Types of Machine Safeguarding: Important Items to Know

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.

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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 operateTwo-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 clutchesGate&#; 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 dangerReciprocating 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 PointsHazards 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 injuriesPunching Actions&#; Actions that involve applying power to a ram/slide for stamping, drawing, or blanking stocksBending Actions&#; Similar to punching actions but they are for stamping or drawing stocks onlyShearing&#; 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

What are the two types of primary safeguarding methods by OSHA?

The primary methods are guards and devices which are used to greatly reduce or prevent amputation injuries. 

What are the three basic areas of a machine that require safeguarding?

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.

How many methods of machine guarding are there?

There are five main categorizations of machine guarding methods: guards, devices, by location or distance, ejection and feeding methods, and miscellaneous aids.

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What are Machine Guards and Safeguarding?

Safeguarding and machine guards are a part of the process of preventing contact between moving mechanical parts and skin or clothing. It can also include controlling emitted particles or sparks. 

Some normal applications include gates or panels which cover the moving parts. Using guard enclosures to make sure the machine is not operating without the right conditions is another good way to safeguard machines. There are plenty of size and mobility options depending on the needs of the machine (EHS).

Why Are They Important?

The purpose of machine guarding is to protect the machine operators and other employees in the work area from hazards created during the machine&#;s normal rotation. Because of this, it is a crucial component of safety across all industries. 

Safeguarding is required to maintain a safe work environment. According to OSHA, machine guarding is the first line of defense to protect employees from machine-related injury.

Complying With OSHA Requirements

There are many steps that must be taken in order to adhere to OSHA requirements. The first one is to identify all of the potential hazards in the workplace. Once the hazardous areas are identified, safeguarding the machinery will come afterward and with ease. 

Once the hazards are identified, machine safeguards must follow six standards in order to be compliant with OSHA&#;s requirements:

1. Prevent contact &#; The safeguard must prevent clothing and other body parts from coming into contact with the machine.
2. Stay secure &#; Machine guards should be made of high-quality materials and secured to the machine. Employees should not easily be able to tamper with or remove the machine guard.
3. Stop falling objects &#; The safeguard should ensure that no objects can fall into or disturb the moving parts.
4. Allow safe maintenance &#; Employees should ideally be able to lubricate and inspect the machine without going beyond the safeguard.
5. Create no interference &#; Any safeguard that prevents employees from doing their job quickly and efficiently may be ignored depending on the operation and type of machine. This can quickly lead to injury.
6. Introduce no new hazards &#; Safeguards should not impede or interrupt robotic machinery. They must not have any burrs, jagged edges, or rough materials, as this defeats their purpose. 

Moving Mechanical Parts

A moving mechanical part is hazardous regardless of any other factors. Employees that work around moving machines are at risk of getting injured at any moment. There are many different types of hazardous motions that have unique points at which they could make contact with clothing or skin. Some of these basic hazardous motions are:

• Rotating
• Punching
• Shearing
• Bending
• Reciprocating
• Transversing actions
• Cutting

Each piece of machinery has its own unique mechanical and non-mechanical hazards. Machines can cause a variety of injuries ranging from minor abrasions, burns, or cuts to severe injuries such as fractures, lacerations, crushing injuries, or even loss of limb. Because of the risks, each machine must have adequate safeguards to protect operators and any employees that work around the machine. 

Different Types of Machine Guards

There are many different types of machine guards. According to OSHA, the most common types of guards can be categorized into one of four general types of machine guards:

1. Fixed
2. Interlocked
3. Adjustable
4. Self-adjusting 

Each type of machine guard has their own advantages and disadvantages. We will go over and discuss what these guards are throughout the next few sections. 

Fixed

A fixed guard is a permanent part of the machine. It provides a barrier and does not depend on the moving parts to function. It should be constructed of any material that is substantial enough to withstand whatever impact it may receive and be able to endure prolonged use. This type of machine guard is commonly preferred over other types because of its simplicity. 

