osha 10 hour machine guarding presentation #4

A good rule to remember is:

Any machine part, function, or process which may cause injury must be safeguarded.

Where the operation of a machine or accidental contact with it can injure the operator or others in the vicinity, the hazards must either be eliminated or controlled.

If it moves, it merits your attention!

1. Describe the basic hazards involving machinery including point of operation and power transmission devices.

2. Introduce control measures through effective machine guarding

principles and methods.

Goals

1910.212(a)(1) Types of guarding• One or more methods of machine guarding shall be

provided to protect the operator and other employees in the machine area from hazards such as those created by: – Point of operation,

– Ingoing nip points,

– Rotating parts,

– Flying chips and sparks

The point where work is actually performed.

Cutting

Shaping

Boring

Forming

Point of Operation Hazards

The purpose of machine guarding is to protect against and prevent injury from....

Point of operation

Nip points

Part One: The Principles


Point of operation

Nip points

Rotating parts




Point of operation

Nip points

Rotating parts

Flying Chips



Point of operation

Nip points

Rotating parts

Flying Chips

Sparks

Where Mechanical Hazards Occur

Three basic areas require safeguarding


1. Point of Operation

The components which transmit energy to the part of the machine performing the work.


2. Power Transmission Devices

Flywheels Pulleys

Rods Cams

Couplers Spindles

Chains Sprockets

Gears Shafts

Cranks Belts


2. Power Transmission Devices

All hazardous parts which move while the machine is working.

Reciprocating

Rotating

Transverse

Feed mechanisms


3. All Other Moving Parts

Hazardous Mechanical Motions and Actions

A wide variety of mechanical motions and actions may present hazards to the worker.

• Rotating or reciprocating members

• Moving belts

• Meshing gears

• Cutting teeth

• Any part that impacts or shears

What are some hazards of rotating parts?

Rotating Motion

1. Parts rotating in opposite direction

In-running nip point hazards

Rotating Motion

2. Rotating and tangentially moving parts


Rotating Motion

3. Rotating and fixed parts


Rotating Motion

Reciprocating Motion

Transverse Motion

Standard Interpretations 12/20/1994 - Machine-guarding

requirements• By not specifying the types of machine guards that

must be used, this standard is referred to as a "performance" standard (i.e., the employer is free to adopt a machine guard that "performs" in such a manner as to meet the standard's objective--to protect employees from the identified hazards).

• If OSHA had specified the types of machine guards that must be used, the standard would be a "specification" standard.

Must prevent any contact to the machine hazard and installed to prevent contact from around, over, through, or under the guard!

“…so designed and constructed as to prevent the operator from having any part of his/her body in the danger zone during the operating cycle”

{29 CFR 1910.212(a)(3)(ii)}

Effective Safeguarding

• Must be in conformity with any appropriate standards

• Must not present a hazard in itself nor create interference


• Must not allow objects to fall into moving parts

• Allow safe maintenance and lubrication

• Must be affixed and secured to the machine where possible


There are many ways to safeguard machines!

Determine the appropriate safeguarding method.

Consider

• the type of operation and material

• the size or shape of stock

• the method of handling

• the physical layout of the work area

• production requirements/limitations

Part Two: Safeguarding

As a general rule, power transmission apparatus is best protected by fixed guards that enclose the danger areas.

Enclosed shaft end


Enclosed chain & sprocket

For hazards at the point of operation, several types of safeguarding may be considered.

Because safeguarding the point of operation can provide challenges, one must always choose the most effective and practical means available.

Let’s take a look at some strategies


1. Guards

Fixed

Interlocked

Adjustable

Self-adjusting


2. Devices

Presence Sensing

Pullback

Restraint

Safety Controls

Gates


Rockford Systems, Inc.

3. Location/Distance

4. Feeding/Ejection Methods

Automatic/Semi-Auto feed Automatic/Semi-Auto ejectionRobotics


Guard was hanging at the work bench!

Effective?

Guards are barriers which prevent access to danger areas.

First Safeguarding Strategy: Guards

Fixed Guards

– A permanent part of the machine

– Not dependent upon moving parts to perform its intended function

– Constructed of sheet metal, screen, wire cloth, bars, plastic, or substantial material

– Usually preferable to all other types because of its simplicity and

permanence


Interlocked Guards

When this type of guard is opened/removed

– the tripping mechanism and/or power automatically

shuts off or disengages

– the machine cannot cycle or be started until the guard is back in place


Interlocked Guards

– They may use electrical, mechanical, hydraulic, or pneumatic power or

any combination of these

– Replacing the guard should not automatically restart the machine


Interlocked Guards

Interlocked guarding can be defeated!

