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Power Presses - Partial Revolution Power Presses |
Printing Instructions
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Appendix I
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Appendix I: MECHANICAL POWER PRESS QUESTIONS AND ANSWERS
- Scope of the Standard
- Control Systems & Brake Monitor
- Presence Sensing
- Pull-outs and Sweeps
- Two Hand Trip & Controls
- Type A & B Gates
- Barrier Guards & Other
Safeguards
- Safety Distance
- Record Keeping
- Minimum training requirements for power press operators
- Minimum training requirements for power pressroom supervisors
Note:
Under no circumstances will the following be used in lieu of the specific
language of the law, and final determination of the requirements must be checked
with OSHA. Several questions and answers are referenced according to specific
sections of the law in an attempt to provide compliance assistance to interested
parties.
I. SCOPE OF THE STANDARD
- Q. Does the standard for mechanical power presses
cover these presses when other materials are being worked such as nonferrous metals,
plastic materials, or other materials?
A. Yes.
- Q. Are press brakes
covered by the standard for mechanical power presses?
A. No
- Q. If a press
brake is fitted with dies and functions as a mechanical power press, is
safeguarding required?
A. Yes
- Q. What type
of presses or other metal working machines are exempt from Section 29 CFR 1910.217?
A. Some types of presses not covered by 29 CFR 1910.217 are
envelope making (window cutters, etc.) machines, dinkers
and clickers used for cutting leather and other materials, brick presses, broaching
machines, abrasive wheel presses, platen presses, powdered metal presses, hot bending and forming machines, forging
presses.
- Q. Are hot
bending operations covered by Section 29 CFR 1910.217
A. No
II. CONTROL SYSTEM & BRAKE MONITOR
- Q. For
ungrounded circuits, is the first ground considered a failure?
A. No
- Q. When
operating a successive continuous run, is a single failure in the press control
system required to stop the press?
A. No, it prevents a successive continuous run
being initiated.
- Q. If a
press is only operated on continuous, must a single stroke mechanism be
provided?
A. No, however, special attention needs to be
given to die changing operations. Die setters do not normally
re-install barrier guards to run try-out pieces. In these cases a single stop mechanism
would be required.
- Q. If a
press stroke cannot be initiated because of the brake monitor action, how is
this indicated to the operator?
A. The control system may have an indicator light
or alarm. The visual inspection of markings on the
crankshaft will show that press slide has not stopped within the safe range previously
established. The press won't run.
- Q. If the brake
monitor is actuated by top stop overrun, can the brake initiation point be set
earlier in the cycle if the safety distance is recalculated and two-hand controls moved?
A. Yes, this practice is allowed as long as the brake is
deemed to be functioning within its stopping time limit before overhaul and repairs are required.
- Q. If a press
stops at some point of the cycle due to the brake monitor, how is the press
slide returned to top of stroke?
A. The inch controls or other bypass circuits are used to
return press slide to top of stroke.
- Q. Must brake
monitors detect brake deterioration when the brake is applied at other than top
of stroke?
A. No, but some types of brake monitors will give an
indication of stopping time on each brake application at
any point in the stroke.
- Q. Can a press be
operated on-the-hop with a brake monitor?
A. No, the press slide must stop on each stroke for the brake
monitor to be effective.
- Q. Is a brake
monitor necessary on a full revolution clutch press?
A. A brake monitor is not required on a full revolution clutch
press. Brake monitor manufacturers and users
are claiming that they are feasible and useful on a full revolution clutch
press.
III. PRESENCE SENSING
- Q. Do presence
sensing devices require some form of additional safeguarding to protect press
operators?
A. Yes, if there are areas of entry to the point of
operation not protected by the sensing device, then other safeguarding is
required.
- Q. What are the
limits of muting of a presence sensing device to enable parts ejection, feeding,
or circuit checking?
A. Muting of such devices is only permitted during the up stroke of
the press slide.
IV. PULLOUTS & SWEEPS
- Q. Are pull-outs
acceptable for safeguarding the press operator when press stroke is actuated by
a foot
pedal or a two-hand trip not meeting the required safety distance?
