MACHINE GUARDING GUIDELINES

What is a machine?

BS EN 292 Safeguarding of Machinery defines a machine as ‘an apparatus for applying power, having fixed and moving parts, each with definite functions’. Fundamentally, a machine has:

Operational parts, which perform the primary output function of that machine, such as drilling a hole or pressing sheet metal to a particular shape; and

Non-operational parts, which provide the power or motion to the operational parts, such as the drives to motors.

Operational or functional parts of a machine basically include a ‘prime mover’ and various forms of transmission machinery.

Prime mover means any engine, motor or other appliance which provides mechanical energy derived from steam, water, wind, electricity, the combustion of fuel or other source.

Transmission machinery means every shaft, wheel, pulley, drum, system of fast and loose pulleys, coupling, clutch, driving belt or other devices by which the motion of a prime mover is transmitted to or received by any machine or appliance.

Machinery-related injuries

BS EN 292 outlines the principal causes of machinery-related injuries thus: Coming into contact with machinery, or being trapped between the machinery and any material in or at the machinery or any fixed structure;

·        Being struck by, or becoming entangled in motion in the machinery;

·        Being struck by parts of the machinery ejected from it;

·        Being struck by material ejected from the machinery.

·        The majority of machinery-related hazards are associated with the design features of machinery. These hazards can be classified thus:

Traps. Traps may take three forms:

 Reciprocating traps. This type of trap is featured in the horizontal or vertical movement of machinery, such as power presses and machines incorporating rams, such as compacting machinery. At the point where the injury occurs, the limb is stationary.

Shearing traps. This form of trap involves a guillotine motion where a moving part of the machine traverses a fixed part, or where two moving parts traverse each other, as with a pair of scissors or shears. Various forms of metal cutting machinery incorporate this form of trap.

In-running nips. Nips are created for instance, where a moving belt meets a roller, where a moving belt meets a pulley, and where two moving rollers, drums or toothed wheels meet

Entanglement. Hair, clothing, such as sleeves, and limbs can become entangled in rotating shafts, drills or the chucks to drilling machinery

Ejection. Metal particles from items being machined and the actual parts of a machine may be ejected from a machine. Grinders, for instance, can emit metal particles and grindstone particles. In some cases, a grinding wheel, or abrasive wheel, may burst. Drilling machines may emit part of a broken drill after breakage of the drill.

Contact. Hand or body contact with certain parts of machinery can result in injury, for instance direct burns from hot surfaces, friction burns from moving belts and grinding wheels, and hand injuries from projecting metal fasteners on moving belts.

Events leading to injury

·        Common examples of events leading to machinery-related injury include:

·        Unexpected start-up or movement of machinery;

·        A person reaching into a feed device; Uncovenanted stroke by a machine; and Actual machine failure.

 Machine Guarding Plan

Tips and Considerations

Applicability. This Plan covers  OSHA’s rule for general requirements for machine guarding (29 CFR 1910.212 to 1910.219) in general industry workplaces.

The following rules cover machine guarding requirements for specific machines not covered in this Plan:

• 262, Textiles. Paragraph (c)(3) [reserved] contains a short statement on machine guarding requirements and a reference to 29 CFR 1910.219.
• 263, Bakery equipment. Paragraph (c) addresses general requirements for machine guarding.
• 268, Telecommunications. Paragraph (b)(1)(v) addresses some general requirements for machine guarding.

Voluntary industry standards. Following are industry and voluntary standards for machine guarding:

