access to a workcell completely. Unfortunately, because these devices are fixed and unmovable, they can hinder productivity if objects must move in and out of a cell.
Fixed guards are recommended for use around a workcell, but consider other guards for the opening, where material or an operator must move in and out.
Fixed Fencing. Although fixed fencing may seem to have the same benefits as a fixed solid guard, it doesn't protect from flying objects or flash. A fence does a good job of preventing access to a cell, but it isn't recommended for welding, grinding, or cutting areas, which are prone to flying debris. Again, fixed fencing is recommended for use around the workcell, but another device should be considered for the opening of the cell.
Safety Mats. Safety mats are used to stop an automated activity, such as welding or cutting, when a person steps on the mat. The mat sends a signal to the machine to stop, which protects the person from the potential hazards of the operating machine.
While safety mats are useful in preventing a person from getting too close to an automated process, they don't provide a physical barrier. And, though safety mats are automated, they can hinder productivity.
If people working around a cell step on the mat several times a day, the automated operation stops that many times, so safety mats often are used with other machine-guarding devices such as a physical barrier.
Light Curtains. These curtains use light beam technology to provide an invisible barrier to the hazards inside a workcell. When the light beam is broken, the automated activity inside the cell stops.
Unfortunately, the barrier is invisible, so it doesn't provide a physical barrier to hazards. In addition, light beam technology can be unreliable in dusty or dirty environments, causing false signals. A dirty light curtain may imitate the effect of a broken beam and stop the operation.
Manual Curtains and Barriers. Manual curtains and manual barriers provide a movable physical barrier between personnel and the hazard. This can be considered an advantage over fixed barriers, which can hinder productivity, and over light curtains and safety mats, which do not provide a physical barrier. Manual devices include rollup curtains, sliding curtains, and sliding hard panels.
The greatest limitation of manual barriers is that they require human intervention to open them and stop the automated operation in the cell. This human operation not only can slow productivity, but raises safety concerns if operators don't follow proper procedures.
To protect employees, safeguards must be in place to prevent them from opening the curtain before the automated activity stops. And, ergonomic issues could arise from the repetitive action of opening and closing the curtain or barrier, depending on how much effort is required.
Automated Machine-guarding Systems. The latest development in machine-guarding devices is automated systems, which offer the benefits of the other devices, without the disadvantages. Automated solutions include rollup curtains and barriers, pneumatic sliding curtains, and bottomup hard panel devices, which are custom-made to fit specific application requirements.
These systems provide a physical barrier between personnel and hazards and are connected to the automated activity in the cell for reliability and safety. This means the barrier won't open unless the activity in a cell has stopped, and the activity won't begin until the barrier is closed.
Automated systems also work well with material handling equipment, such as forklifts, overhead cranes, or conveyors. The machine-guarding system can open automatically without the need for human intervention. This complete automation of the cell process can help improve a facility's productivity and safety, and can help eliminate the ergonomic concerns associated with manual devices.
By installing the proper machine-guarding solutions for your operation, you can improve safety and productivity, while lowering long-term costs. By doing your homework first to determine what your needs are and what options you have, you'll be able to save yourself time, effort, and money and provide effective safety measures for your employees.
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