This was taped down.

Adjustable Guards

– These guards allow flexibility in accommodating various sizes of

stock


Self-Adjusting Guards

The openings of these guards are determined by the movement of the stock.

– As the operator moves the stock into the danger area, the guard is pushed away, providing an opening which is only large enough to admit the stock

– After the stock is removed, the guard returns to the rest

position


Self-Adjusting Guards

A safety device may perform one of several functions.


Second Safeguarding Strategy: Devices

Presence-Sensing Devices

Photoelectric (optical)

– Uses a system of light sources and controls which can interrupt the machine's operating cycle


• It may stop the machine if a hand or any part of the body is

inadvertently placed in the danger area

Equipment Resale, Inc



Radiofrequency (capacitance)

– Uses a radio beam that is part of the machine control circuit

– When the capacitance field is broken, the machine will stop or will not activate



Electromechanical

– Has a probe or contact bar which descends to a predetermined distance when the operator initiates the machine cycle

– If there is an obstruction preventing it from descending its full predetermined distance, the control circuit does not actuate the machine cycle


• Restrain or withdraw the operator's hands from the danger area

during operation



Pullback

– 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


Restraint

– The restraint (holdout) device utilizes cables or straps that are attached

to the operator's hands at 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


• Require the operator to use both hands on machine controls



Two Hand Controls

– Requires constant, concurrent pressure by the operator to activate the machine

– With this type of device, the operator’s hands

are required to be at a safe location (on the

control buttons) and at a safe distance from the danger area


Two Hand Trips

– This device requires concurrent application of both the operator’s

control buttons to activate the

machine cycle, after which the hands are free.


Safety Trip Controls

– Provide a quick means for deactivating the machine in an emergency situation

– A pressure-sensitive bar, when depressed, will

deactivate the machine


Safety Trip Controls

– Safety tripwire cables may also be located around the perimeter or near the danger area


• 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



Gates

– A gate is a movable barrier which protects

the operator at the point of operation

before the machine cycle can be

started

– Usually designed to operate with each

machine cycle


Guarding by Location/Distance

– The machine or its dangerous moving parts are positioned so that hazardous areas are not accessible or do not present a hazard during normal operation

– walls or other barricades (fences)

– height (above worker)

– size of stock (single end feeding, punching)

Another Safeguarding Strategy

Is this adequate distance?

Is this adequate location?

Feeding and Ejection

– Automatic and Semiautomatic Feeding



– Automatic Ejection



– Semiautomatic Ejection


Robotics

– Machines that load and unload stock, assemble parts, transfer objects,

and perform other tasks

– They perform work otherwise done by the operator

– Best used in high production processes requiring repeated routines


Robotics

Does not give complete protection from machine hazards, but may provide the operator with an extra margin of safety.

Examples:

•Awareness barriers

•Shields

•Holding tools

•Push sticks or blocks

Miscellaneous Aids

1910.212(a)(3)(iii) Hand Tools• Special hand tools for placing

and removing material shall

be such as to permit easy

handling of material without

the operator placing a hand in

the danger zone* *Such tools shall not be in lieu of other guarding

required by this section, but can only be used to

supplement protection provided.

1910.212(a)(3)(iv) Examples of machines

• Types of machines which normally require point

of operation guarding:

– Mills

– Drills

– Grinders

– Power presses

– Shears

– Saws

1910.212(a)(4) Barrels, containers, and drums

• Revolving drums, barrels,

and containers shall be

guarded by an enclosure

which is interlocked with

the drive mechanism, so

that the barrel, drum, or

container cannot revolve

unless the guard

enclosure is in place

1910.212(a)(5) Exposure of blades• When the periphery of the blades of a fan is

less than seven (7) feet above the floor or

working level, the blades shall be guarded

• The guard shall have openings no larger than

one-half (1/2) inch.

1910.212(b) Anchoring fixed machinery

• Machines designed for a fixed location shall be

securely anchored to prevent walking or moving

This pedestal grinder is designed for anchoring,

and is not anchored, creating a potential

hazard

CPL 2-1.35 National Emphasis Program on Amputations

• Identify and reduce workplace hazards likely to cause amputations

• top five machines that cause amputations are: – Saws, – Shears, – Slicers, – Slitters, and – Presses.