• ANSI B11.1-2001 Safety Requirements for Mechanical Power Presses
• ANSI B11.2-1995 (R05) Hydraulic Power Presses - Safety Requirements for Construction, Care, and Use
• ANSI B11. 3-2002 Safety Requirements for Power Press Brakes
• ANSI B11.4-2003 Safety Requirements for Shears
• ANSI B11.5-1988 (R05) Ironworkers - Safety Requirements for Construction, Care, and Use
• ANSI B11.6-2001 Safety Requirements for Manual Turning Machines with or without Automatic Control
• ANSI B11.7-1995 (R05) Cold Headers & Cold Formers - Safety Requirements for Construction, Care, and Use
• ANSI B11.8-2001 Safety Requirements for Manual Milling, Drilling, & Boring Machines with or without Automatic Control
• ANSI B11.9-1975 (R05) Safety Requirements for the Construction, Care, and Use of Grinding Machines
• ANSI B11.10-2003 Safety Requirements for Metal Sawing Machines
• ANSI B11.11-2001 Safety Requirements for Gear and Spline Cutting Machines
• ANSI B11.12-2005 Safety Requirements for Roll Forming & Roll Bending Machines
• ANSI B11.13-1992 (R98) Single and Multiple-Spindle Automatic Bar and Chucking Machines - Safety Requirements for the Construction, Care, and Use
• ANSI B11.14-1996 Coil Slitting Machines - Safety Requirements for the Construction, Care, and Use
• ANSI B11.15-2001 Safety Requirements for Pipe, Tube and Shape Bending Machines
• ANSI B11.16-2003 (MPIF #47) Safety Requirements for Powder/Metal Compacting Presses
• ANSI B11.17-2005 Safety Requirements for Horizontal Hydraulic Extrusion Presses
• ANSI B11.18-1997 Safety Requirements for the Machinery Systems for
  Processing or Slitting or Non-Coiled Metal Strip, Sheet or Plate
• ANSI B11.19-2003 Performance Criteria for Safeguarding
• ANSI B11.20-2004 Safety Requirements for Integrated Manufacturing Systems
• ANSI B11.21-1997 Safety Requirements for Machine Tools Using Lasers for Processing Materials
• ANSI B11.22-2002 Safety Requirements for Turning Center and Automatic Numerically Controlled Turning Machines
• ANSI B11.23-2002 Safety Requirements for Machining Centers and Automatic Numerically Controlled Milling, Drilling and Boring Machines
• ANSI B11.24-2002 Safety Requirements for Transfer Machines
• ANSI B11.TR1-2004 Ergonomic Guidelines for the Design, Installation and Use of Machine Tools
• ANSI B11.TR2-1997 Mist Control Considerations for the Design,
  Installation and Use of Machine Tools Using Metalworking Fluids
• ANSI B11.TR3-2000 Risk Assessment and Risk Reduction - A Guideline to Estimate, Evaluate and Reduce Risks Associated with Machine Tools
• ANSI B11.TR4-2004 Selection of Programmable Electronic Systems (PES/PLC) for Machine Tools
• ANSI B11.TR5-200X (not an approved document; in development)
  Sound Level Measurement Guidelines
• ANSI B11.TR6-200X (not an approved document; in development)
  Control Reliable Circuits and Servo Drive Technology

Review and incorporate state regulatory requirements. This plan is based on federal requirements and/or best practices. Some states have laws and regulations that are stricter than federal requirements and may affect how you customize this plan.

Machine Guarding Plan

Authority and Scope

Regulation: 29 CFR 1910.212, General Requirements for Machinery and Machine Guarding [Replace with the state regulation if applicable.]

Scope: All employees and contractors of [name] who operate or service machines and machine tools. The use of powered and manpowered portable hand-held tools (such as sanders, drills, sawzalls®, staple guns, impact wrenches, powder actuated tools, screwdrivers, wrenches, files, hammers, scissors, etc.) is not addressed in this Plan.

Policy Statement

It is the policy of [name] to protect its employees from injury. Employees will be protected from hazards related to machines and  equipment through engineering controls, machine safeguards, communication of hazards and solutions, personal protective equipment, and training.

Plan Administration

Table [number] provides the employees with contact information for the administration of the electrical safety program.

Program Contact Information

[Modify the table and job descriptions that follow the table as applicable to your organization.]

Function	Name, job title, or department	Contact Information
Plan Administrator	[name]	Work phone: Cell phone:
Safety Committee Chairperson		Work phone: Cell phone:
[Other]		Work phone: Cell phone:

Plan Administrator. The Electrical Plan Administrator will provide safe work procedures and permits for electrical work as required, and provide and implement other critical procedures such as lockout/tagout, testing, and safety-related work practices as required by regulation. Specifically, the Administrator will:

• Ensure that employees who work or who may potentially work near exposed energized parts are trained and qualified.
• Ensure that approved, maintained, and tested personal protective equipment (PPE) and other electrical safety equipment are provided, available, and used properly.
• Establish, implement, and maintain procedures that will ensure electrical safe work practices.
• Establish and maintain records as required.
• Develop and oversee training courses, and assist other managers with their employee training responsibilities.

Supervisor(s). Supervisors will:

• Complete applicable training.
• Ensure that employees follow all machine-guarding safety practices and procedures.
• Ensure that employees receive required training at the prescribed times.

