A. Purpose: To establish enforcement policies, inspection procedures,
and performance guideline criteria for the safe design, construction,
installation, testing, maintenance, and use of slide-locks used
for the control of hazardous energy on machinery.
B. Background: Where it is necessary to place hands or other body parts into hazardous
machine areas for servicing and maintenance purposes, practices
and procedures are necessary to disable the machinery and control
the hazardous energy source(s) while the work is being performed.
The lockout/tagout standard requires, in part, machine shutdown
and isolation, which includes the application of energy isolating
devices (EID), defined by §1910.147(b) as a "… mechanical device
that physically prevents the transmission or release of energy…".
In particular, the OSHA standard for Mechanical power-presses,
29 CFR §1910.217(d)(9)(iv), requires employers to provide and
enforce the use of safety blocks whenever dies are being adjusted
or repaired in the press. A safety block is, "… a prop that,
when inserted between the upper and lower dies or between the
bolster plate and the face of the slide, prevents the slide from
falling of its own deadweight" as defined by §1910.211(d)(48).
Another type of EID used for power-press energy isolation is the slide-lock. A
slide-lock device is a positive mechanical engaging device
- i.e., a lock or block - that is capable of preventing the slide
from closing of its own deadweight. [See the Slide-lock device
definition in the Appendix and in the MIOSHA Hydraulic Power-presses
regulation -- R 408.12311, Rule 2311(5)]. On December 21, 1998,
OSHA issued an interpretation letter to General Motors which stated
that slide-locks would not meet the mechanical power-press safety
requirements contained in §1910.217(d)(9)(iv), and suggested that
the use of slide-locks in place of safety blocks on mechanical
power-presses was more appropriately addressed by a variance application.
Since that time, OSHA has received variance applications for slide-locks
as well as requests for additional guidance. This directive cancels
the 1998 letter and establishes new policy concerning the use
of slide-locks.
Safety blocks, slide-locks, locking pins or other mechanisms that physically prevent (block)
the transmission of energy are energy isolating devices. As such,
these isolating devices must be used in accordance with the requirements
set forth in the Control of hazardous energy (lockout/tagout),
§1910.147, standard. Slide-locks as well as safety blocks are
usually designed and intended to address gravity hazards (deadweight
or static forces) associated with the press slide and are not
usually designed to withstand dynamic forces, such as a powered
stroke of the slide. Therefore, it is imperative to prevent machine
energization in cases where these dynamic forces expose employees
to uncontrolled hazardous energy (such as unexpected press activation
caused by human error).
Additionally, the American National Standards Institute recognizes, in their
Safety Requirements for Mechanical Power-presses, ANSI B11.1
- 2001 and Performance Criteria for Safeguarding, ANSI B11.19
- 2003 standards, that safety blocks and other die/slide support
means are designed to restrict hazardous motion but that their
design and construction must not create a hazard to individuals
due to broken or damaged machine components.
To assist employers in providing a safe workplace for employees using mechanical equipment,
OSHA has reevaluated the use of slide-locks as energy isolating
devices when used on mechanical power-presses (in place of safety
blocks) and when used on other general machinery. This directive's
appendix contains the Performance Guideline Criteria for Slide-locks,
which includes design criteria addressing safety factor design.
Compliance officers shall use the guidance material contained
in this directive when evaluating the adequacy of slide-lock use
as energy isolating devices.
C. Action:
- The Chief, MOSH Compliance Services, shall ensure that compliance personnel
are trained in this Instruction.
- Compliance and Consultation Supervisors shall ensure that all compliance officers
attend training.
- The Assistant Commissioner or authorized representative shall ensure compliance
with the attached guidelines for enforcement.
- The Chief, MOSH Compliance Services, shall ensure that the policy and procedures
contained in the Attachment to this
Instruction are followed when conducting inspections where slide-locks
are in use.
