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Farm Safety Association, Inc.
A
PTO shaft revolving at 540 rpm travels more than two meters
in less than a second. Little wonder that PTO entanglement nearly
always results in devastating injury or death!
Missing
or damaged shielding is the main reason for driveline entanglement.
Manufacturers have made tremendous strides in developing safer
PTO shielding. However, it is impossible to make protection
fool proof. All shielding components must be correctly installed
and properly maintained to prevent injury in case of accidental
contact.
Operator
awareness and constant vigilance are also crucial if PTO entanglement
is to be avoided. Making repairs while equipment is operating,
stepping over or onto revolving shafts, wearing loose or frayed
clothing are actions that set the stage for carnage.
Clear
safety rules must be established for everyone who works with
farm machinery. Even the most experienced operator will benefit
by reviewing the PTO safety information summarized in this
fact sheet. The guidelines will prove especially valuable
for training novice equipment operators -- new employees and
children who are excited about the prospect of operating farm
machinery must be made aware of the importance of sticking
to these rules!
A tractor's master shield prevents accidental contact with the tractor stub shaft and the front universal joint of the attached machine's driveline. Never operate a tractor with a missing or damaged master shield.
Integral-journal
shields completely enclose the power shafts of PTO-operated
machines. Manufacturers have made great strides in the design
of these tubular shields, most of which are now made of durable
plastic. The "cones" that cover the universal joints at each
end of a plastic power shaft shield have also been improved
- their flexible design makes hook-up easier and provides
greater protective cover.
Integral
shields rotate on bearings, independently of the power shaft.
They revolve with the shaft while it is turning, but the shield
will stop spinning if it is contacted. These shields must
be kept in place and maintained in good condition to provide
protection against the grabbing action of shafts and universal
joints.
The power
shaft must also be shielded at the point of attachment of
the driven machine. Both the universal joint and the machine's
stub shaft must be well covered. If this shielding is missing
or damaged, or if you feel it doesn't provide adequate protection,
talk to your dealer about a replacement.
There
are still some older machines in operation that have tunnel
shields over their power shafts. This design offered only
limited protection. Because tunnel shielding is still open
at the bottom, clothing, shoelaces, hair, etc. can be caught
by the shaft or universal joints. There is a case to be made
for "retiring" such equipment. If it must be used, power shafts
and shielding should be replaced with safer, modern components.
A PTO shaft
may break or separate during operation if improperly used or
adjusted. If it does, the tractor-driven end can swing violently,
with the potential for severe equipment damage and operator
injury.
New equipment
is fitted with the driveline recommended for that particular
machine. Make very sure that all replacement driveline components
conform to the same specifications.
The tractor
drawbar should be adjusted to the length specified in the
driven machine's manual. This ensures that the telescoping
power shaft and shield will stay together when they lengthen
in operation. It also prevents driveline "bottoming out" when
making a sharp turn, or when the rear tractor wheels enter
a depression. This puts considerable strain on shaft and bearing
supports, and the entire driveline may be damaged or bent.
To perform
its intended function, farm machinery has to operate in a very
powerful, aggressive fashion. Operators must adopt good safety
habits to prevent injury, even with well-shielded equipment.
Following
are key considerations for preventing PTO entanglement.
- Always
disengage the PTO, shut off the engine and remove the keys
before leaving the tractor seat. You can't be injured
by the PTO or other machine parts if the driveline isn't
rotating! Taking the keys prevents unexpected start-up by
another person while you are cleaning, lubricating, adjusting,
or making repairs.
- Keep
the tractor's master shield in place at all times.
- Check
frequently to confirm that integral shields are in good
condition. With the powershaft stopped, you should be
able to rotate the shield freely by hand. Look for nicks,
dents or bends that could catch clothing. Damaged shields
or bearings must be repaired immediately. Don't operate
the machine until damaged parts are fixed or replaced.
- Never
step across a rotating powershaft. Some equipment must
be operated in a stationary location where you are working
(e.g. forage wagons and blowers, grinder-mixers, etc.) When
such machines are running, always walk around the revolving
shaft. Safety devices are usually reliable, but could malfunction.
- Dress
for safety. Wear close fitting clothes and keep long
hair covered. Raggy old coats and long boot laces can easily
be grabbed by rotating parts.
Broken bones,
severed limbs, crushed skulls--such horrendous injuries are
typical of PTO entanglement accidents. The only sure way to
prevent such tragedy is to avoid all contact with moving machine
parts. Good shielding is vital, but all equipment operators
must be aware of hazards and make safety a part of their habitual
behaviour.
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Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
The information
and recommendations contained in this publication are believed
to be reliable and representative of contemporary expert opinion
on the subject material. The Farm Safety Association does not
guarantee absolute accuracy or sufficiency of subject material,
nor can it accept responsibility for health and safety recommendations
that may have been omitted due to particular and exceptional
conditions and circumstances.
Fact
Sheet
NO.
F-020
DECEMBER 1992
Copyright© 1992
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