Safety Committee Chairperson. The Safety Committee Chairperson and other Safety Committee members will assist the Plan Administrator with interpreting safety policies and regulations and communicating safety solutions to employees.

Employees. All employees, including employees of contractors working at work sites, are responsible to comply with all safety rules and policies as directed by management that apply to their own actions and conduct, including immediate reporting to management of unsafe and unhealthful conditions. 

Plan Review and Update

This Plan will be reviewed and updated periodically and whenever:

• New types of machines, equipment, or guards are introduced into the workplace
• Evaluations of workplace hazards, injuries, and near-misses demonstrate that the current plan is outdated or not effective.
• When regulatory or national consensus standards change that require this Plan to be updated.

Definitions

Authorized person—One to whom the authority and responsibility to perform a specific assignment has been given by the employer.

Flanges—Collars, discs, or plates between which wheels are mounted and are referred to as adaptor, sleeve, or back-up type.

Device—A press control or attachment that:

• Restrains the operator from inadvertently reaching into the point of operation;
• Prevents normal press operation if the operator’s hands are inadvertently within the point of operation;
• Automatically withdraws the operator’s hands if the operator’s hands are inadvertently within the point of operation as the dies close; or
• Prevents the initiation of a stroke or stops the stroke in progress when there is an intrusion through the sensing field by any part of the operator’s body or by any other object.

Feed—The process of placing or removing material within or from the point of operation.

Guard—A barrier that prevents entry of the operator’s hands or fingers into the point of operation, pinch point, or moving parts of a machine or auxiliary equipment, and also protects the worker from flying parts and sparks.

Nip/pinch point—Any point other than the point of operation at which it is possible for a part of the body to be caught between the moving parts of the machine or auxiliary equipment, or between moving and stationary parts of a machine or auxiliary equipment, or between the material and moving part or parts of the machine or auxiliary equipment.

Point of operation—The area on a machine where work is actually performed on the material being processed.

Safety system—The integrated total system, including the pertinent elements of the machine, the controls, the safeguarding, and any required supplemental safeguarding, and their interfaces with the operator, and the environment, designed, constructed, and arranged to operate together as a unit, such that a single failure or single operating error will not cause injury to personnel due to point of operation hazards.

Stock—The material or item being processed or worked on at the point of operation.

Hazard Assessment

[Name] has conducted a job hazard analysis (JHA) of all machines and equipment for potential to cause injury to personnel. See Attachment [number] for a copy of the Job Hazard Analysis Worksheet, and Attachment [number] for a copy of the Hazard Assessment Survey.

On the basis of the assessment, the following machines and equipment must be safeguarded:

[List the machines at your facility here or as an attachment.]

• guillotine cutters, shears, alligator shears, power presses, milling machines, power saws, jointers, portable power tools, forming rolls, and calendars

If the results of the JHA show the machine or equipment to pose no hazard to the employee, changes to the equipment may not be necessary.

Accident Investigations

All incidents that result in injury to workers, as well as near misses, regardless of their nature, will be reported and investigated. Investigations will be conducted by [name] or other authorized person as soon after an incident as possible to identify the cause and means of prevention to eliminate the risk of reoccurrence.

In the event of an incident that results in serious injury, this Plan will be reevaluated by [name] to determine if additional practices, procedures, or training is necessary to prevent similar future incidents.

New Machines or Equipment

Before any new machines or related equipment is purchased, [name(s)] will review all specifications to ensure that the guards are suitable and do not interfere with the work and that there are no unguarded moving parts. They will also determine whether the equipment meets all regulatory requirements.

Hazard Control

Machine hazards will be eliminated or controlled according to the following hierarchy:

1.     Eliminate the hazard by design (engineering controls)

2.     Control the hazard by safeguarding (guards or devices)

3.     Safe work practices

4.     Posting of warning signs and notices

5.     Personal protective equipment

6.     Training

Engineering Controls

Machines designed for a fixed location will be securely anchored to prevent walking or moving.

Two types of engineering controls are used at this facility to eliminate certain point-of-operation machine hazards:

• Keeping your distance
• Feeding and ejection methods

Keeping Your Distance

[Describe the controls for keeping distance between the machine operator and machine, if applicable. Otherwise, delete this subsection.]

Feeding and Ejection

Stock feeding and ejection methods do not require the operator to place his or her hands in the danger area of a machine. The following feeding and ejection methods have been installed at this facility:

[Modify and describe as applicable.]