Roger Campbell, Assistant Commissioner, MOSH
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Enforcement Policies and Procedures
A. Compliance Officer Safety. As a matter of policy, MOSH prohibits routine
exposure of Compliance Safety and Health Officers (CSHOs) to hazards
associated with the release of hazardous energy. Facility work
areas involved in the inspection must be evaluated by the CSHO
before entering such areas to determine whether there are any
potential hazardous energy exposures.
CSHOs must take reasonable measures to avoid, diminish, or control exposure to hazardous
energy when performing inspection activities. Exposure may be
avoided by such inspection techniques as: 1) interviewing employees
or management representatives in a safe location, 2) photographing
from a safe location, and 3) using engineering or similar drawings
in lieu of obtaining direct measurements. No CSHO may endanger
him or herself at any time and appropriate precautionary measures
must be taken based upon site evaluations and CSHO training. Conversely,
CSHOs must avoid placing themselves in the danger zones
of any machines or equipment if any practices or procedures are
in use that are not compliant with the lockout/tagout standard.
NOTE: The Selection and use of work practices, §1910.333, applies to work on or
near exposed energized parts when CSHOs are close enough to expose
themselves to an electrical hazard. CSHOs may not approach any
electric circuits or equipment unless they have received the electrical
safety-related work practice training prescribed in §1910.332,
and have determined that OSHA???? and the employer have complied
with the requirements of §1910.333.
B. Inspection Guidance. Section 1910.217(d)(9)(iv) requires the use of safety
blocks during the die-setting process on mechanical power-presses
to protect employees from the potential mechanical energy hazards
associated with the working area of a power-press. Employers who
provide and enforce the use of slide-locks that meet the performance
guidance criteria contained in this instruction will be considered
as meeting the Energy isolating device definition in the
lockout/tagout standard with respect to the 1910.217(d)(9)(iv)
safety block provision, and will be considered as meeting the
Energy isolating device definition in the lockout/tagout standard.
The following inspection guidance, together with the criteria contained in the Appendix,
shall be used in evaluating slide-lock design, construction, installation,
testing, use and maintenance for the purpose of determining whether
slide-locks provide a level of protection equivalent level to safety blocks:
- Scope and Application. This instruction provides guidelines on slide-locks that are
used on mechanical and hydraulic power-presses in general industry.
Slide-locks may be used on other types of machinery. In rare
cases, non-interlocked manual type slide locks may be used.
The performance guideline criteria contained in this instruction
may or may not be applicable to those types of slide-locks.
Where slide-locks are used on machines other than hydraulic
and mechanical power-presses, or where manual type slide-locks
are used, compliance officers should apply appropriate reference
material, such as the original equipment manufacturer (OEM)
specifications/instructions and any applicable parts of this
instruction, to determine whether slide-locks are being utilized
in accordance with recognized good engineering practice for that particular piece of equipment.
Also, the Control of hazardous energy (lockout/tagout),
§1910.147, standard applies to the use of slide-locks because
they are energy isolating devices. Slide-locks are mechanical
blocking devices that protect workers from hazardous (mechanical)
energy while they are performing servicing and maintenance work,
such as die set-up, adjustment, cleaning, or repair.
- Employer and Equipment Manufacturer Responsibility. The employer (owner/operator)
is responsible for the proper installation, inspection, testing,
maintenance and use of machine slide-lock systems. CSHOs generally
should not cite an employer for slide-lock design and construction
deficiencies if they exercised reasonable diligence to have
the slide-lock system designed, constructed, and installed in
accordance with recognized good engineering practice, such as
the performance guideline criteria contained in the Appendix.
CSHOs may, however, cite employers when an employer has not
exercised reasonable diligence and/or his or her slide-lock
system presents a serious safety hazard. Refer to Section C.
Citation Guidance for citation policy.
