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SEMI S2-0703a E © SEMI 1991, 2004 22 installation, an d operating conditions. The need fo r special handling devices and anc hors should be indicated in the instru ctions. Unanchored equ ipment in its installed co nditio…
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17 Hazardous Energy Isolation
17.1 General
17.1.1 Lockable energy isolation capabilities should be
provided for tasks that may result in contact with
hazardous energy sources.
17.1.2 Where service tasks may be safely performed on
subassemblies, energy isolation devices (e.g., circuit
breakers, disconnect switches, manual valves) may be
provided for the subassemblies for use as an alternative
to shutting down the entire equipment system. The
isolation devices should isolate all hazardous energy to
the subassemblies and be capable of being locked in the
position in which the hazardous energy is isolated.
17.1.3 The person actuating or inspecting an energy
isolating device should not be exposed to serious risks
of tripping or falling or of coming in contact with
energized electrical parts, moving machinery, surfaces
or objects operating at high temperatures, or other
hazardous equipment.
NOTE 71: Hazardous energies include electrical, stored
electrical (e.g., capacitors, batteries), chemical,
thermal/cryogenic, stored pressure (e.g., pressurized
containers), suspended weight, stored mechanical (e.g.,
springs), generated pressure (e.g., hydraulics and pneumatics),
and other sources that may lead to the risk of injury.
NOTE 72: In order to minimize down-time and provide ease
of use, it is preferred to have energy isolation devices located
in the areas where maintenance or service is performed.
NOTE 73: Energy isolation devices for incompatible
hazardous energy sources (e.g., electrical and water,
incompatible gases) are recommended to be separated.
NOTE 74: Isolation of hazardous energy may include:
deenergizing of hazardous voltage; stopping flow of
hazardous production material (HPM); containing HPM
reservoirs; depressurizing or containing HPM and pneumatic
lines; deenergizing or totally containing hazardous radiation;
discharging of residual energy in capacitors; stopping of
hazardous moving parts; and shutting off hazardous
temperature sources.
NOTE 75: Energy isolation devices with integral locking
capabilities are preferred, but may not be feasible or
commercially available, in which case detachable lockout
adapters may be used.
NOTE 76: See Section 14 for information on fire protection
hazardous energies.
17.2 Installation and Maintenance Manuals
17.2.1 Installation and maintenance manuals should
identify the types of hazardous energies within the
equipment.
17.2.2 Installation and maintenance manuals should
provide specific instructions for the equipment on how
to:
shut down the equipment in an orderly manner;
locate and operate all the equipment's energy
isolating devices;
affix energy isolating (“lockout/tagout”) devices;
relieve any stored energies;
verify that the equipment has actually been isolated
and deenergized; and
properly release the equipment from its isolated
state.
17.2.3 Where the manufacturer provides written
maintenance procedures for tasks within subassemblies,
and intends that these tasks be performed without
controlling hazardous energies at the entire equipment
level, the installation and maintenance manuals should
provide appropriate energy isolation procedures at the
subassembly level.
17.3 Electrical Energy Isolation
17.3.1 The main energy isolation capabilities
(equipment supply disconnect) should be in a location
that is readily accessible and should be lockable only in
the deenergized position.
NOTE 77: For equipment with multiple incoming supply
sources, it is recommended that all of the energy isolation
devices be located in one area.
17.4 Non-Electrical Energy Isolation
17.4.1 The equipment should include provisions and
procedures so that hazardous energy sources, such as
pressurized systems and stored energy, can be isolated
or reduced to a zero energy state prior to maintenance
or service work.
17.4.2 The hazardous energy isolation devices should
be in a location that is readily accessible.
17.4.3 The hazardous energy isolation devices should
be capable of being locked in the position in which the
hazardous energy is isolated.
18 Mechanical Design
18.1 This section covers hazards due to the mechanical
aspects of the equipment.
NOTE 78: This is similar to the essential requirements of
European Union directives. The supplier has the option of
demonstrating compliance by choosing standards that are
appropriate to the machine and application.
NOTE 79: Pressurized vessels must meet applicable codes
and regulations.
18.2 Machine Stability — Equipment, components,
and fittings should be designed and constructed so that
they are stable under reasonably foreseeable shipping,
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installation, and operating conditions. The need for
special handling devices and anchors should be
indicated in the instructions. Unanchored equipment in
its installed condition should not overbalance when
tilted in any direction to an angle of 10 degrees from its
normal position.
NOTE 80: See IEC 61010-1 for an example of stability tests.
18.3 Break-up During Operation — The various parts
of the equipment and its linkages should be able to
withstand the stresses to which they are subjected when
used as designed. Precautions should be taken to
control risks from falling or flying objects.
18.3.1 The potential effects of fatigue, aging,
corrosion, and abrasion for the intended operating
environment should be considered as part of the
mechanical hazards risk assessment.
18.3.2 Where a risk of rupture or disintegration
remains despite the measures taken (e.g., a substrate
chuck that loses its vacuum), the moving parts should
be mounted and positioned in such a way that, in case
of rupture, their fragments will be contained.
18.3.3 Both rigid and flexible pipes carrying liquids or
gases should be able to withstand the foreseen internal
and external stresses and should be firmly attached or
protected against external stresses and strains. Based on
the application, an appropriate factor of safety should
be included.
18.4 Moving Parts — The moving parts of equipment
should be designed, built, and positioned to avoid
hazards. Where hazards persist, equipment should be
fitted with guards or protective devices that reduce the
likelihood of contact that could lead to injury.
18.4.1 Where the machine is designed to perform
operations under different conditions of use (e.g.,
different speeds or energy supplies), it should be
designed and constructed in such a way that selection
and adjustment of these conditions can be performed
safely.