• Automatic feed
• Semiautomatic feed
• Automatic ejection
• Semiautomatic ejection
• Robots

Safeguards

In addition to engineering controls, three types of safeguards used at this facility are:

[Revise the list as applicable.]

• Guards
• Devices
• Miscellaneous aids

Guards

Machine guards must prevent hands, arms, and any other part of a worker’s body from making contact with dangerous moving parts. All machines covered by this Plan will be provided with the proper guards and installed according to manufacturer’s recommendations and as required by applicable safety rules. Safety input and approval from [name] must be obtained when manufacturer recommendations for guarding a specific machine are not available or cannot be implemented.

See Attachment [number] for a list of machines that require guards and the types of guard(s) required for each machine.

Guards will be affixed to each machine where possible and secured elsewhere if for any reason attachment to the machine is not possible. Each guard will be installed in a way that will prevent it from acting as an accident hazard in itself.

Point of operation. All nip point or points of operation on machines that expose employees to injury will be guarded.  If it is not possible or impractical to install or provide guards at the point of operation, machine operators and setup and maintenance personnel will use devices, safe work practices, personal protective equipment, and special tools adequate to ensure that the work can be performed safely.

Note: Special tools will not be in lieu of other guarding, but can only be used to supplement protection provided.

Moving parts. Guards will be installed on all belts, chains, gears, flywheels, shafts, pulleys, or other reciprocating, rotating, or moving parts exposed to contact by employees. Guards must be attached to machines where possible or secured elsewhere if the guard(s) cannot be attached directly to the machine. Guards will be installed so that they do not create a hazard; for example, so that no objects such as small tools can fall into moving parts.

Fans. If blade tips of a fan are installed less than seven feet above the floor or working level, guard the blades with a guard having openings no larger than one-half inch wide.

Revolving barrels, containers, and drums.  Revolving barrels, containers, and drums must be guarded by an enclosure interlocked with the drive mechanism, so the barrel, gun, or container cannot revolve unless the guard enclosure is in place.

Types of guards used at this facility include:

[List all the types of guards used, if possible.]

• Barrier guards
• Two-hand tripping devices
• Electronic safety devices

Guard modifications. If a machine needs to be modified or retrofitted with new guards, the manufacturer will be contacted for guidance on correct procedures. If the modifications are initiated and performed in-house, [name(s)] will ensure the changes meet regulatory requirements before approving the work.

Devices

Safeguarding devices are used at this facility to [Delete any of the following safety measures that do not apply to your machines: stop the machine if a hand or any part of the body is inadvertently placed in the danger area; restrain or withdraw the operator’s hands from the danger area during operation; require the operator to use both hands on machine controls, which keeps both hands and body out of danger; or provide a barrier which is synchronized with the operating cycle of the machine in order to prevent entry to the danger area during the hazardous part of the cycle.]. 

General Safe Work Practices

Following are general safe work practices the machine operators and setup and maintenance personnel will implement:

• Guards will not be removed unless the machine is locked and tagged out.
• Notify a supervisor immediately when any unguarded moving parts or dangerous points of operation are observed. Stop work and shut down the machine until the condition is corrected.
• Operate equipment only when the proper machine guards are in place.
• Do not use unauthorized or damaged guards.
• Never leave machines unattended with parts still moving. Even after the machine is turned off, some parts may still be moving.
• Never remove or bypass any machine guards.
• Maintain good housekeeping practices by keeping your work area free of debris or other items that can get caught in machinery.
• Operate machines only when all guards are in place and properly attached according to the manufacturer’s recommendations, and functioning properly.
• Perform maintenance or repair work on guarded machines only when the machine is properly shut down and all hazardous conditions are eliminated.
• Use designated special feeding tools (i.e., push sticks) to keep hands out of danger zones.
• Never use hand tools as a substitute for required guards; all required guards must be in place before operating a machine.
• Wear proper eye and face protection while operating the machines.
• Hair covering or protection will be worn in all manufacturing areas.
• If a machine guard is damaged, bypassed, or missing, shut down the machine until the problem is corrected.
• Never wear loose clothing or jewelry while operating the machines.

Prohibited Clothing and Jewelry

Machine operators and setup and maintenance personnel are prohibited from wearing the following clothing and jewelry near machines or related equipment:

• Necklaces or chains
• Bracelets
• Neckties
• [other]

Machine and Equipment Maintenance

Maintenance or repair work on guarded machines will be performed only when the machine is properly shut down and all hazardous conditions are eliminated.