Where employers delegate their responsibility, such as for slide-lock
maintenance, to OEMs or contracted engineering firms the employer
still has an obligation to monitor and ensure that the outside
personnel's actions are adequate to meet the OSHA requirements
and recognized good engineering practices. OEMs, architects,
engineering firms and other entities should produce a slide-lock
system in accordance with recognized good engineering practice
so that the isolating device effectively and reliably controls
the hazardous energy associated with the machine. Failure to
do so may create hazardous conditions through inadequate slide-lock
design, construction or installation. However, CSHOs generally
shall not cite these entities for slide-lock system design,
construction, and installation issues, except if the entities
had employees on site and exposed to a hazard. It is the ultimate
responsibility of the employer using slide-lock devices to exercise
reasonable diligence to discover hazardous conditions and to
take steps to protect its employees.
- Evaluations of Compliance. Compliance with this instruction shall in
no case replace compliance with any relevant OSHA standard,
such as § 1910.147 or 1910.217. Evaluations shall be conducted
whenever slide-lock use is discovered during inspection activities.
- Minor Servicing Exception. When evaluating slide-locks in accordance with
lockout/tagout requirements, CSHOs must determine whether the
employer's work activity meets the minor servicing exception.
See the 29 CFR §1910.147(a)(2)(ii) note. The lockout/tagout
(LOTO) standard is not intended to cover certain minor servicing
activities which are necessary to carry out the production process,
provided that all of the criteria detailed in the exception
are met. Minor tool changes and adjustments, and other minor
servicing operations which take place during normal production
operations, are not covered by this standard if they are routine,
repetitive, and integral to the use of machines or equipment
for production, and if work is performed using alternative protective
measures that provide effective employee protection.
LOTO is not required when each of these elements exists and
employees may perform servicing and maintenance activities with
the machine or equipment energized.
Nonetheless, the exclusion from LOTO does not mean that the
employer can avoid providing employee protection even though
employees carry out these minor servicing tasks with the machine
or equipment energized. Rather, in order to take advantage of
the limited exception, an employer must provide effective
alternative protection instead of lockout/tagout.
NOTE: The previously referenced national consensus standards for machine tools
(ANSI B11.1-2001 and ANSI B11.19-2003) permit control-circuit
means, such as interlocked safety blocks, to prevent actuation
of hazardous (dynamic) motion. Regardless, electrical interlocks
and other control circuits may not be used exclusively to
control hazardous energy during servicing and maintenance
operations covered by OSHA's Control of hazardous energy
(lockout/tagout) standard, §1910.147. Pursuant to §1910.147(b),
control circuits are not, by definition, energy isolating
devices. However, electrical interlocks and other control
circuits, which meet the American National Standards for
Machine Tools, Performance Criteria for Safeguarding (ANSI
B11.19-2003) control reliability provisions, may be used in
conjunction with slide-locks and in lieu of other energy isolation
devices to provide effective alternative employee protection
for servicing and maintenance activities that meet each of
the elements in the lockout/tagout standard's minor servicing
exception, §1910.147(a)(2)(ii)(Note).
In terms of minor press activities, such as minor cleaning,
minor adjustment or minor repair of dies in the press, effective
alternative protection will be considered by OSHA to be provided
if employers meet the electrical performance criteria contained
in Section 4.2 of the Appendix - i.e., if properly applied
control circuits are used in conjunction with other necessary
control measures (e.g., shutting off the press drive motor;
deactivating the clutch/brake mechanism or trip control system;
dissipating residual energy by waiting for the flywheel to
stop; actuating the electro-mechanical slide-lock device that
consists of a control-reliable electrical system or
removing the interlocked safety blocks from the press, and
inserting the safety blocks in the working area of the press
to prevent hazardous slide motion.).
- Documentation. This instruction does not require additional
documentation other than that already required by other standards
-- e.g., energy control (lockout/tagout) procedure documentation,
as required by §1910.147(c)(4). However, in the event that deficiencies
are identified, the CSHO must document the associated hazards
in accordance with established policy.
Additionally, some employers may retain slide-lock design specifications
from the original manufacturer's instructions, training records/certifications
and other documentation regarding slide-lock installation, testing
(both initial and periodic), inspection, use and maintenance.
