Mechanical hazard control

Mechanical hazard control
Ahsanullah Soomro
09/20/14 Engr. Ahsanullah Soomro 1

General requirements for work
equipment
• Any equipment used by an employee at work is
generally covered by the term ‘work equipment’.
• The scope is extremely wide and includes hand tools,
power tools, ladders, photocopiers, laboratory
apparatus, lifting equipment, fork-lift trucks, and
motor vehicles etc.
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General requirements for work
equipment
• Employers must ensure that work equipment is
suitable, maintained, inspected if necessary,
provided with adequate information and instruction
and only used by people who have received
sufficient training
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Suitability of work equipment
and CE (Conformité Européene) marking
• When work equipment is provided it has to conform
to standards which cover its supply as a new or
second-hand piece of equipment and its use in the
workplace.
• This involves:
– its initial reliability
– the place where it will be used
– the purpose for which it will be used.
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and CE marking
• There are two groups of law that deal with the
provision of work equipment:
• One deals with what manufacturers and suppliers
have to do.
• The CE marking ("Conformite Europeenne") certifies
that a product has met EU health, safety, and
environmental requirements, which ensure
consumer safety.
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and CE marking
• The other deals with what the users of machinery
and other work equipment have to do
• Its primary purpose is to protect people at work.
• Under ‘user’ law employers have to provide safe
equipment of the correct type, ensure that it is
correctly used and maintain it in a safe condition
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and CE marking
• When buying new equipment, the ‘user’ has to check
that the equipment complies with all the ‘supply’ law
that is relevant.
• The user must check that the machine is safe before
it is used.
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Prevention of access to dangerous
parts of machinery
• Employers must to take effective measures to
prevent access to dangerous parts of machinery or
stop their movement before any part of a person
enters a danger zone
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parts of machinery
• The term ‘dangerous part’ has been established in
health and safety law.
• In practice, this means that if a piece of work
equipment could cause injury and if it is being used
in a predictable way, it can be considered a
dangerous part.
• The risk assessment carried out to identify hazards
presented by machinery.
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parts of machinery
• The risk assessment should evaluate the nature of
the injury, its severity and likelihood of occurrence
for each hazard identified
• In most cases the objective of risk reduction
measures is to prevent contact of part of the body or
clothing with any dangerous part of the machine, for
example by providing guards.
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Use and maintenance of equipment
with specific risks
• Some pieces of work equipment involve specific risks
to health and safety where it is not possible to
control adequately the hazards by physical measures
alone, for example the use of a bench-mounted
circular saw or an abrasive wheel
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with specific risks
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with specific risks
• In all cases the hierarchy of controls should be
adopted to reduce the risks by:
– eliminating the risks; or, if this is not possible
– taking physical measures to control the risks such as
guards; but if the risks cannot be adequately controlled
– taking appropriate software measures, such as a safe
system of work.
– Or use PPE
• The hierarchy of control is a sequence of options which offer
you a number of ways to approach the control of hazards.
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with specific risks
• Repairs, modifications, maintenance or servicing is
also restricted to designated persons.
• A designated person may be the operator if he/she
has the necessary skills and has received specific
instruction and training.
• Another person specifically trained to carry out a
particular maintenance task, for example dressing an
abrasive wheel, may not be the operator but may be
designated to do this type of servicing task on a
range of machines.
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with specific risks
• People using and maintaining work equipment,
where there are residual risks that cannot be
sufficiently reduced by physical means, require
enough information, instruction and training to
operate safely.
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Information, instruction and training
• The information and instructions are likely to come
from the manufacturer in the form of operating and
maintenance manuals.
• It is up to the employer to ensure that what is
provided is easily understood, and set out logically
with illustrations and standard symbols where
appropriate
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• The extent of the information and instructions will
depend on the complexity of the equipment and the
specific risks associated with its use. They should
cover:
– all safety and health aspects;
– any limitations on the use of the equipment;
– any foreseeable problems that could occur;
