Hazards Analysis Process
This exhibit provides guidance and the rationale for determining if a hazardous energy source(s) is present which
would require lockout/tagout during installation, servicing and maintenance of equipment, machinery or systems.
Once the scope of work is defi
ned, the critical questions that must be answered are
What energy sources are present?
Are they potentially hazardous?
The answer to these questions is the following three
step hazards analysis process used by Controlling Organizations.
Where the h
azards analysis indicates that lockout/tagout is required, see the
Hazardous Energy Isolation
Step One: Review Tasks
Consider all tasks involved with the service and maintenance work. Such work may include setup, installation,
djusting, cleaning, troubleshooting, and programming. Examples of tasks that routinely require
entry into a machine's point of operation or any associated danger zone
repair of electrical circuits
cleaning, repairing and maintain
ing machinery with moving parts
cleaning jammed mechanisms
removing or bypassing a guard or other safety device
work on lines carrying hazardous materials, materials under pressure, or materials at dangerous
temperatures (cold or hot).
working under he
avy equipment or machinery with all or part of it raised and/or capable of falling.
Step Two: Identify Hazards
Evaluate the potential hazard associated with each energy source within the work boundary (electrical,
mechanical, thermal, pneumatic, hydraulic
, radiation, chemical, etc.).
Identify hazards that might arise from the interaction of the release of energy and the work environment. The
following situations provide examples of possible interactions.
work on water lines over electrical components or
electrical systems in wet locations creating a shock
or arc flash hazard
work on compressed air in an area where inadvertent activation might generate toxic or radioactive
dusts or aerosols creating contamination or personal exposure
repair work on overh
ead water or air lines from a ladder that may cause a worker to fall or drop tools if
startled by the impact of the air or water or the elevated noise level from release of compressed air
work on low pressure inert gas line in confined space creates asphy
maintenance that must be done under machinery or equipment that may fall on a worker
work near live steam or pressure relief valves subject to thermal and pneumatic hazards
servicing of equipment in an area with magnetic field that may pr
opel ferrous tools toward the magnet.
Step Three: Assess Potential Consequences
Evaluate whether the hazards identified in step two could harm workers, given the precautions used on the job.
Assume that workers are present when the energy is released and
any interlocks are disabled. The following
table on energy sources provides threshold information useful in making this evaluation. Where a system is
designed for lockout/tagout, there is a good possibility that either the manufacturer or PNNL has evaluat
hazards and determined that lockout/tagout is necessary. Whenever an energy source has the potential to harm
workers, lockout/tagout is required, unless de
energizing the source introduces additional or increased hazards
or is infeasible due to equi
pment design or operational limitations. Such cases require job
such as energized electrical work permits or written lockout/tagout procedures approved by the PNWD
Lockout/Tagout Committee and the Controlling Organization.
Hazards Analysis Process
Form of Ene
Consider Use of Lockout/Tagout Based on
Results of Analysis
Lockout/Tagout is Required*
less than 50 V and less than 1000 W, less than
J stored energy in a capacitor
greater than 50 V and less than 5 mA, less than
10 J stored energy in a capacitor (minimal risk
less than 50 V and greater than 1000 W, less than
10 J stored energy in a capacitor
equal to or greater than 50 V
and equal to or
greater than 5 mA, less than 10 J stored energy in
greater than 10 J stored energy in a capacitor
(moderate/high risk category)
liquids less than 52°C (120°F)
liquids equal to or greater than 52°C (120°F)***
liquids greater than
liquids equal to or less than
equal to or less than 150 psi
greater than 150 psi***
equal to or les
s than 150 psi
greater than 150 psi***
other electromagnetic radiation
class 3B or class 4 lasers**
potential to exceed administrative control level
in short time period
energizing the source by lockout/tagout introduces additional or increased hazards or is infeasible due to
equipment design or operational limitations.
**Many sources of nonionizing electromagnetic radiation involve electrical hazards that must
be considered even
when the radiation emitted is not hazardous.
***Double valve isolation is required when the operating temperature exceeds 200°F or the operating pressure exceeds
500 psig. See
Hazardous Energy Isolation Practices
Supplemental Information on Thresholds for Various Forms of Energy
While the most common energy source is electrical energy, it is critical that the Controlling Organization consider all
forms of energy that may be present. The following information
is provided in support of thresholds where
Hazards Analysis Process
lockout/tagout becomes mandatory. Levels below the thresholds require analysis because they may also cause injury
depending on the work situation.
refers to generated electrical power or static e
lectricity. In the case of generated electricity,
the electrical power can be turned on or turned off. Batteries convert chemical energy to electrical energy that
can be switched on or off. Capacitors store an electrical charge that can only be dissipated
or controlled. Static
electricity cannot be turned off; it can only be dissipated or controlled. Moderate or high risk electrical systems
and equipment require lockout/tagout. The following thresholds apply to electrical energy.
less than 50 V and greater
than 1000 W, less than10 J stored energy in a capacitor
greater or equal to 50 V and greater or equal to 5 mA, less than 10 J stored energy in a capacitor
greater or equal to 10J stored energy in a capacitor.
is manifested by high
or low temperature. This type of energy is the result of mechanical
work, radiation, chemical reaction, or electrical resistance. It cannot be turned off or eliminated; however, it
can be dissipated or controlled. The potential for hot or cold burn injurie
s is dependent on at least two
the temperature of the liquid
the period of contact.