A. Yes, the pull-outs by themselves are recognized as an
acceptable safeguard.
- Q. Why are
detailed requirements given for checking and adjusting of pull-outs?
A. Pull-outs are a more personal form of safeguard whose
proper functioning can be affected when
operators are changed, or a new die set for operation. Visual inspection of pull-outs can
detect wear of parts as well as proper action when press is stroking.
- Q. Can a restraint be
used for "hands in dies" feeding?
A. No. By definition the restraint does not permit entry of
the hand into the die or point of operation.
- Q. Can a restraint
used for one hand be used in conjunction with a single trip or control button
for the second
hand, when the second hand is used for feeding into the point of operation.
A. Yes, if a safety distance is established for the one-hand
trip or control button.
- Q. What is the
difference between a restraint and a pull-out device?
A. A
restraint prevents entry of hands or fingers to the point of operation at all
times, while a pull-out device
allows hand-in-dies for feeding.
- Q. Are restraints or hold-outs a recognized form of
safeguarding a point of operation hazard?
A. Yes,
restraints which keep operators' hands out of the point of operation at all
times are an acceptable safeguard.
- Q. Are two-hand trips recognized as an acceptable means of
safeguarding the operator from the hazard of the
point of operation?
A. Yes, providing the safety distance between the point of
operation and the two-hand trips is determined by the appropriate formula.
V. TWO HAND TRIP
&
CONTROLS
- Q. What are some of the methods or means used to fix the
position to two-hand trips or controls as the safety distance?
A. Articulating or extendable bars or control mounts, clearly
established floor position for portable control
stands, or other administrative controls may be used when it is not possible to
mechanically or electrically fix the portable
stand or station on position.
- Q. What methods are used to fix the position of two-hand trips
or controls?
A. Key-locked control stations; key-locked portable control
stands; removable plug-in control stations; portable stand floor location fittings; portable stand bases which establish a
safety distance; movable
control bars or buttons fixed by fasteners which require the use of special tools to
remove.
- Q. Must "holding time" cover the entire period of die closing
or until the hazard of die closing ceases at 1/4 inch opening?
A. No, holding time can be set for any period of time during
the cycle. Press stopping time is the critical factor in establishing the safety distance for safeguarding means.
VI. TYPE A & B GATES
- Q. Is a Type A gate an acceptable safeguard with a two-hand
trip or two-hand control without adequate safety
distance determined by the the appropriate formula?
A. Yes, the Type A gate alone will satisfy the requirements
for safeguarding with any form of press actuation such
as foot pedal or control, two-hand trip or control without safety distances, or
others such as one-hand trip.1
- Q. Can a Type A gate be opened during the downstroke of the
slide? 29 CFR 1910.217(c)(3)(ii)(a)
A. No, a Type A gate remains closed.
- Q. Can a Type B gate be opened during the downstroke of the
slide? 29 CFR 1910.217(c)(3)(i)(g)
A. The Type B gate, when used on a part revolution clutch
press, should be designed so that it is held closed during the closing portion of the stroke. If it can be manually opened during
the closing portion of the stroke, the gate must be located so that the point of operation cannot be reached prior
to the slide stopping.
This can be accomplished by applying the same safety distance formula used for
placement of two hand controls and presence sensing devices.
- Q. When manual feeding with hands in die, can a Type B gate or
movable barrier device be used for safeguarding
on a full revolution clutch press?
A. Yes, a Type B gate or movable barrier device which permits
manual feeding on the upstroke or when the slide
has stopped on top is an acceptable safeguard.
- Q. If a Type B gate is used as a means of safeguarding, can a
presence sensing light curtain be used to actuate the Type B gate which subsequently initiates the press to work?
A. Yes, the presence sensing light curtain is then only
actuating the Type B gate (the operator safeguard).
VII. BARRIER GUARDS & OTHER SAFEGUARDS
- Q. Can an interlocked barrier
guard be installed on a press for protection of an operator manually feeding
strip stock through openings in the side or through the movable section of the interlocked
barrier guard? (29 CFR 1910.217(c)(2)(iv), (v), and (vi).