– safe methods to deal with the problems;
– any relevant experience with the equipment that would
reduce the risks or help others to work
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• Everyone who uses and maintains work equipment
needs to be adequately trained.
• The amount of training required will depend on:
– the complexity and level of risk involved in using or
maintaining the equipment;
– the experience and skills of the person doing the work,
whether it is normal use or maintenance.
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• Training needs will be greatest when a person is first
appointed but will also need to be considered:
– when working tasks are changed, particularly if the level of
risk changes;
– if new technology or new equipment is introduced;
– where a system of work changes;
– when legal requirements change;
– periodically to update and refresh people’s knowledge and
skills;
– following an accident.
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• Supervisors and managers also require adequate
training to carry out their function
• The training and supervision of young persons is
particularly important because of their relative
immaturity, unfamiliarity with a working
environment and lack of awareness of existing or
potential risks.
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Maintenance and inspection
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Maintenance
• Work equipment needs to be properly maintained so
that it continues to operate safely
• The amount of maintenance will be required in the
manufacturer’s instructions and will depend on the
amount of use, the working environment and the
type of equipment
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Maintenance
• Maintenance management should focus on those
parts which deteriorate and need to be maintained
to prevent health and safety risks.
• These techniques include the following:
• Preventative planned maintenance
• Condition based maintenance
• Breakdown based maintenance
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Preventative planned maintenance
• This involves replacing parts and making necessary
adjustments normally set by the manufacturer, so
that there are no hazards created by component
deterioration or failure.
• Vehicles are normally maintained on this basis.
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Condition based maintenance
• this involves monitoring the condition of critical parts
and carrying out maintenance whenever necessary
to avoid hazards which could otherwise occur.
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Breakdown based maintenance
• here maintenance is only carried out when faults or
failures have occurred.
• It is essential to ensure that maintenance work can
be carried out safely. This will involve the following:
– competent well-trained maintenance people;
– the equipment being made safe for the maintenance work
to be carried out.
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Breakdown based maintenance
– necessary procedures are required to make and keep the
equipment safe and perform the maintenance tasks.
• This can often involve a formal ‘permit-to-work’ scheme
– correct tools and safety equipment being available to
perform the maintenance work without risks to people.
• For example special lighting or ventilation may be required.
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Inspection
• an inspection is, most generally, an
organized examination or formal evaluation exercise to
ensure continued safe operation
• an official process of checking that things are in the
correct condition or not
• competent person for inspection would normally be an
employee,
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Inspection
• but there might be circumstances
where an outside competent person
would be used.
• The inspection must be done:
– after installation for the first time;
– after assembly at a new site or in a new
location and thereafter;
– at suitable intervals;
– each time special circumstances occur
which could affect safety
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Operation and working environment
• To operate work equipment safely
– it must be fitted with easily reached and operated
controls,
– provided with adequate markings and warning signs.
• These are covered by PUWER 98, which applies to all
types of work equipment.
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Controls
• Equipment should be provided with efficient means
of:
– starting or making a significant change in operating
conditions;
– stopping in normal circumstances;
– emergency stopping as necessary to prevent danger.
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Controls
• All controls should be well positioned, clearly visible
and identifiable
• Markings should be clearly visible and remain so
under the conditions met at the workplace.
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Controls
(a) Start controls
– It should only be possible to start the work
equipment by using the designed start control
(b) Stop controls
– The action of normal stopping controls should
bring the equipment to a safe condition in a safe
manner.
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Controls
(c) Emergency stop controls
– Emergency stop must be provided where the other
safeguards in place are not sufficient to prevent danger
(d) Markings
– Markings on equipment must be clearly visible
– and durable.
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Two-hand Control
Emergency Switch