Saws• Used primarily in woodworking and

manufacturing shops• Two types

– Table – Radial arm

• Other types include:

Hand heldBand saw Miter saw

Shears

• Self-contained machines using a mechanically

driven ram

• Ram moves a nonrotary blade at a constant

rate past the edge of fixed blade

Slicers• Commonly used to slice meat

and food

• Use rotary blade

• Guillotine cutters used in other

industries

• Most injuries occur in

restaurants and grocery

stores

Power Presses

• NEP covers all types of

power presses

• Presses consist of

stationary bed, and slide

• Used in a variety of

industries

Program Procedures

• NEP includes three

activities:

– Outreach

– Targeting/selection

– Inspection

• If present, a thorough

inspection will be

conducted focusing on:

– Nip points

– Pinch points

– Shear points

– Cutting actions

– Point(s) of operation

1910.213(a)(12) Guarding blades under tables

• For all circular saws where conditions are such that there is a possibility of contact with the portion of the saw either beneath or behind the table, that portion of the saw shall be: – Covered with an exhaust hood, or, if no exhaust

system is required,

– With a guard that shall be arranged as to prevent accidental contact with the saw

1910.213(b) Machine controls and equipment

• A mechanical or electrical power

control shall be provided on

each machine to make it

possible for the operator to cut

off the power from each

machine without leaving his

position at the point of operation

1910.213(b)(3) Non-restart devices

• On applications where injury to the operator

might result if motors were to restart after

power failures, provision shall be made to

prevent machines from automatically restarting

upon restoration of power

1910.213(b)(4) Location of controls

• Power controls and operating

controls should be located

within easy reach of the

operator while he is at his

regular work location, making

it unnecessary for him to

reach over the cutter to make

adjustments

1910.213(c) Ripsaws• Each circular hand-fed ripsaw shall be guarded

by a hood which shall completely enclose that

portion of the saw above the table and that

portion of the saw above the material being cut

• Each hand-fed circular ripsaw shall be

furnished with a spreader to prevent material

from squeezing the saw or being thrown back

on the operator

1910.213(c)(2) Spreaders

Spreader

1910.213(c)(3) Non-kickback fingers• Each hand-fed circular

ripsaw shall be

provided with non-

kickback fingers or

dogs so located as to

oppose the thrust or

tendency of the saw to

pick up the material or

to throw it back toward

the operator

1910.213(g)(1) Swing cutoff saws

• Each swing cutoff saw shall be provided with a

hood that will completely enclose the upper half

of the saw, the arbor end, and the point of

operation at all positions of the saw

• Each swing cutoff saw shall be provided with an

effective device to return the saw automatically

to the back of the table when released at any

point of its travel

1910.213(g)(2) Swing cutoff saws

1910.213(h) Radial saws• The upper hood completely encloses the upper portion

of the blade down to a point that will include the end of the saw arbor

• Radial saws used for ripping provided with nonkickback fingers or dogs located on both sides of the saw so as to oppose the thrust or tendency of the saw to pick up the material or to throw it back toward the operator

1910.213(i) Bandsaws

• All portions of the saw blade shall be enclosed

or guarded, except for the working portion of the

blade between the bottom of the guide rolls and

the table

1910.213(i) Bandsaws• Bandsaw wheels shall be

fully encased

• The outside periphery of

the enclosure shall be

solid

• The front and back of the

band wheels shall be

either enclosed by solid

material or by wire mesh

or perforated metal

Treadle

• Each operating treadle shall be covered by an

inverted U-shaped metal guard, fastened to the

floor, and of adequate size to prevent

accidental tripping

1910.215(a)(2) Guard design• The safety guard shall cover

the spindle end, nut, and flange

projections

• The safety guard shall be

mounted so as to maintain

proper alignment with the wheel

1910.215(a)(2) Guard design• The strength of the fastenings shall exceed the

strength of the guard, except:

– Where the work provides suitable protection, the

guard may expose the spindle end, nut and flange

– Where the work entirely covers the side of the

wheel the side cover(s) of the guard may be omitted

1910.215(a)(4) Work Rests• On off hand grinding, work rests are required, to support

the work• Rigid construction, and adjustable with wheel wear• Must be kept closely adjusted, max gap = 1/8" to prevent

work from jamming & breaking wheel

• Securely clamped after each adjustment• Adjustments made only when wheel is stopped

Work rest is closelyadjusted

1910.215(b)(9) Exposure adjustment

• Safety guards of the type where the operator stands in front of the opening, shall be so constructed so that the peripheral protecting member can be adjusted to the constantly decreasing size of the wheel

• The distance between the periphery and the adjustable tongue guard shall never exceed one-fourth inch

1910.215 (d) Mounting• Inspection:

– Immediately before mounting, all wheels shall be closely

inspected and sounded by the user (ring test) to make sure they

have not been damaged in transit, storage, or otherwise

– The spindle speed of the machine shall be checked before

mounting of the wheel to be certain that it does not exceed the

maximum operating speed marked on the wheel

• Sound the wheel by tapping around the wheel periphery with a wood handled screwdriver*

• Good wheel portions will “ring” like a bell

• Cracks will sound “dead”

1910.215 (d) Mounting -Ring Test

*A non-metallic implement, wood mallets may be needed for larger wheels

• The spindle speed of the machine shall be checked before mounting of the wheel to be certain that it does not exceed the maximum operating speed marked on the wheel.