[Name] will initiate a program of periodic and regular inspections and maintenance of equipment to ensure that machines, parts, and auxiliary equipment are in a safe operating condition and necessary safeguards are present. Records of these inspections will be maintained and made available for inspection upon request.

When maintenance requires entry of any body part into a danger zone within the equipment, or unexpected startup or energizing of the machine could cause injury, maintenance personnel will first isolate the hazardous energy according to lockout/tagout procedures. See Attachment [number] for a copy of the facility Lockout/Tagout Plan.

Signs and Notices

All employees will follow posted safety instructions, prohibitions, warnings, and notices in work areas.

Personal Protective Equipment

Eye, face, and head protection will be provided to each employee when exposed to eye, face, or other hazards from flying particles.

Miscellaneous Aids

Awareness Barrier

An awareness barrier serves as a reminder to a person that he or she is approaching the danger area. Although the barrier does not physically prevent a person from entering the danger area, it calls attention to it. Awareness barriers have been installed on the following machines:

[List machines or equipment.]

Special Tools

Machine operators may use special hand tools to place or remove stock, particularly from or into the point of operation of a machine. Special tools are:

[List the special tools, such as a push stick or block.]

Training

All machine or equipment operators and setup and maintenance personnel will be trained in the proper operation, safety procedures, hazard recognition, and emergency shutdown procedures for each machine or piece of equipment they use or maintain before beginning work on such machinery or equipment. Only trained personnel or those undergoing supervised on-the-job training will be allowed to operate or maintain machinery or equipment.

At a minimum, the training program will include:

• A description and identification of the hazards associated with particular machines
• The safeguards themselves, how they provide protection, and the hazards for which they are intended to correct or eliminate
• How to use the safeguards and why
• How and under what circumstances safeguards can be removed, and by whom (in most cases, repair or maintenance personnel only)
• When a lockout/tagout program is required
• What to do (e.g., contact the supervisor) if a safeguard is damaged, missing, or unable to provide adequate protection.

Additionally, employees will demonstrate that they know and understand the features of the equipment, all applicable safety rules, and are skilled in operating the equipment or performing machine setup or maintenance tasks.

Certification of Training

[Name] will certify that employees have been trained by preparing a certification record which includes the identity of the person trained, the signature of the employer or the person who conducted the training, and the date the training was completed. The certification will be maintained on file for the duration of the employee’s employment.

Refresher Training

Machine operators and maintenance or setup personnel will be provided refresher training when:

• Any new or altered safeguards are put into service
• Workers are assigned to a new machine or operation

Recordkeeping

[Name] will keep all specifications and designs for each machine in their files.

All other records, reports, schedules, and attachments related to this Plan will be kept with [name or department] for [duration].

Machine guarding is required as a basic need as well as statutory requirement.

Basic Need and Importance:

The basic need of machine guarding is to protect against contact with the dangerous and moving parts of a machine, work in process and failure due to mechanical, electrical, chemical or

human causes. The guards remove workers’ fear and thereby increase their morale and the production. They allow the operation at higher speeds and compensate the expenditure on

guarding. Where danger exists from machinery, safe working practice alone is insufficient and cannot be relied on from safety point of view. Guards are essential as an engineering and built-in control to prevent accident when other precautions fail.

It is obvious that when cutting edges of sharp tools, rotating and projecting parts, point of operation or contact point of die and punch, nip (contact) points of pulley – belts or gears,

rollers, calendar rolls, traversing tools or bed etc. are unguarded and workers are exposed to such openly moving i.e. unguarded parts, their risk of accident is highest. Long sleeves (shirt), sadis, chain, i.e. muffler, shawl etc can trap or

entangle into unguarded rotating parts and serious or fatal accidents are possible. Many such accidents have happened also. Therefore, basic need of machine guarding must first be

understood.

Mainly machine guarding is of two types:

(1) Guarding for points of operation i.e. guarding for cutting edges, tool points, press or shear points, nip or running contact points, feed points etc., 

(2) Guarding for Power

Transmission Machinery i.e. gears, pulley-belts, couplings, clutches, brakes, cams, shafts, rolls, rods that transmit energy and motion from the source of power (prime mover) to the point of operation.

PRINCIPLES OF MACHINE GUARDING

Definitions:

1. Point of operation: That area on a machine where material is positioned for processing by the machine and where work is actually being performed on the material.