The threshold for burn (scald) injuries from contact with hot liquids is 52°C (120°F).
Typically any freezing of the tissue may cause a cold injury. The thresh
old for cold injuries to tissues is
slightly below freezing (27°F or
3°C). Cryogenic liquids are normally gases at room temperature and
pressure, but are converted into liquids which by definition have boiling points less than
y, they all present a cryogenic burn hazard. Liquid carbon dioxide and nitrous oxide also present
cryogenic burn hazards, even though their boiling points are above
150°C. Contact hazards with hot or cold
surfaces are typically controlled with insulation
the energy of motion) may involve linear travel, rotation or a combination
of the two. This type of energy cannot be turned off or on but may be contained or stopped. No threshold is
proposed for kinetic energy. Ea
ch situation must be evaluated.
the energy of position)
involves the location of an object above a
designated level or the compression of springs. Configurational energy can be minimized by moving an object
lower position. The energy of springs can be dissipated or controlled; it cannot be turned off or on. No
threshold is proposed for potential energy. Each situation must be evaluated.
is the pressure (either above or below atm
ospheric pressure) contained in a
liquid (such as oil or water) or in a gas (such as air). Hydraulic or pneumatic energy may be turned off.
Hydraulic or pneumatic energy also may be stored; in which case, it must be released or dissipated.
Where there is
a potential for deadheading a pneumatic air source against unprotected skin, OSHA considers 30 psi air
or greater to be hazardous because it can penetrate the skin barrier through open wounds or do damage if directed at
body openings. OSHA's limit of 30 ps
i for use of compressed air for cleaning clothes does not protect from particulates
that may be generated by cleaning with pressurized air below 30 psi.
Where the skin and eyes are protected and there is no potential for deadheading the source against the
pressure required for pneumatic jet injuries to healthy unbroken skin is over 600 psi. Pneumatic sources directed at
eyes or ears can cause injuries at significantly lower pressures depending on the proximity and diameter of the jet.
ergy is liquid un
der pressure. The pressure of a
hydraulic jet required to break intact healthy skin is over
600 psi. However, releases of liquids at much lower pressures are hazardous to eyes, ear drums and open wounds
depending on the diameter of the jet
and distance traveled by the fluid before it strikes the affected tissue. Hydraulic
injection injuries have been recorded at distances up to 4 inches between the skin and the source. For water and other
liquids conveyed in larger piping systems, the liqui
d momentum may be sufficient to knock a worker down depending
on the diameter of the pipe and the pressure.
Hazards Analysis Process
Water and compressed air pressures of 150 psig or less exist in nearly every industrial or commercial installation
requiring these utilities. Histor
ical evidence indicates that when using normal PPE (coveralls, gloves and safety
glasses), lockout/tagout is not normally utilized or required for servicing and maintenance of these common utility
water or compressed air systems operating at pressures up t
o 150 psig. Exceptions exist where the water temperature is
over 120°F or the environment of the work activity introduces additional secondary hazards. The absence of injuries
solely due to these common utility pressures during service and maintenance of s
uch systems without lockout/tagout
protection further substantiates that hazardous energy control is not required where secondary hazards do not exist.
Compressed gas cylinders or subsequent valves feeding downstream systems are subject to lockout/tagout w
here 1) the
system is being serviced or modified, AND 2) the gas is flammable, the gas is toxic, or the delivery pressure can
exceed 150 psig with the regulator valve fully open. Lockout/tagout does not apply to cylinder installation and
Due to th
e range of pressures at which different types of hydraulic and pneumatic injuries can occur, each situation
must be evaluated using the following decision tree. This decision tree only applies to non
hazardous gases and
liquids. Hazardous gases and liquids
at any pressure must be locked out due to their chemical hazards (e.g., toxic,
Hazards Analysis Process
is electromagnetic radiation that is a health
hazard over specified maximum
permissible exposure (MPE) levels even though it does not cause ionization of molecules. Nonionizing
radiation includes high intensity visible and invisible light (UV and IR) sources, microwaves, radiofrequency
waves, and mag
netic fields. Where nonionizing radiation sources exceed their respective MPE, the hazard
must be evaluated. Where workers could be exposed to beams from Class 3B and Class 4 lasers while
performing maintenance, lockout/tagout is required if the laser is n
ot powered by cord and plug connection.
: Because a laser must be energized during alignment of Class 3B and Class 4 lasers, a
Laser Use Permit
is used to specify the control measures rather than lockout/tagout.
there is no threshold for sy
stems that may release hazardous chemical solutions at any pressure,
flammable liquids or gases, or any gases that have a potential of creating a hazardous atmosphere. This
includes gases used for fire suppression systems.
: The use of lockout/tagout f
or chemical systems may be
necessary to prevent a release that would have environmental consequences.
When the potential exists for a worker to exceed an administrative control level in a short
time period, consider the use of lockout
/tagout as part of the work planning phase. Situations where
lockout/tagout may apply include: 1) to prevent external radiation exposure during service or maintenance of
generating devices, 2) to prevent external radiation exposure during use of
exposure systems with
sealed sources having pneumatic or mechanical transport systems, 3) to reduce external exposures from
shielded storage areas during maintenance work in the immediate vicinity, and 4) to reduce internal exposures
when energy sources lo
cated inside a contamination area have the potential to create airborne contamination.