- Record Type: Interpretation
- Standard Number: 1910.146;1910.147
- Subject: Mechanical equipment,
such as an unguarded agitator, posing a hazard within a
permit space must be locked out or tagged.
- Information Date:1994
March 3, 1994
Mr. Clay Detlefsen, Assistant Director
Environmental & Workers Safety Issues
International Dairy Foods Association
888 Sixteenth Street, N.W.
Washington, D.C. 20006
Dear Mr. Detlefsen:
This is in further response to your
October 6, 1993 letter, requesting an interpretation of the
Control of Hazardous Energy (Lockout/Tagout) standard, 29
CFR 1910.147, with respect to permit space isolation required
by 29 CFR 1910.146.
In your letter you referred to a
dairy plant's confined space program and cleaning of processing
vats and storage tanks. Also, you indicated that the only
hazard within these spaces is a low RPM agitator. Apparently,
the agitator is unguarded and thereby poses potential employee
exposure to hazardous mechanical energy. The permit-required
confined space (PRCS or permit space) standard, 29 CFR 1910.146,
applies to processing vats and storage tanks which are confined
spaces as defined in paragraph (b) and where there is a hazard,
including the agitator as described above. Protection of employees
against unexpected energization of the agitator is also covered
by 1910.147. Under the PRCS program, the permit space must
be isolated as required by 1910.146(d)(3)(ii). Isolation means
the process by which a permit space is removed from service
and completely protected against the release of energy...
by such means as... lockout or tagout of all sources
of energy... As clarified in the 3rd paragraph of the left
hand column on page 4497 of the preamble to the Final Rule
(a copy of which is enclosed for your use), mechanical equipment,
such as an unguarded agitator, posing a hazard within a permit
space must be locked out or tagged in accordance with 1910.147.
With respect to 1910.147, the cleaning
of dairy plant processing vats and storage tanks is considered
to be "servicing and/or maintenance" and not "normal production
operations". The control of hazardous energy (lockout/tagout)
requirements at 1910.147(c) through (f) apply. Please note
that the aforementioned cleaning activities are not considered
minor servicing because they do not take place during normal
production operations.
As noted previously, the permit space
must be isolated by such means as lockout or tagout of all
sources of energy. Use of a control switch locking device
which locks the agitator starter switch in the off position
to isolate control energy may not reliably prevent unexpected
start-up and would not isolate transmission (load) energy
to the agitator. Not only does the control energy have to
be deenergized to prevent unexpected start-up, but also, the
transmission (load) energy must be opened and the energy isolation
device locked out to prevent unexpected energization. Additionally,
although apparently not applicable to deenergizing the agitator,
stored (residual) control energy or transmission energy must
be relieved, disconnected, restrained and otherwise rendered
safe as required by 1910.147(d)(5).
The lockout/tagout standard (1910.147)
is intended to protect employees not only from accidents due
to equipment malfunctions but also inadvertent or intentional
employee acts. For example, an employee may be cleaning a
processing vat or storage tank at the same time that an employee
is performing servicing and maintenance on the transmission
energy part of the agitator's powering system, for example,
at the motor control center as discussed in your letter. Lockout
of the energy isolating device controlling transmission energy
to the agitator would prevent the other employee performing
servicing and maintenance from causing unexpected energization
of the agitator.
Your letter does not include sufficient
information to evaluate whether the control switch locking
device, which locks the machine's starter switch in the off
position, deenergizes the control energy and prevents start-up
by an intentional or unintentional act or by other activation,
for example, because of a failure in the control circuitry.
Generally speaking, a control switch locking device alone
would not meet OSHA's standards as an energy isolating device
because unexpected start- up may be the effect of any of the
aforementioned causes.
We appreciate your interest in employee
safety and health. If we can be of further assistance, please
do not hesitate to contact us.
Sincerely,
H. Berrien Zettler, Deputy Director
Directorate of Compliance Programs
Enclosure
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