Where available, these documents should be used by the compliance
officer to determine if the slide-lock program is equally as
effective as safety blocks. Nonetheless, the CSHO shall evaluate
slide-locks in accordance with this instruction, its appendix
and with the specific requirements of the OSHA standards.
The following screening questions provide a general framework
to assist CSHOs in evaluating documentation associated with
a slide-lock:
- Who designed, constructed and installed the slide-locks:
the employer, an OEM, or an engineering contractor? Does the
installer possess adequate expertise to properly design, construct
and install the slide-lock system? Were the slide-locks designed
and constructed in accordance with recognized good practice
and installed as per the manufacturer's instructions?
- b. Did the employer perform a formal hazard analysis (risk
assessment) for foreseeable hazards - e.g., the determination
of the slide-lock's rated load (maximum use) capacity? If
so, does the analysis apply general recognized good engineering
practice, such as the criteria contained in the Appendix?
- Does the slide-lock use a safety factor of at least 2.0
- i.e., based on the maximum anticipated load definition contained
in Section 3.1 of the Appendix? If the employer designed and
installed the slide-locks, how was the safety factor determined
and does it consider reasonably foreseeable dynamic forces?
What information did the employer provide to the designer
and installer of the slide-locks? Is the safety factor legibly
marked on the slide-lock?
- Has anyone modified the slide-locks from the original installation?
An employer who has or has had a slide-lock device modified
from its original design and installation must be capable
of assuring that
the modifications provide a safe level of performance.
- Does the employer have a mechanical integrity program for
the slide-locks? Are the slide-locks inspected and tested
in accordance with Section 8 of the Appendix? Does the employer
perform preventive maintenance? How are defective or damaged
slide-locks identified and removed from service? Who performs
the maintenance and repair of the slide-locks? Who performs
testing of slide-locks?
- Has the employer developed, documented, and implemented
an energy control procedure that includes specific procedural
steps for shutting down, isolating (e.g., applying the slide-lock
isolating device(s); opening the press electric disconnect),
and securing machines to control hazardous energy during servicing
and maintenance activities? Does the energy control procedure
outline the steps to release lockout/tagout as well as the
sequence of action to be taken to test or reposition a press
component so that the employee(s) is protected from the press
point-of-operation hazards?
- Evaluation of Slide-lock Operation. The following considerations
may be used to evaluate slide-lock use:
- Are point-of-operation guards or safety devices used to
complement lockout/tagout to protect employees during machine
testing, machine component repositioning or other activities
such as setting up the press?
NOTE: OSHA's Mechanical power-presses standard, §1910.217
(d)(9)(i), requires employers to develop a procedure that
ensures that an employee is safeguarded from the point-of-operation
hazards during die-setting activities. Thus, a mechanical
power-press die-set procedure would need to clearly and specifically
outline both the point-of-operation safeguarding methods (e.g.,
use of a two-hand control device to position the slide) and
the hazardous energy control (lockout/tagout) steps necessary
to control employee exposure to hazardous areas of the machinery
- i.e., pursuant to the requirements contained in §§ 1910.147(c)(4)
and 1910.217(d)(9), respectively.
Also, the MIOSHA regulation [R 408.112344, Rule 2344(1)] for
hydraulic press slide-lock devices requires point-of-operation
guarding or a device used to protect the operator before the
slide-lock device is in position and secures the press slide.
- On mechanical power-presses, does the employer properly
de-energize the hazardous energy before engaging the slide-lock
- i.e., shut off the press drive motor and its control system;
deactivate the clutch/brake control or trip control system;
wait for the flywheel to stop?
- Is the slide-lock interlocked with the machine control to
prevent actuation of slide motion during work activities -
i.e., for minor servicing tasks that meet the minor servicing
exception contained in the lockout/tagout standard? Are all
electrical control components that actuate and monitor the
slide-lock position designed and installed using a control-reliable
system? See Section 4.2 of the Appendix.
