Hazards of Mechanical Power Presses
Power presses (mechanical, hydraulic and pneumatic) can be dangerous machines and account for a large number of workplace amputations.
Amputations occurring from the point of operation hazards are the most common types of injuries associated with mechanical power presses. Improperly applied safeguarding methods may allow operators unsafe access to the press’s hazardous area. These unsafe conditions may result in an amputation when an operator, for example, instinctively reaches into the point of operation to adjust a misaligned part or release a jam. Also, amputations occur when an operator’s normal feeding rhythm is interrupted, resulting in inadvertent placement of the operator’s hands in the point of operation. Such injuries usually happen while the operator is riding the foot pedal. Additionally, some amputations are linked to mechanical (such as the failure of a single-stroke linkage), electrical (such as a control relay failure), or pneumatic (such as the loss of air pressure to the clutch/brake) machine component failure.
Examples of inadequate or ineffective safeguarding and hazardous energy control practices include the following:
Guards and devices disabled to increase production, to allow the insertion of small-piece work, or to allow better viewing of the operation.
Two-hand trips/controls bridged or tied-down to allow initiation of the press cycle using only one hand.
Devices such as pullbacks or restraints improperly adjusted.
Controls of a single-operator press bypassed by having a coworker activate the controls while the operator positions or aligns parts in the die, or repairs or troubleshoots the press.
Failure to properly disable, isolate press energy sources, and lockout/tagout presses before an employee performs servicing or maintenance work.Controls for Machines with Clutches:
Full-revolution clutches, once activated, complete a full cycle of the slide (lowering and raising of the slide) before stopping at dead center and cannot be disengaged until the cycle is completed. So, presence-sensing devices will not work and operators must be protected during the entire press operating cycle. For example, properly applied barrier guards or two-handled trip devices that are installed at a safe distance from the hazard area may be used. Machines incorporating full-revolution clutches, such as mechanical power presses, must also incorporate a single-stroke device and anti-repeat feature.
The majority of part-revolution presses are air clutch and brake. They are designed to trap air in a chamber or tube. When the compressed air is put into these chambers, the clutch is engaged, the brake disengaged and the press makes a single stroke. To stop the press, the reverse takes place. Thus, the part-revolution clutch can be disengaged at any time during the cycle to stop the cycle before it completes the down stroke. For safeguarding purposes, part-revolution mechanical power presses can be equipped with presence-sensing devices, but full-revolution mechanical power presses cannot.
OSHA Case History #1
While using an unguarded, foot-pedal-operated, full-revolution mechanical power press that made trip collars for wood stoves, an employee used his hands to feed and remove finished parts and scrap metal. He placed the completed part to the left side of the press, and then turned to place the scrap in the bin behind him. As he turned back to face the press, he inadvertently stepped on the foot pedal and activated the press while his hand was in the die area. His left hand was amputated at the wrist.
OSHA Case History #2
An employee was operating an unguarded 10-ton, full-revolution mechanical power press to stamp mailbox parts, and using a hand tool to load the press, she placed her left hand in the lower die to reposition a misaligned part. At the same time, she inadvertently depressed the foot pedal, activating the press and crushing her left index finger.
OSHA Case History #3
A power press operator and helper were instructed to temporarily halt production and each employee decided to perform servicing tasks. The operator had a problem with a hydraulic fluid leak and decided to deflect the liquid spray by installing a temporary barrier while, at the same time, the helper decided to clean up the metal chips from the press area. The operator then activated the press and repositioned the press slide in order to install the cardboard barrier. This mechanical power press action fatally crushed the helper’s head because his head was between the dies while he was in the process of cleaning up the metal chips.
Source: OSHA IMIS Accident Investigation Database.
Safeguarding Mechanical Power Presses
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Watch our VIDEO on two-hand control
Watch our VIDEO on die safety blocks
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Mechanical power presses are extremely versatile and selecting appropriate safeguarding methods depends on the specific press design and use. You should consider the press, the type of clutch used, the stock size, the length of production runs, and the method of feeding.
You can use primary safeguarding methods, such as guards or safeguarding devices, to prevent injuries. For example, 29 CFR 1910.217 requires employers to provide and ensure the use of point of operation guards or properly installed devices on every operation performed on a press when the die opening is greater than 1/4 inch.
In addition, guards must conform to the maximum permissible openings of Table O-10 of 29 CFR 1910.217. Guards must prevent entry of hands or fingers into the point of operation through, over, under, or around the guard.
“No Hands-in-Die” Policy
In general, a “No-Hands-in-Die” policy needs to be implemented and followed whenever possible — that is, in the event the press is not designed for “hands-in-die” production work. Under this policy, operators must never place their hands in the die area (point-of-operation) while performing normal production procedures. Adherence to this safety practice will reduce the risk of point of operation amputations.
In terms of part-revolution mechanical power presses that use a two-hand control, presence-sensing device or type B gate, OSHA does allow “hands-in-die” operation if the press control reliability and brake monitoring system requirements are met. If these press design safety features are not complied with, then employers must incorporate a “no-hands-in-die” policy.
Source: 29 CFR 1910.217(c)(5)
Inspection, Maintenance and Reporting
29 CFR 1910.217(e)(1)(i) requires a program of periodic and regular inspections of mechanical power presses to ensure that all of the press parts, auxiliary equipment and safeguards are in safe operating condition and adjustment. Inspection certification records must be maintained.
29 CFR 1910.217(e)(1)(ii) requires you to inspect and test the condition of the clutch/brake mechanism, anti-repeat feature, and single-stroke mechanism on at least a weekly basis for presses without control reliability and brake system monitoring. Certification records must be maintained of these inspections and the maintenance performed.
29 CFR 1910.147, Control of hazardous energy (lockout/tagout).
29 CFR 1910.217, Mechanical power presses.
29 CFR 1910.219, Mechanical power-transmission apparatus
OSHA Instruction CPL 3-00-002 [CPL 2-1.35], National Emphasis Program on Amputations
OSHA Publication 3067, Concepts and Techniques of Machine Safeguarding(http://www.osha.gov/Publications/Mach_SafeGuard/toc.html)
OSHA Machine Guarding eTool (http://www.osha.gov/SLTC/etools/machineguarding/index.html)
OSHA Lockout/Tagout Interactive Training Program(http://www.osha.gov/dts/osta/lototraining/index.html)
NIOSH CIB 49, Injuries and Amputations Resulting From Work with Mechanical Power Presses (May 22, 1987)
OSHA Instruction STD 01-12-021 [STD 112.21] — 29 CFR 1910.217, Mechanical Power Presses, Clarifications (10/30/78)
ANSI B11.1-2001, Safety Requirements for Mechanical Power Presses
For more information on safeguarding power presses, please contact 1-800-922-7533 or email@example.com to schedule a machine safeguarding assessment.