2. Zero Mechanical State (ZMS): The mechanical state of a machine in which every power source that can produce a

machine member movement has been shut/locked off. This means de-energized, de-pressurized and neutralized condition of the machine or equipment which provides maximum protection against unexpected mechanical movement.

3. Power off: The state in which power

(electric, pneumatic, hydraulic, atomic etc.)

cannot flow to the machine is considered a power-off stage.

4. Power-locked off: The state in which the device that turns power off is locked in the off position with the padlock of every

individual who is working on the machine.

5. Guarding: Any means of effectively preventing personnel from coming incontact with the moving parts of machinery or equipment which could cause physical harm to the personnel. In case of a powerpress, a cover on point of operation (die and punch) is called ‘guard’ while those on other danger zones are called ‘enclosure’ or ‘safeguard’. Safety by Guarding is most important as other methods are not always possible. Depending upon the dangerous part, its size, position, speed etc., a guard should be selected. Generally the parts to be guarded fall within three categories :

1. The prime mover.

2. Transmission parts from the prime mover to the machine and the transmission parts in the machine itself.

It is desirable to minimize them and enclose completely.

3. Operating parts of a machine, of which

the points of dangerous operation need

effective guarding.

6. A machine guard means any enclosure, barrier or device constructed to prevent a person or his clothing coming into contact with dangerous parts of the machine. The

point of operation is that part of working machine at which cutting, shaping, forming or any other necessary operation is

accomplished. A guard for that part is known as the point of operation guard.

7. Enclosures: Guarding by fixed physical barriers that are mounted on or around a machine to prevent access to the moving parts.

8. Fencing: Guarding by means of a locked fence or rail enclosure which restricts access to the machine except by authorized personnel. Enclosures must be a minimum

1 m (42 in) away from the dangerous part of the machine.

9. Safety by Position or Location: It is a guarding as a result of the physical inaccessibility of a particular hazard under

normal operating conditions or use. Words “Safe by location” or “Safe by position” are used to denote safety by distance.

10. Ingoing (in-running) Nips: A hazard area created by two or more mechanical components rotating in opposite directions

in the same plane and in close conjunction or interaction e.g. calendar rolls, in running rolls of textile or paper machines.

11. Safety by Construction: It indicates parts so constructed as to cause no hazard, viz. shaft, sliding and link mechanism so located or with slow speed that their contact is not dangerous. Built-in-safety- is the similar word for designing and constructing new machinery in such a way to make the

dangerous parts safe by deep housing or position etc.

Elimination of Hazard :

Hazards from machinery are generally of following types :

Crushing, shearing, cutting or severing, entanglement, drawing-in or trapping, impact, stabbing or puncture, friction or abrasion, ejection of material from the machine, contact

with moving part, hot surface or sharp edge, free fall of any material, tool or equipment and high-pressure fluid ejection.

The basic steps to prevent accidents are :

1. Eliminate the hazard from the machine, method, material, structure etc.

2. Control the hazard by enclosing or guarding it at its source.

3. Train personnel to know that hazard and to follow the safe job method to avoid it and

4. Use personnel protective equipment necessary.

Thus machine guarding is one of the basic step to eliminate hazard. Actually the machine should be so designed and constructed that all safety points are incorporated by built-in safety principle and need of extra guards should be minimum. A machine safety checklist given by the NSC, USA is worth mentioning. It suggests:

1. Design the machine so that it is impossible for an operator to get at the point of operation or any other hazard point while

the machine is working.

2. Design the machine so that corners and edges are rounded.

3. Locate machine controls so that the operator will not be in the vicinity of the point of operation while actuating the controls.

4. Place the control so that the operator will not have to reach too far or move his body off balance in order to operate the machine.

5. Build power transmission and drive mechanisms as integral parts of the machine.

6. Build overload devices into the machine.

7. Design the machine for single-point lubrication.

8. Design mechanical, instead of manual holding devices.

9. Design a mechanical device for feeding and ejecting parts so as to eliminate the use of hands for such operations.

10. Minimize motor drift-time.

11. Provide fail-safe interlocks so that the machine cannot be started when it is being loaded or unloaded or being worked on.

12. Provide a grounding system for all electrical equipment.

13. Provide standard access platform and ladders for inspection and maintenance of equipment.

14. Design component parts of equipment for easy and safe removal and replacement to facilitate maintenance.

15. Reduce sources of excessive noise, vibration,

heat etc. Such built-in-care in construction principles of a machine or equipment should also ensure that it will cause no harm to the environment, no discomfort to the operator, no

operational contingencies, no contact with overheated or chilled surfaces, no electrical accident and no access to the danger zone.