A. Yes, this form of guard may be used; however, the hinged or movable section must
be interlocked and can only be opened for clearing a jam or piece of scrap or die changing when the
machine has stopped. In addition, all openings in barrier guards must comply with Table 0-10.
- Q. Does the use of hand
tools for feeding qualify as a "hands out of dies" operation?
A. Yes
- Q. Is compliance with
paragraphs (b)(13) and (b)(14) required when hand tools are used for feeding? 29
CFR 1910.217(c)(4) and (5).
A. No, because in this situation, it is a no hands in die operation.
- Q. If presses are
operated with "hands out of dies" feeding methods, must safeguarding
be provided?
A. Yes
- Q. Why
A. The "hands out of dies" requirement can only be achieved when some
form of operator safeguarding is utilized. Hand tool
feeding, while qualifying as a "hands out of dies" procedure, along
with the sliding bolster feeding method, in and of themselves, do not ensure that the operator can not get his hands in the die.
These approaches should be used in with other safety devices; e.g. two-hand trip, Type A and B gates, presence sensing,
etc.
- Q. On presses operated
as a "hands out of dies" for feeding must the applicable construction
requirements of paragraph (b)?
A. Yes, "hands out of dies operations" has no effect on employers'
obligations to comply with the 29 CFR 1910.217 standards,
except for the brake monitoring and control reliability requirements at 29
CFR 1910.217(c)(5), (b)(13), and (b)(14).
- Q. Why are tools
required for removal of scrap or stuck work pieces when hand feeding is allowed?
A. Removal and clearing operations are not considered to be as technically
difficult as the feeding of dies. The requirement
will reduce the number of times that the operator's hands are in the dies and
represents a compromise with the former
rule for no hands in dies at all times.
- Q. Do the requirements
for testing of clutch/brake mechanism, anti-repeat feature, and single stroke
mechanism apply to
those presses operated in single stroke with "hands in dies" feeding
only?
A. 29 CFR 1910.217(e)(1)(ii) requires weekly inspections and testing of these mechanisms
and features on all presses except those
part revolution presses which comply with paragraphs (b)(13) and (b)(14),
control reliability and brake.
- Q. If a sliding bolster
is used to feed parts, are two-hand controls required to meet the safety
distance requirements?
A. Yes
VIII. SAFETY
DISTANCE
- Q. Where is
the safety distance measurement taken from? The die or the edge of the bolster
or slide?
A. The safety distance is measured from the point of operation of the die (a
recognized hazard). The die dimensions may be
less than or greater than the size of the slide or bolster.
- Q. There are
different formulas for calculating the safety distance on part revolution clutch
machines using two hand control
and full revolution clutch machines using two hand trips. What is the
significance of the sub letters Ds, Dm, Ts, and
Tm?
A. Different sub letters are used to aid users in recognizing that two separate
formulas are used for calculating safety distance
depending on the type of clutch.
- Q. When the
safety distance is calculated using the formulas, what amount of supplemental
distance (margin) is required to
determine the point at which controls or trips must be located?
A. None; however, it is expected that an additional (margin) distance will be added
to allow for some brake stopping time deterioration or slide stopping point tolerance.
- Q. What is
"safety distance"? What is "separation"? Are they the same?
A. "Safety distance" is a proper distance from the controls to the point
of operation, as defined in ANSI B11.1-1982, -1988, and the 1994 ANSI draft proposal of April 24, 1994. "Separation"
is the term used in ANSI B11.1-1982, -1988,
and the April 24,1994 draft revision, which compares with the term
"separation" OSHA used to refer to the distance between an operator's hand controls to require the use of both hands to operate
the press.
- Q. What is meant by
separation when describing the position or arrangement to two-hand trips and
two-hand controls?
A. OSHA recognized the use of "separation distance" when applied to
locating two-hand control buttons remote from each other to discourage attempts at one-hand actuation.
- Q. What is the source of
the 63" hand speed constant?
A. European studies by Dr. O. Lobl of Sweden determined a safety distance for use
in the regulation of foreign countries.