1910.215 (d) Mounting

Compare this number to the spindle speed on the grindermotor

Definitions• "Full revolution clutch" means a type of clutch

that, when tripped, cannot be disengaged until

the crankshaft has completed a full revolution

and the press slide a full stroke.

• "Part revolution clutch" means a type of clutch

that can be disengaged at any point before the

crankshaft has completed a full revolution and

the press slide a full stroke.

1910.217(c)(2) Point of operation guards

• It shall prevent entry of hands or fingers into the

point of operation by reaching through, over,

under or around the guard;

• It shall conform to the maximum permissible

openings of Table O-10;

Table O-10 [In inches]___________________________________________________ | Distance of opening from point | Maximum width of of operation hazard | opening____________________________ |__________________ |

1/2 to 1 1/2 ................. | 1/41 1/2 to 2 1/2 ............... | 3/82 1/2 to 3 1/2 ............... | 1/23 1/2 to 5 1/2 ............... | 5/85 1/2 to 6 1/2 ............... | 3/46 1/2 to 7 1/2 ............... | 7/87 1/2 to 12 1/2 .............. | 1 1/412 1/2 to 15 1/2 ............. | 1 1/215 1/2 to 17 1/2 ..........… | 1 7/817 1/2 to 31 1/2 ............. | 2 1/8

____________________________ |__________________

• Preventing and/or

stopping normal

stroking of the press

if the operator's

hands are

inadvertently placed

in the point of

operation;

Presence sensing device


• Requiring application of both of the operator's hands to machine operating controls and locating such controls at such a safety distance from the point of operation that the slide completes the downward travel or stops before the operator can reach into the point of operation with his hands; or


Presence sensing devices

• The device may not be used on

machines using full revolution clutches!

1910.217(c)(3)(iv)(d) Pull-out device

• Each pull-out device in use shall be visually inspected and checked for proper adjustment at the start of each operator shift, following a new die set-up, and when operators are changed.

• Necessary maintenance or repair or both shall be performed and completed before the press is operated.

• Records of inspections and maintenance shall be kept in accordance with paragraph (e) of this section.

Pullbackdevice

Adjustablewrist

straps

1910.219(b)(1) Flywheels• Flywheels 7 feet or less above

the ground shall be guarded• Sheet, perforated, or expanded

metal or woven wire, or with• Guard rails between 15 to 20

inches from flywheel rim• Toe board if within 12 inches of

floor or extends into a pit• All projections shall be covered

1910.219.(c) Shafting

• Each continuous line of shafting shall be

secured in position against excessive end

movement

• Inclined and vertical shafts* shall be securely

held in position against endwise thrust

*Particularly inclined idler shafts

• All exposed parts of horizontal shafting 7 ft. or less above

the floor shall be guarded (except: runways used for

oiling or running adjustments) by a stationary casing, or

by a trough

• Troughs must enclose sides and top, or sides and

bottom of shafting as location requires


Projecting end shafts shall

present a smooth edge

and project not more than

1/2 the diameter of the

shaft

Unused key ways shall be

filled up or covered


1910.219(d) Pulleys• Pulleys, any parts of which are seven feet or less from

the floor or working platform, shall be guarded in

accordance with the standards specified in paragraphs

(m) & (o)

• Pulleys serving as balance wheels (e.g., punch presses)

on which the point of contact between belt and pulley is

more than six feet six inches from the floor or platform

may be guarded with a disc covering the spokes

Distance between pulleys = 2 inches

Belt width = three inches

Guides must be placedin this area

Example

seven ft. minimumFloor

Unguarded portion

Guard

1910.219 (f) Gears sprockets and chains

• Gears, sprockets and

chains shall be guarded by

one of the following

methods:

• By a complete enclosure; or

• By a standard guard as in

paragraph (o), at least

seven feet high, extending

six inches above the mesh

point of the gears; or

osha 10 hour machine guarding presentation #4

Business

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operation hazardsthe

operation nip points

nip point hazards2

nip point hazards1

rotating motionin

point of operationcan