MMaacchhiinnee HHaazzaarrddss
Pictures or Graphs Within This Area
Unguarded Rotating Parts of Machine
Loose
Clothing

Unguarded Rotating Parts of
Machine
33.. MMaacchhiinnee HHaazzaarrddss

Controlling the Mechanical Hazards
• Following are the control measures:
– 1. Engineering controls.
– 2. Administrative controls.
– 3. Personal protective equipment.

Controlling the Mechanical Hazards
• The most effective controls are engineering controls
that physically change a machine or work
environment to prevent employee exposure to the
hazard.
• If this is not feasible, administrative controls may be
appropriate.
• This may involve changing how employees do their
jobs.

Engineering Controls
• Engineering controls include the following:
– Elimination/minimization of the hazard
– Substitution of equipment or process to decrease hazard
– Isolation of the hazard with interlocks, machine guards, or
other means; and
– Removal or redirection of the hazard such as with exhaust
ventilation.

Administrative Controls
• Administrative controls include the following:
– Written operating procedures, work permits, and safe work
practices;
– Exposure time limitations (used most commonly to control heat
stress and ergonomic hazards);
– Monitoring the use of highly hazardous materials;
– Alarms, signs, and warnings;
– and training

PPE
• Personal Protective Equipment is acceptable as a control
method in the following circumstances:
– When engineering controls are not feasible or do not totally
eliminate the hazard;
– While engineering controls are being developed;
– When safe work practices do not provide sufficient additional
protection; and
– During emergencies when engineering controls may not be
feasible.

Engineering Control
–Machine Safeguarding
– To determine the proper safeguarding
method, determine:
• Type of operation
• Size & shape of stock
• Method of handling
• Physical layout of work area
• Type of Material
• Production requirements or limitations

BASICS OF MACHINE GUARDING
 Requirements for Safeguards
 Be securely attached
 Create no new hazards
 Withstand operational conditions
 Allow for safe routine maintenance
 Allow for safe operator adjustments
 Withstand environmental conditions
 Provide protection from falling objects
 Prevent contact with hazardous conditions
 Create no interference in the conduct of work

METHODS OF MACHINE GUARDING
 Safeguards Are Grouped Under 5 Classifications:
1. Guards
2. Devices
3. Locations/Distance
4. Feeding and ejection methods
5. Miscellaneous aids

 Guards:
 Guards are barriers which prevent access to
danger areas, there are four general types:
 Fixed guards
 Interlocked guards
 Adjustable guards
 Self-Adjusting guards

Fixed guards
1.Guards
• A fixed guard has no moving parts and should, by its
design, prevent access to the dangerous parts of the
machinery
• it may be constructed of sheet metal, screen, bars,
plastic, or any other material
• This guard is usually preferable to all other types
because of its relative simplicity.
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44.. MMaacchhiinnee SSaaffeettyy
Machine Guard
Fixed Guard of Machine
1.Guards

1.Guards
 Fixed Guards:
ADVANTAGES
 Can be constructed to suit many different applications
 In-plant construction is often possible
 Can provide maximum protection
 Usually requires minimum maintenance
 Can be suitable to high production operations

1.Guards
 Fixed Guards:
LIMITATIONS
 May interfere with visibility
 Can be limited to specific operations
 Machine adjustments and repair often require guard
removal, thereby necessitating other means of protection
for maintenance personnel

 Interlocked Guards:
 Interlocked guards are designed to automatically
shut off the machine if the guard is opened or
removed
AUTOMATIC
AUDIBLE ALARM
AUTOMATIC
VISUAL ALARM
1.Guards

 Interlocked Guards:
1.Guards
• When this type of guard is opened or removed, the
tripping mechanism and/or power automatically
shuts off or disengages, the moving parts of the
machine are stopped, and the machine cannot be
started until the guard is back in place.
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1.Guards
METHODS OF MACHINE GUARDING  Interlocked Guards:
ADVANTAGES
 Can provide maximum protection
 Allows access to machine for removing jams without time
consuming removal of fixed guards
LIMITATIONS
 Requires careful adjustment and maintenance
 May be easy to disengage jams

 Adjustable Guards:
1.Guards
• Adjustable guards are useful because they allow
flexibility in accommodating various sizes of stock.
• Provides a barrier that may be adjusted to facilitate a
variety of production operations
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 Adjustable Guards:
1.Guards
ADVANTAGES
 Can be constructed to suit many specific applications
 Can be adjusted to admit varying sizes of stock
LIMITATIONS
 Hands may enter danger area
 Protection may not be complete at all times
 May require frequent maintenance and or adjustment
 The guard can be defeated by the operator