- Are there at least two independent visual means of verifying
slide-lock engagement (i.e., isolation of the mechanical energy
created by the slide)? Some slide-locks can be verified as
engaged by visible means from the slide-lock operation point
(e.g., the slide-lock can clearly be seen as engaged) while
others may use a control-reliable indicator light. In both
cases, a second visual verification must be provided.
- Do employees visually verify that the slide-locks are in
place before accessing the hazardous area? Does the energy
control procedure require the verification of isolation and
de-energization (e.g., pushing a press start button
and visually checking that the disconnect switch handle is
in the off or open position) of other energy sources,
such as electric disconnects?
- On hydraulic power-presses, are electric disconnects used
to isolate the electrical energy source or, in case of the
minor servicing exception, are properly applied electrical
interlocks used as effective protection to prevent
hazardous motion? See the note in Section 4.2.3.1 of the Appendix
for more detail on the coordination of slide-lock use and
the lockout/tagout standard.
- Does each employee performing the servicing and/or maintenance
exercise personal control over the slide-lock and other energy
isolating devices through the application of personal lockout/tagout
devices? See §§ 1910.147(d)(4) and (f)(3) as well as Section
6 of the directive for guidance on personal control criteria.
- Does the slide-lock create any additional hazards, due to
broken or damaged machined components, pinch point, projectile
or ergonomic hazards?
- Training Program Evaluation. A training program must
ensure that employees who use slide-locks (i.e., as an energy
isolating device) are instructed in the safe working procedures
and are qualified to safely perform the functions to which they
are assigned. Employees who implement the energy control procedures
(e.g., when an employee is to use a slide-lock for energy isolation
purposes) or perform the servicing/maintenance activities, are,
by definition, authorized employees. Pursuant to §1910.147(c)(7),
these employees must have the knowledge (e.g., methods and means
necessary for energy isolation) and skills necessary for the
safe application, usage, and removal of the energy controls
-- e.g., how to engage and disengage slide-locks; how to verify
that slide-locks are engaged.
At a minimum, the hazardous energy (lockout/tagout)
control training program must address the following:
- Purpose and function of the energy control program;
- Elements of the energy control procedure relevant to employee duties; and
- Pertinent requirements and the restrictions of the program
applicable to each employee as required by the Control of
hazardous energy (lockout/tagout) standard.
Interviews may be conducted as part of this evaluation to
verify that employee training was provided for slide-locks
and to determine the effectiveness of the lockout/tagout training program.
Furthermore, employees whose job duties require them to inspect,
test or maintain slide-locks must demonstrate the following:
- Knowledge of the employer's performance criteria for the
slide-lock. The Appendix to this directive may be used to
evaluate an employer's performance criteria for slide-locks;
- Knowledge of the employer's mechanical integrity program
for the slide-locks. This includes the types of testing and
inspection required, the frequency of testing and inspection,
and the types and frequency of maintenance required. Further
guidance can be found in Section 8.1 of the Appendix; and
- Experience, education and knowledge that qualifies the employee
to inspect, test and maintain slide-lock systems. Supervisory
employees should have additional qualifications that would
allow them to determine that the testing, inspection, and
maintenance are performed in accordance with good engineering
practice.
- Mechanical Integrity Program. To ensure that all slide-lock
components, auxiliary equipment, and safeguarding are in safe
operating condition and adjustment, employers must have a mechanical
integrity program based on recommendations from the manufacturer,
good engineering practice, and operational experience. Section
8 of the Appendix should be consulted for inspection, testing,
and maintenance criteria.
C. Citation Guidance.
- General. There is no specific requirement for use of
slide-locks in any standard. However, slide-lock devices are
used to control hazardous mechanical energy sources and may
be used as an alternative to safety blocks on mechanical power-presses.