There are some great advantages that go along with fixed machines. For example, they:

• Can be constructed to suit many specific applications
• Can provide maximum protection
• Usually requires a minimal amount of maintenance
• Can be suitable for high production, repetitive operations

There are a few limitations as well. Fixed guards can interfere with operator visibility. When a fixed guard does need to be repaired or adjusted, it has to be completely removed from the machine until it is fixed. Because of this, a temporary means of protection will need to be used while it is being repaired.

Interlocked

When this type of guard is opened or removed, the tripping mechanism and power automatically shut off and disengage, which stops the moving machine parts. The machine cannot cycle or be started again until the guard has been properly put back in place. An interlocked machine guard could use electrical, mechanical, hydraulic power, or any combination of these.

Interlocked guards benefit employees by providing maximum protection and allowing access to the machine for removing jams without the time-consuming removal of the fixed guards.

But these types of guards also require careful adjustment and maintenance, which takes up a lot of time. Plus, interlocked guards can be easily disengaged, meaning a bump in the machine could cause a jam. This hurts both the machine and employee productivity. 

Adjustable

Adjustable guards are useful because they allow flexibility in the accommodation of various sizes of stock. The term &#;stock&#; refers to raw material from which something is manufactured. Adjustable guards provide a barrier that can be adjusted to facilitate different production operations. An advantage of an adjustable safeguard is that it can be constructed to suit many specific applications. 

Unfortunately, this type of guard may have more disadvantages than advantages. Here are a few examples of the limitations this type of guard is associated with:

• Hands could enter the danger area, meaning protection may not be complete at all times
• It may require frequent maintenance and adjustment
• The guard might be made ineffective by the machine operator
• It might interfere with visibility

Self-adjusting

The openings of these barriers are determined by the movement of stock. As the operator moves the stock into the danger area, the guard is pushed away, providing an opening that is only large enough to admit the stock. 

After the stock is removed, the guard returns to the rest position. The guard protects the operator by placing a barrier between them and the danger area. These types of guards could be constructed of substantial material. Self-adjusting guards offer different degrees of protection. (OSHA).

Some limitations of self-adjusting guards include not always providing maximum protection, interfering with operators&#; visibility, and requiring a lot of maintenance and adjustment. 

Safeguard Devices

Safeguard devices work towards eliminating hazards for machine operators and employees. These devices have many different functions, all of which protect employees. Some examples of these functions would be:

• Stopping the machine if a hand or part of the body is inadvertently placed in the danger area
• Restraining or withdrawing the operator&#;s hands from the danger area during operation
• Requiring the operator to use both hands on machine controls
• Providing a barrier that is synchronized with the operating cycle of the machine

There are six commonly used safeguard devices that all work towards protecting employees from getting hurt. These six devices will be discussed in the next couple of sections.

Six Common Types of Devices

1. Presence-Sensing Devices &#; These devices use a system of light or radiofrequency sources and controls which can interrupt the machine&#;s operating cycle. 
2. Pullback Devices &#; A pullback device uses a series of cables attached to the operator&#;s hands, wrists, or arms. 
3. Restraint Devices &#; The restraint device uses cables or straps that are attached to the operator&#;s hands at a fixed point. 
4. Safety Trip Controls &#; Safety trip controls provide a quick means for deactivating the machine in an emergency situation. A pressure-sensitive body bar, when depressed, will deactivate the machine
5. Two-Hand Control Devices &#; The two-hand control device requires constant concurrent pressure by the operator to activate the machine
6. Two-Hand Trip Devices &#; The two-hand trip device requires concurrent application of both the operator&#;s control buttons to activate the machine cycle, after which the hands are free.

Always be Armed With Knowledge

It is important for employees to be able to work safely around machines and understand how to utilize machine guards and safeguard devices. It is the employer&#;s responsibility to provide safety training for them. An online safety course provider such as Safety Provisions, Inc. will be able to help you with all required training your employees need.

This safety training should teach OSHA&#;s requirements for machine guards and safeguard devices. It should also teach employees how to inspect their equipment and who to report to if the equipment needs maintenance. Knowing how to utilize the safety tools they are provided with will be workers&#; best chance at staying safe in their workplace.

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