 Self-Adjusting Guards:
1.Guards
The openings of self-adjusted guards are determined by the
movement of the stock.
As the operator moves the stock into the danger area, the
guard is pushed away, allowing an opening that is large
enough to admit the stock.
When the stock is removed, the guard returns to the rest
position.
 Adjusts automatically to the work
 Accommodate various sizes of stock
 May require additional operator training
 Self-Adjusting guards are typically used on:
 Radial arm saws
 Table saws
 Circular saws
 Jointers
 Similar equipment

Machine Guard
1.Guards
Circular table
saw self-adjusting
guard
44.. MMaacchhiinnee SSaaffeettyy
Self-adjusting
Guard

 Self-Adjusting Guards:
1.Guards
ADVANTAGES
 they make varying sizes of work accessible to the point of
operation
Have wide variety of applications
LIMITATIONS
 Protection may not be complete at all times
 May require frequent maintenance and or adjustment

METHODS
OF
MACHINE
GUARDIN
 Devices:
 Devices fall into following general types:
G
 Presence-Sensing devices
 Pullback devices
 Restraint devices

METHODS  Devices: OF MACHINE GUARDING
 Devices may perform one of several function:
 Stop a machine if a body part is in danger
 Restrain or withdraw a hand if it is in danger
 Require activation by the use of both hands
 Provide a barrier synchronized to the operation

 Presence-Sensing:
2. Devices
 Typically operate on Photoelectric, Radiofrequency,
Electromechanical principle to disengage the machine when
something is detected in the hazardous area.
• These are typically installed on press and other machinery.
PRESS PRESS ACME
PRESSES

2. Devices

Pullback devices
2. Devices
• Pullback devices utilize a series of cables attached to
the operator's hands, wrists, and/or arms.
• This type of device is primarily used on machines
with stroking action.
• When the slide/ram is up between cycles, the
operator is allowed access to the point of operation.
• When the slide/ram begins to cycle by starting its
descent, a mechanical linkage automatically assures
withdrawal of the hands from the point of operation.
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 Pullback devices
ADVANTAGES
Eliminates the need for auxiliary barriers or other
interferences at the danger area
LIMITATIONS
2. Devices
 Limits movement of operator
 May obstruct work space around operator
 Adjustments must be made for specific operations and for
each individual
Requires close supervision of the operator's use of the
equipment

2. Devices
Restraint
• The restraint (hold-back) device utilizes cables or
straps that are attached to the operator's hands and
a fixed point.
• The cables or straps must be adjusted to let the
operator's hands travel within a predetermined safe
area.
• There is no extending or retracting action involved.
Consequently, hand-feeding tools are often
necessary if the operation involves placing material
into the danger area.
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 Restraint devices
ADVANTAGES
Simplicity of use
LIMITATIONS
2. Devices
 Limits movement of operator
 May obstruct work space around operator
 Adjustments must be made for specific operations and for
each individual
Requires close supervision of the operator's use of the
equipment

3. Location/Distance Safeguarding:
 Position Dangerous Areas of Machines So That They Are
Not Assessable During Normal Operations. Examples
Include:
 Position Hazard Areas Against a Wall
 Locate Hazards Out of Reach of Operators
 Design Stock Feeding Openings Away From Hazards
 Position the Operators Control Station Away From Hazards

4. Feeding and Ejection Methods:
 Automatic and Semiautomatic feeding and ejection of
parts are other ways of safeguarding machine
processes.
 These methods eliminate the need for the operator to
work at the point of operation.
 In some situations, no operator involvement is
necessary after machine is set up.
 In other cases, operators can manually feed the stock
with assistance of a feeding mechanics.
 Properly designed ejection methods do not require
any operator involvement after machine starts to
function.

5.Miscellaneous Aids
• While these aids do not give complete protection
from machine hazards, they may provide the
operator with an extra margin of safety.
– Awareness Barriers
– Protective Shields (protection from flying debris)
– Hand-Feeding Tools
– Administrative Controls
– Personal Protective Equipment (PPE)
09/20/14 83

Mechanical hazard control

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