- Q. Which formula is
proper for finding the safety distance on a part revolution clutch press with
two-hand controls? 29 CFR 1910.217(c)(3)(vii)(c)
A. No formula for calculating safety distance on a part revolution clutch press
actuated by a two-hand trip is provided. The
time recommended would be that for the die closing stroke.
- Q. Why is the position
of approximately 90 degrees of crankshaft rotation chosen for determining brake
stopping time?
A. The longest possible stopping time should be used when calculating the safety
distance. The point in the stroke near point
of maximum speed or half way down was considered to be the best place to measure
the longest time for stopping the
slide. This conclusion is currently being challenged based on testing by several
people.
IX. RECORD KEEPING
- Q. How long must the
records required by Section 29 CFR 1910.217(e) be kept?
A. Section 1910.217(e) makes no provision for record retention period.
- Q. Are Federal agencies required
to report injuries to press operators?
A. No
- Q. Must a written record be kept
of pull-out adjustment and testing for each shift change, operator change, or
new die set-up? 29 CFR 1910.217(c)(3)(iv)(d)
A. Yes. The record keeping requirements of 29 CFR 1910.217(e) are applicable.
- Q. If an employee is injured by a
broken piece/part thrown from the die, must a report be sent to the OSHA
Directorate of Safety Standards?
A. No, only injuries to employees which occur within the point of operation are
required to be reported.
- Q. Where did the weekly period for
inspections come from?
A. ANSI B11.1 - 1971 explanatory column accompanying requirements for inspections.
- Q. What periods are recommended by the ANSI
B11.1 - 1997 for press inspections?
A. B11.1 -
1971 recommends weekly, monthly, or possibly longer periods for press and
safeguarding inspections, testing, and
maintenance.
- Q. Are records required to be kept?
A. Yes, B11.1
requires records of inspections.
- Q. For how long?
A. No definite
retention periods are prescribed by OSHA or ANSI for power press records.
- Q. Are periodic inspections and records required for
all presses even when operated on continuous or with no hands or dies?
A. Yes, every
press is required to be inspected and maintained to protect the safety of
operators, die setters, and others.
- Q. Is is necessary to report minor injuries
such as a scratch or pinched finger when feeding a die?
A. No,
only report those injuries which qualify for listing on the OSHA Form 200.
X. MINIMUM REQUIREMENTS FOR POWER PRESS OPERATORS TRAINING
The operators of mechanical power presses must be trained in all phases of
the operation of the equipment and its capabilities and limitations, and;
- All press controls and how to use them;
- The safety guards and devices incorporated on the machines and the correct
use of each;
- The use of tools for removing stuck work and the use of swabs, brushes, or
oil cans for lubricating dies and stock;
- Understanding why, when, and how to use personal protective equipment,
such as safety glasses, gloves, safety shoes, and hearing protections;
- The storage of parts, tools, or other objects on dies, die sets, bolster
plates, or press components not designed to retain them; present hazards of falling on operators; and possible pinch points with moving components.
Operators must be aware of these hazards, as well as the basic housekeeping around the press areas;
- Not to operate the press until the press has been checked and tested
several times prior to production operations. He/she should report any problems which he/she observes to the proper person; and
- Employees who are going to operate presses should receive a minimum of 8
hours on-the-job training under supervision prior to being assigned to operate the press. This could be up to 2 weeks or more,
depending on the complexities of the operation.
XI. MINIMUM TRAINING REQUIREMENTS FOR PRESSROOM SUPERVISORS
- The foreperson must be informed of his/her accountability to the employer
and the employees who work with him/her.
- He/she must know the hazards of power press operations and their set-up
and maintenance.
- The pressroom foreperson must be knowledgeable about the intended function
of the safety guards and devices, and the correct adjustments and uses of each.
- He/she must check each set-up and be sure that all operators are
instructed in safe power press operations before they start work.
- It is his/her responsibility to ensure that correct operating procedures
are being followed.
- The foreperson must see that all maintenance is performed and that presses
are in safe repair prior to their operation. As the employer's representative, the pressroom supervisor is responsible for the
training and operations of the employees under his/her control.
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