Machines both have mechanical and non-mechanical parts that can cause injuries including minor abrasions, cuts, and burns to severe accidents such as lacerations, fractures, and even amputation. To protect your workers from unfortunate incidents such as these, installing adequate safeguards on your machinery is important.
You can use several types of machine safeguarding, but how do you make sure that you are choosing the appropriate ones? Here, we discuss the 5 types of machine safeguards in detail including the parts of a machine that must be guarded. This ensures that you choose the most effective and practical method.
What is Machine Guarding?
First of all, what is the purpose of machine safeguarding? It is to prevent injuries caused by machine-related hazards (we will discuss the types later in this article). Any machine should be considered dangerous and can create hazards in the working area. By installing the right safety guards, you can reduce or even eliminate these hazards.
The Occupational Safety and Health Administration (OSHA) standards require you to guard any part of a machine including processes or functions that could injure people.
5 Types of Machine Safeguards
There are five major types of machine guarding that you can use to protect your workers in the machine’s immediate vicinity:
1. Guards
These are basically physical barriers that prevent direct contact between your workers and the machine’s dangerous parts by enclosing hazard-causing components. This is why they are often preferred more than other methods.
Guards are typically designed with lock fasteners, bolts, and screws and require a tool to remove them. Though they are physical barriers, they are generally designed to not obstruct the machine operator’s view and prevent workers from doing their job.
Common types are fence guards, gate guards, and door guards.
General Classifications of Machine Guards
There are four general types of guards:
| Fixed Guards | – Permanent guards that can’t be moved and don’t consist of moving parts. – Their function doesn’t depend on the machine’s moving parts. – Preferred compared to other types due to its simplicity. – Since they are permanent, they need to be removed for maintenance tasks which will require a trained staff. |
| Adjustable Guards | – Permanent barriers that you can manually adjust and lock to handle different material sizes. – Employees using them should be well-trained as improperly adjusted/locked guards could fail and cause fatal injuries rather than protecting your workers. |
| Self-Adjusting Guards | – They work the same way as adjustable barriers, but they automatically adjust based on the stock’s size. – Common on woodworking tools and table saws. |
| Interlocking Guards | – Also called barrier guards that shut off or disengage power, stop moving components, and prevent the machine from starting when they are open. – Placed around hazardous components of machines that are accessed often because they allow you to safely access the machine’s interior parts without total disassembly. |
You can read a more detailed discussion of the pros and cons of each on OSHA’s introduction to guards.
2. Devices
These safety devices can do one of the following functions to keep the machine operator away from the danger area:
- Stop the machinery if any body part (like a hand) is unintentionally placed in the hazard area.
- Create a barrier that synchronizes with the machine’s operating cycle to prevent workers from entering the hazard area.
- Require the use of both hands for controlling the machine to keep the body and hands safe.
- Withdraw or restrain the operator’s hands during dangerous machine operations.
Types of Devices
Many devices use different controls or sensors to limit the operator’s risk exposure. These types include the following:
| Photoelectric | – Uses light sources and controls that stop the machine’s operation when interrupted. – Machine braking activates when the light field is broken. |
| Radiofrequency | – Use capacitance fields that stop the machine from operating when interrupted. – Any disturbance on the field activates machine braking. |
| Electromechanical | – Consists of a probe or bar that descends when a machine cycle is initiated. – Any obstruction preventing the probe/bar from descending stops the machine cycle. |
| Pullback | – Uses cables that are connected to the arms, wrists, and/or hands of the operator. – Pulls the operator’s arms out when the machine starts to cycle – Installed on machines that involve stroking actions. |
| Restraint or Hold-Back | – The device uses straps or cables that are connected to the hands of the operator and restricts their movement within a safe area. |
| Safety Trip Controls | – They use pressure-sensitive bars that stop the machine when a worker accidentally trips or loses balance and applies pressure to the bar. |
| Two-Hand Control | – Requires operators to concurrently use both of their hands and apply constant pressure to the control buttons before the machine starts to operate |
| Two-Hand Trip | – Requires operators to use both of their hands on two trigger buttons to start the machine. – Usually used on machines with full-revolution clutches |
| Gate | – Creates a movable barrier to protect personnel before the machine starts. |
Read more about each type of device and their pros and cons on OSHA’s introduction to devices.