In cases where an employer does not exercise reasonable diligence
in having a slide-lock device designed, constructed, and installed
in accordance with good engineering practice and where the slide-lock
poses a hazard, citations may be issued as follows:
In terms of mechanical power-presses, slide-locks may be used
for energy isolation purposes if their use provides a level
of protection equal to or better than the use of safety blocks.
In this case, the safe use of slide-locks on mechanical power-presses
would be considered meeting the requirements of §1910.217(d)(9)(iv).
Enforcement staff may, however, cite §1910.217(d)(9)(iv) if
an employer's use of a slide-lock device on a mechanical power-press
presents a hazard. In short, employers are required to comply
with the requirements in paragraph (d)(9)(iv) for safety blocks
unless they use slide-locks that are at least as safe as safety blocks.
Furthermore, the Control of hazardous energy (lockout/tagout)
standard, §1910.147, applies to machinery servicing/maintenance
activities, and the lockout/tagout standard may be cited when
the employer's uses of slide-lock devices do not meet the energy
control requirements of the lockout/tagout standard. For example,
§1910.147 (c)(4)(ii)(B) may be cited if the employer does not
clearly and specifically list the procedural steps for shutting
down, isolating (e.g., applying the slide-lock device; locking/tagging
out the electrical disconnect), and securing the machine's hazardous
energy sources. A CSHO shall also cite §1910.147(d)(3) for failure
to adequately isolate the slide on a press.
- Classification of Violations. Any violation that results
in or may result in death or serious physical harm to employees
shall be classified as a serious violation. Energy control program
paperwork deficiencies, on the other hand, shall be addressed
in accordance with current MOSH policy.
APPENDIX
Performance Guideline Criteria for Slide-locks
Foreword
- Automotive Industry Action Group (AIAG)
- Common Configurations
- Pin Lock
- Gear Lock
- Saw Tooth Rack Lock
- Rotating Hammer Head Lock
- Swing Hammer Head Lock
- Other (capable of meeting this guideline)
References
- 29 CFR 1910.147 (LOTO)
- 29 CFR 1910.212
- 29 CFR 1910.217
- ANSI B11.1 - 2001 version
- ANSI B11.2 - 1995 (R 2000) version
- ANSI B11.19 - 2003 version
- ANSI Z244.1-2003
- MIOSHA Hydraulic Power-presses Rule: Slide-lock Device - Section R408.12344 (as
amended Feb. 18, 1997)
1) Purpose: The intent of the criteria is to define the responsibility (supplier
and user) for design, construction, installation, testing, maintenance
and use of slide-locks in hydraulic, mechanical and other power-press
operations when such use is required. This guideline supplements
and is not intended to replace existing OSHA requirements (e.g.
§1910.147, §1910.212, and §1910.217). Rather, it creates criteria
under which slides locks can be used to provide a level of employee
protection that is equal to or greater than that provided by safety blocks.
Note: A slide-lock is an energy-isolating device intended to address gravity hazards,
and it is not usually intended or designed to withstand a powered stroke of the slide.
2) Scope: Any power-press where slide-locks are used with or in lieu of safety blocks.
3) Definitions:
3.1 Control Reliability
3.1.1 The capability of the machine control system, the safeguarding, other control
components and related interfacing to achieve a safe state in
the event of a failure within their safety related functions.
This performance-oriented requirement includes system component/part
redundancy (two processors, two controllers, two concurrently
operating relay circuits, etc,) and performance monitoring/fault
detection features that assure that redundancy is maintained.
Control reliability ensures that the failure of a control system
or device will not result in the loss of the safety-related function(s).
See also the Safety Requirements for Mechanical Power-presses,
ANSI B11.1-2001, Section 8.7 and Annex F - Performance of the safety related functions.
3.2 Maximum Anticipated Load
3.2.1 The maximum anticipated load is normally the static weight of the slide(s),
upper die(s), tooling, and all attachments that apply downward
force due to gravity, but also will include reasonably foreseeable
dynamic forces such as settling inertia.