18.4.2 Selection of Protection Against Hazards Related
to Moving Parts — Guards or protective devices used
to protect against hazards related to moving parts
should be selected on the basis of a risk assessment that
includes the:
hazards that are being guarded against;
probability of occurrence and severity of injury of
each hazard scenario; and
frequency of removal of guards.
18.4.3 Guards and protection devices. Guards should:
reduce the risk that personnel will contact the
mechanical hazard to an acceptable level; and
not give rise to additional risk.
18.5 Lifting Operations — Equipment presenting
hazards due to lifting operations (e.g., falling loads,
collisions, tipping) should be designed and constructed
to reduce the risk to an acceptable level.
18.6 Extreme Temperatures — Surfaces that are
accessible to personnel, and that are at high (per
temperature limits in Table 1) or very cold temperatures
(below -10C [14F]), should be fitted with guards or
designed out.
18.6.1 Where it is not feasible to protect or design out
the exposures to extreme temperature, temperatures
exceeding the limits are permitted, provided that either
of the following conditions is met:
unintentional contact with such a surface is
unlikely; or
the part has a warning indicating that the surface is
at a hazardous temperature.
Table 1 Potentially Hazardous Surface Temperatures
Maximum Surface Temperature, in
C
Accessible Parts
Metal Glass, Porcelain,
Vitreous Material
Plastic,
Rubber
Handles, knobs, grips, etc., held or touched for short periods (5
seconds or less) in normal use.
60 70 85
Handles, knobs, grips, etc. held continuously in normal use. 51 56 60
External surfaces of equipment, or parts inside the equipment,
that may be touched.
65 80 95
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19 Seismic Protection
NOTE 81: Users have facilities located in areas that are
susceptible to seismic activity. The end user may require more
stringent design criteria because of increased site vulnerability
(e.g., local soil conditions and building design may produce
significantly higher accelerations) and local regulatory
requirements. Certified drawings and calculations may be
required in some jurisdictions.
19.1 General — The equipment should be designed to
control the risk of injury to personnel, adverse
environmental impact, equipment and facility damage
due to movement, overturning, or leakage of chemicals
(including liquid splashing), during a seismic event.
The design should also control equipment damage due
to failure of fragile parts (e.g., quartzware, ceramics)
during a seismic event.
NOTE 82: These criteria are intended to accomplish two
things:
(1) allow equipment suppliers to correctly design the
internal frame and components to withstand seismic forces;
and
(2) allow equipment designers to provide end-users with the
information needed to appropriately secure the equipment
within their facility.
19.1.1 Because preventing all damage to equipment
may be impractical, the design should control the
failure of parts that may result in increased hazard (e.g.,
hazardous materials release, fire, projectile).
NOTE 83: It is recommended that the hazard analysis
described in Section 6.8 be used to evaluate both the risk of
part failure and the effectiveness of control measures.
19.1.1.1 These parts should be accessible for
evaluation of damage.
NOTE 84: SEMI S8 contains guidelines for maintainability
and serviceability; these may be used to determine
accessibility.
19.2 Design Loads — The equipment, subassemblies,
and all devices used for anchoring the equipment
should be designed as follows:
19.2.1 For equipment containing hazardous production
materials (HPMs), the equipment should be designed to
withstand a horizontal loading of 94% of the weight of
the equipment, acting at the equipment’s center of
mass.
19.2.2 For equipment not containing hazardous
production materials (HPMs), the equipment should be
designed to withstand a horizontal loading of 63% of
the weight of the equipment, acting at the equipment’s
center of mass.
NOTE 85: Subassemblies may include transformers, vessels,
power supplies, vacuum pumps, monitors, fire suppression
components, or other items of substantial mass that are
attached to the equipment.
19.2.3 Horizontal loads should be calculated
independently on each of the X and Y axes, or on the
axis that produces the largest loads on the anchorage
points.
19.2.4 When calculating for overturning, a maximum
value of 85% of the weight of the equipment should be
used to resist the overturning moment.
NOTE 86: Because equipment may be placed into service
anywhere in the world, it is recommended that the seismic
protection design of the equipment be based upon
requirements that allow the equipment, as designed, to be
installed in most sites worldwide. The above loads are based
on 1997 Uniform Building Code (UBC) requirements for
rigid equipment in Seismic Zone 4, and are assumed to satisfy
most design situations worldwide.
NOTE 87: If the equipment or internal component is flexible
as defined by the UBC, is located above the midheight of the
building, or is within 5 km of a major active fault, the
horizontal design loadings in Sections 19.2.1 and 19.2.2 may
not be conservative. Likewise, there are several conditions for
which the horizontal design loadings are overly conservative
(e.g., rigid equipment with rigid internal components located
at grade, or sites with favorable soils conditions). For these
conditions, designing based on the more detailed approach in
the UBC may result in a more economical design. It is
recommended that the user engage a professional mechanical,
civil, or structural engineer to make these determinations.
19.3 The supplier should provide the following data
and procedures to the user. This information should be
included in the installation instructions as part of the
documentation covered in Section 9.
A drawing of the equipment, its support equipment,
its connections (e.g., ventilation, water, vacuum,
gases) and the anchorage locations identified in
Section 19.4.
The type of feet used and their location on a base
frame plan drawing.
The weight distribution on each foot.
Physical dimensions, including width, length, and
height of each structurally independent module.
Weight and location of the center of mass for each
structurally independent module.
Acceptable locations on the equipment frame for
anchorage.
NOTE 88: A “structurally independent module” reacts to
seismic loads by transferring substantially all of the loads to
its own anchorages, as opposed to transferring the loads to
adjacent modules.