3. Machine Location/Distance
This method involves locating the machine and its hazardous moving parts and ensuring they are away from the operator or working area. Making dangerous parts inaccessible during machine operation prevents accidents.
4. Automated Feeding & Ejection Methods
Guards will still be required, but eliminating the involvement of operators in the hazard area by using automated feeding and ejection methods enhances worker protection. Using robots to load and unload stocks, transfer objects, assemble parts, and perform other actions are some applications. These are ideal in high-production tasks that involve repeated routines.
5. Miscellaneous Aids
Miscellaneous aids can’t provide complete protection against machine hazards, but they can offer enhanced safety by protecting workers in the machine’s immediate vicinity. Examples are:
- Awareness barriers that warn workers about hazards
- Protective shields that contain flying debris like chips, sparks, and sprays
- Hand-feeding tools that workers can use for handling materials that go into the point of operation
Factors That Affect the Type of Machine Safeguard You Should Install
The machine safeguard you should use along with the design will depend on the following factors:
- The machine’s operation type
- The stock’s size, shape, and material
- Handling method
- The working area’s layout
- Production limitations or requirements
NOTE:
- You can install more than one safeguarding tool to enhance operator safety, but they should work properly together to avoid machine guarding accidents.
- The guard’s material and design will depend on the machine.
Types of Hazards: Which Parts of a Machine Must Be Guarded?
Hazard identification is the very first step you need to do when planning for workplace safety. Here are the major categories of hazardous mechanical motions and actions of machines that will need safeguarding:
Hazardous Motions
| Rotating Motions | – Rotating parts can grip clothes and force your workers’ arms into dangerous positions through mere contact with the skin- Examples are vertical or horizontal shafting, spindles, shaft ends, clutches, flywheels, cams, couplings, and collars- Exposed bolts, nicks, setscrews, or abrasions on these parts increase their danger |
| Reciprocating Motions | – Parts that make up-and-down or back-and-forth actions that can accidentally hit or catch a person |
| Transversing Motions | – Parts that move in straight lines and can hit or catch a person |
| In-Running Nip Points | Hazards caused by: – Rotating parts with meshed gears, calendars, and rolling mills – Tangentially moving and rotating parts like power transmission belts and their pulleys – Fixed and rotating parts – Spoked hand wheels – Screw conveyors, etc. |
Hazardous Actions
| Cutting Actions | – Involve rotating, transversing, or reciprocating motions that could cause injuries |
| Punching Actions | – Actions that involve applying power to a ram/slide for stamping, drawing, or blanking stocks |
| Bending Actions | – Similar to punching actions but they are for stamping or drawing stocks only |
| Shearing | – Dangers are in areas where stocks are inserted, held, and withdrawn |
Other non-mechanical hazards include debris, chips, flying splinters, sparks, splashes, or sprays.
You can find more details on specific machine hazards and safeguarding methods here as well as a more comprehensive discussion of machine safeguarding requirements here.
FAQs
The primary methods are guards and devices which are used to greatly reduce or prevent amputation injuries.
OSHA specified three fundamental areas that all machines have:
1. Point of Operation – Points where any work is done like cutting, shaping, and others.
2. Power Transmission Components – Any component that transfers energy like pulleys, belts, gears, spindles, flywheels, cranks, chains, and couplings.
3. Operating Controls – Any part that moves like rotating parts, auxiliary parts, and feed mechanisms.
Take note that machines may have these basic components but their safeguarding requirements greatly differ depending on the operator’s involvement and the machine’s physical characteristics.
There are five main categorizations of machine guarding methods: guards, devices, by location or distance, ejection and feeding methods, and miscellaneous aids.
Understand Your Machine’s Safeguarding Needs Better With the Help of RPF Environmental’s Expert Technicians
Improperly installed machine safeguards can create additional hazards and may fail in protecting your workers. RPF Environmental’s expert technicians offer machine guarding instructions and evaluations to help you operate your business safely. We have helped numerous customers in the New England area and across the country.
Contact us for more details!