3.3 Slide-lock
3.3.1. A slide-lock is a mechanical engaging device applied to a power-press, which
shall be designed such that it will support the maximum anticipated load.
3.3.2. The slide-lock
system incorporates an electrical interlocking circuit that prevents
the actuation of hazardous slide motion, when engaged.
3.4 Supplier
3.4.1. Supplier can be the manufacturer, installer, integrator, rebuilder, modifier,
or under certain cases, the user.
3.5 Test
3.5.1 Initial
- Testing performed prior to initial use to validate the control
circuitry and the capability of the slide-lock system to reliably
and effectively hold the maximum anticipated load as defined in
section 3.1 of this section. Testing shall be performed after
any of the following circumstances:
a) Installation
b) Modification to the slide-lock system
c) Significant incident such as exposure to dynamic forces
3.5.2 Periodic - Testing performed as specified by the slide-lock manufacturer
during the preventive/predictive maintenance process as part of
the mechanical integrity program.
4) Design Criteria:
4.1 Mechanical Performance Criteria
4.1.1. The slide-lock device must be secured to the main structure of the press. When
a press has two or more mechanical connections between the slide
and crown, a gear train slide-lock option can be used.
4.1.2. The Safety Factor of the Slide-lock System shall be a minimum of 2.0 based
on the maximum anticipated load. The 2.0 safety factor presumes
the slide-lock system will be designed, constructed, installed,
tested, maintained and used in accordance with all of the performance
criteria in this document.
4.1.3. The slide-lock device shall be designed and installed as not to create an additional
hazard (e.g. pinch point guarding or ergonomics considerations).
4.1.4. The supplier of the Slide-lock System on a power-press shall calculate the
safety factor for the system. The supplier of the slide-lock shall
rate the energy-isolating device at its rated load (maximum use)
capacity so that the user can incorporate the design information
into the machine's hazard analysis (risk assessment). The installer
shall post this information on the press, and the user shall assure
that the information remains on the press in a legible format.
4.2 Electrical Performance Criteria
4.2.1. When the slide-lock system is engaged, it shall be interlocked with the
machine control to prevent actuation of slide motion.
The system shall be designed to enable users to personally secure the system in
the engaged state (typical means of achieving this would be a lockable device).
All electrical control of components actuating and monitoring the slide-lock position
shall be designed and installed using a control-reliable system.
Control-reliable systems achieve a safe state in the event of
a failure within their safety-related function.
4.2.2. Prior to slide-lock engagement on mechanical power-presses, per ANSI B11.1-
2001, the clutch shall be disengaged. The main motor shall be
de-energized (to prevent dynamic loading) in accordance with the
provisions of the 1910.147 standard (LOTO) if machine actuation
and/or dynamic loading present an employee hazard.
Note: Electrical interlocks and other control circuits may not be used exclusively
to control hazardous energy during servicing and maintenance operations
covered by OSHA's Control of hazardous energy (lockout/tagout)
standard, §1910.147. However, electrical interlocks and other
control circuits, which meet the American National Standards
for Machine Tools, Performance Criteria for Safeguarding (ANSI
B11.19-2003) control reliability provisions, may be used in conjunction
with slide-locks and in lieu of other energy isolation devices
to provide effective alternative employee protection for servicing
and maintenance activities that meet each of the elements in the
lockout/tagout standard's minor servicing exception, §1910.147
(a)(2)(ii)(NOTE).
4.2.3 Prior to slide-lock engagement on hydraulic power-presses, per ANSI B11.2-1995 (R2000)
electrical interlocks shall prevent hazardous motion.
4.2.3.1 Dynamic loading shall be prevented through the use of multiple parallel
independent circuits or components with a combination of cross
checking, self-checking, and redundancy. Energy isolation devices
meeting the provisions of the §1910.147 standard (LOTO) also must
be used to prevent hazardous motion after slide-lock engagement,
if machine actuation and/or dynamic loading after slide-lock engagement
would present an employee hazard.