Groups of Dangerous Parts:

1. According to Motions :

Dangerous parts to be guarded according to their motions are generally classified as follows :

Group-1. Rotary Motions : 

(1) Rotating parts alone viz. shafts, coupling, spindles, projections on moving parts, fly-wheel, saw, gear, knife, cutting tool etc. 

(2) In-running nips subdivided as

 (a) Between parts rotating in opposite direction - gears, rolls etc.

 (b) Between rotating and tangential moving parts - conveyors, belt drives rack and pinion etc.

(c) Between rotating and fixed parts – grinding wheel, paper machine felt or roll, drums, cylinders, worms, spirals etc.

Group-2. Reciprocating Sliding Motions :

(1) Reciprocating sliding motions and fixed parts

 (a) Approach type - danger of crushing viz. slides (rams) on power presses and forging hammers, pistons, cross rod of a steam engine and riveting machines 

(b) Passing types - danger of shearing, viz. planning machine, shaper, spot welder clamping fixtures, guillotine and the shear, power press etc.

 (2) Single sliding motion - abrasive or sharp nature of objects such as saws or crocodile clips on belts.

Group-3. Rotating/Sliding Motion : 

A cam gear having sliding and turning movement etc. falls within this group.

Group-4. Oscillating Motions:

 Trapping points between two moving parts or between a moving part and a fixed object viz. a pendulum, crankshaft, closing platens etc.

 According to H.A. Hepburn 25 groups of intrinsically dangerous parts of machinery as classified by H.A. Hepburn are

as follows :

 Single Revolving Units - Risk of entanglement

1. Revolving open arm pulleys and other discontinuous rotating parts – Fan blades, spur gear wheels etc.

2. Revolving worms or spirals in casing - Meat minces, rubber extruders, spiral conveyors.

3. Projections on revolving parts – Key heads, set screws, cotter pins, complying belts etc.

4. Revolving shafts, spindles, mandrels and bars - drills, reamers, boring bar, stock bar, milling etc.

5. Revolving high speed cages in casings - Hydro-extractors, centrifuge.

6. Revolving or oscillating mixer arms in casings - Dough mixture, rubber solution mixture.

7. Revolving drums and cylinders - uncased - Rumbles, shaking barrels, rag digesters etc.

8. Revolving cutting tools - Circular saws, milling cutters, shears, routers, chain mortises.

9. Abrasive wheels - Grinding wheels etc. In-running Parts - Risk of nipping and tearing

10. In running nips of the belt and pulley type - Pulley - belt, chain and sprocket gear, conveyor belt etc.

11. Revolving beaters, spiked cylinders and drums - Scutchers, cotton opener, and laundry washers.

12. In running nips between pairs of revolving parts - Gear wheels, friction wheels, calendar bowls, mangle rolls etc.

13. Nips between gears and rack strips. Reciprocating Tools or Parts - Risk of cutting or crushing

14. Moving balance weights and dead weights - Hydraulic accumulators, balance weight on slotting machine etc.

15. Reciprocating knives and saws - Guillotines for metal, rubber and paper cutting, trimmers, perforators etc.

16. Nips between reciprocating and fixed parts other than tools and dies – Sliding table and fixture, shaping machine and fixture.

17. Closing nips between platen motions - Letter press platen printing machine, power presses.

18. Reciprocating tools and dies – Power presses, drop stamps, relief stamps, bending press, revolution press.

19. Nips between revolving control handles and fixed part - Traverse gear handles of lathes, milling machine etc.

20. Nips between revolving wheels or cylinders in pans or on tables – Sand mixtures, edge runners, crushing mill, mortar mill etc.

21. Nips between fixed parts and unidirectional moving parts – Buckets or hoppers or conveyors against tipping-bars etc.

22. Nips between connecting rods or links and rotating wheels, cranks or disc - Flat bed printing machine, jacquard loom, automatic looms.

23. Pawl and notched wheel devices for intermittent feed motions - Planer tool feed motion, power press dial feed table etc. Running Edges - Risk of cutting

24. Cutting edges of endless band cutting machines - Band saws, band knives.

25. Projecting belt fasteners and fast running belts - Bolt and nut fasteners, wire pin fasteners, centrifuge belt etc.