Note: Electrical interlocks and other control circuits may not be used exclusively
to control hazardous energy during servicing and maintenance operations
covered by OSHA's Control of hazardous energy (lockout/tagout)
standard, §1910.147. However, electrical interlocks and other
control circuits, which meet the American National Standards
for Machine Tools, Performance Criteria for Safeguarding (ANSI
B11.19-2003) control reliability provisions, may be used in conjunction
with slide-locks and lieu of other energy isolation devices to
provide effective alternative employee protection for servicing
and maintenance activities that meet each of the elements in the
lockout/tagout standard's minor servicing exception, §1910.147(a)(2)(ii)(NOTE).
4.3 General Design Modifications
4.3.1. The user shall not modify the slide-lock system without prior consultation
with the Slide-lock Manufacturer, or if no longer available, an
entity capable of assuring that any modification provides a level
of performance equal to or greater than the original design.
5) Visual Indication Criteria:
5.1 Visual indication Criteria
5.1.1. When the slide-lock engagement can be visually seen from the slide-lock
operation point, an additional visual verification of the slide-lock
engagement shall be provided by mechanical or electrical control-reliable
means (e.g. indicator light).
5.1.2. When the slide-lock engagement can not be visually seen from a slide-lock
operation point, two independent indications verifying slide-lock
engagement shall be provided by mechanical and/or electrical control-reliable
means (e.g. indicator light).
6) Personal Control Criteria:
6.1 Personal Control Criteria
6.1.1. A slide-lock is an energy-isolating device, used with or in lieu of safety
blocks, that is intended to control gravity hazards. Exclusive
control of other motion causing energy sources, in accordance
with LOTO, can be achieved as described below.
6.1.1.1 When the LOTO standard requires isolation to render hazardous energy sources
inoperative (see 4.2), each exposed employee must use a personal
LOTO device in accordance with the provisions of the LOTO standard.
6.1.1.2 When the servicing activity is minor in nature, routine, repetitive, inherent
to and takes place during normal production operations, an electric
interlock system (see 4.2) may be used to prevent slide motion
if the employee has exclusive control (e.g., use of keyed electrical
switches; lockout of control switches; location and proximity
of control devices) of the interlock system.
7) Installation Criteria:
7.1 Installation criteria
7.1.1. The slide-lock supplier shall provide instructions for the proper installation.
7.1.2. The slide-lock device shall be installed per the supplier's instructions.
7.1.3. Initial startup safety review. The user shall verify that the slide-lock system
was installed per the design and installation instructions.
7.1.4 All installation and verification shall be performed by an individual(s) that has
the training and/or experience necessary to perform these functions
in a manner that assures the safe operation of the slide-lock system.
8) Inspection, Testing, and Maintenance:
8.1 Inspection, testing, and maintenance
8.1.1. The user must conduct initial testing and inspection of the slide-lock
to verify and document the system meets all of the performance
criteria as specified in this guideline.
8.1.2. The slide-lock manufacturer shall establish and document criteria and procedures
for a mechanical integrity program (e.g. preventive maintenance,
predictive maintenance), including the type and frequency of inspections
and periodic testing. Some examples include:
- Visual inspections of mechanical system and components such as gears, pins, bushings,
fasteners, bolts, and gauges;
- Nondestructive examination requirements for safety critical components (e.g., pins);
- Operational inspection and testing (e.g., verification of fault messages; component
functional tests); and
- Electrical diagnostic checks - review manufacturer's recommendations.
8.1.3. The user shall establish, document, and implement a mechanical integrity
program based upon the recommendations of the slide-lock manufacturer,
good engineering practice, prior operating experience, and in
accordance with applicable OSHA provisions (e.g. §1910.217(e)).
8.1.4. All inspection, testing, and maintenance shall be performed or supervised by an
individual(s) that has the training and/or experience necessary
to assure the inspection, testing, and maintenance is performed
in a manner that assures safe operation of the slide-lock system.
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