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SEMI S2-0703a E © SEMI 1991, 2004 15 NOTE 41: With the exception of implementation of ground fault protection, shunt trip units that r e quire power to trip (actuate) are not recomm ended to be used in a safety control c…

SEMI S2-0703a

12.3 The emergency off button should be red and

mushroom shaped. A yellow background for the EMO

should be provided.

NOTE 37: Non-lockable self-latching (i.e., twist- or pull-to-

release) EMO buttons may be required by regulations.

12.4 All emergency off buttons should be clearly

labeled as “EMO,” “Emergency Off,” or the equivalent

and should be clearly legible from the viewing location.

The label may appear on the button or on the yellow

background.

12.5 Emergency off buttons should be readily

accessible from operating and regularly scheduled

maintenance locations and appropriately sized to enable

activation by the heel of the palm.

12.5.1 Emergency off buttons should be located or

guarded to minimize accidental activation.

12.5.2 No operation or regularly scheduled

maintenance location should require more than 3 m (10

feet) travel to an EMO button.

12.5.3 The person actuating or inspecting the EMO

button 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.

12.6 See Section 13.5 for additional EMO guidelines

when EMOs are used with UPSs.

13 Electrical Design

13.1 This section covers electrical and electronic

equipment that use hazardous voltages.

13.2 Types of Electrical Work — The following are the

four types of electrical work defined by this guideline:

Type 1 — Equipment is fully deenergized.

Type 2 — Equipment is energized. Energized circuits

are covered or insulated.

NOTE 38: Type 2 work includes tasks where the energized

circuits are or can be measured by placing probes through

suitable openings in the covers or insulators.

Type 3 — Equipment is energized. Energized circuits

are exposed and inadvertent contact with uninsulated

energized parts is possible. Potential exposures are no

greater than 30 volts rms, 42.4 volts peak, 60 volts dc or

240 volt-amps in dry locations.

Type 4 — Equipment is energized. Energized circuits

are exposed and inadvertent contact with uninsulated

energized parts is possible. Potential exposures are

greater than 30 volts rms, 42.4 volts peak, 60 volts dc,

or 240 volt-amps in dry locations. Potential exposures

to radio-frequency currents, whether induced or via

contact, exceed the limits in Table A5-1 of Appendix 5.

13.3 Energized Electrical Work — The supplier should

design the equipment to minimize the need to calibrate,

modify, repair, test, adjust, or maintain equipment

while it is energized, and to minimize work that must

be performed on components near exposed energized

circuits. The supplier should move as many tasks as

practical from category Type 4 to Types 1, 2, or 3.

Routine Type 4 tasks, excluding troubleshooting,

should have specific written instructions in the

maintenance manuals. General safety procedures (e.g.,

wearing appropriate Personal Protective Equipment and

establishing barriers) for troubleshooting, including

Type 4 work, should be provided.

13.4 Electrical Design — Equipment should conform

to the appropriate international, regional, national or

industry product safety requirements.

13.4.1 Nonconductive or grounded conductive physical

barriers should be provided:

 Where it is necessary to reach over, under, or

around, or in close proximity to hazards.

 Where dropped objects could cause shorts or

arcing.

 Where failure of liquid fittings from any part of the

equipment would result in the introduction of

liquid into electrical parts.

 Over the line side of the main disconnect.

 Where maintenance or service tasks on equipment

in dry locations are likely to allow inadvertent

contact with uninsulated energized parts containing

either: potentials greater than 30 volts rms, 42.4

volts peak, or 60 volts dc; or power greater than

240 volt-amps.

NOTE 39: A dry location can be considered to be one that is

not normally subject to dampness or wetness.

NOTE 40: Removable nonconductive and noncombustible

covers are preferred.

13.4.2 Where test probe openings are provided in

barriers, the barriers should be located, and the probe

openings should be sized, to prevent inadvertent contact

with adjacent energized parts, including the energized

parts of the test probes.

13.4.3 Where failure of components and assemblies

could result in a risk of electric shock, fire, or personal

injury, those components and assemblies should be

certified by an accredited testing laboratory and used in

accordance with the manufacturer’s specifications, or

otherwise evaluated to the applicable standard(s).

SEMI S2-0703a

NOTE 41: With the exception of implementation of ground

fault protection, shunt trip units that require power to trip

(actuate) are not recommended to be used in a safety control

circuit, because they are not fail-safe.

13.4.4 Electrical wiring for power circuits, control

circuits, grounding (earthing) and grounded (neutral)

conductors should be color coded according to

appropriate standard(s) per Section 13.4, or labeled for

easy identification at both ends of the wire. Where color

is used for identification, it is acceptable to wrap

conductor ends with appropriate colored tape or

sleeving; the tape or sleeving should be reliably secured

to the conductor.

EXCEPTION 1: Internal wiring on individual

components, e.g., motors, transformers, meters,

solenoid valves, power supplies.

EXCEPTION 2: Flexible cords.

EXCEPTION 3: Nonhazardous voltage multi-conductor

cables (e.g., ribbon cables).

EXCEPTION 4: When proper color is not available for

conductors designed for special application (e.g., high-

temperature conductors used for furnaces and ovens).

13.4.5 Grounding (earthing) conductors and connectors

should be sized to be compatible in current rating with

their associated ungrounded conductors according to

appropriate standard(s) per Section 13.4.

13.4.6 Electrical enclosures should be suitable for the

environment in which they are intended to be used.

13.4.7 Enclosure openings should safeguard against

personnel access to uninsulated energized parts. (Refer

to Appendix 1 for examples of openings for protection

against access from operators.)

13.4.8 Top covers of electrical enclosures should be

designed and constructed to prevent objects from

falling into the enclosures. (Refer to Appendix 1 for

examples of acceptable top enclosure openings.)

13.4.9 The current interrupting capacity (also known as

amperes interrupting capacity, or AIC) of the

equipment main disconnect should be identified in the

facility installation and maintenance manuals.

13.4.10 The equipment should be provided with main

overcurrent protection devices and main disconnect

devices rated for at least 10,000 rms symmetrical

amperes interrupting capacity (AIC).

NOTE 42: Some facilities may require higher AIC ratings

due to electrical distribution system design.

EXCEPTION: Cord- and plug-connected single phase

equipment, rated no greater than 240 volts line-to-

line/150 volts line-to-ground and no greater than 2.4

kVA, may have overcurrent protection devices with

interrupting capacity of at least 5,000 rms symmetrical

amperes interrupting capacity (AIC).

13.4.11 Equipment should be designed to receive

incoming electrical power from the facility to a single

feed location that terminates at the main disconnect

specified in Section 13.4.9. This disconnect, when

opened, should remove all incoming electrical power in

the equipment from the load side of the disconnect. The

disconnect should also have the energy isolation

(“lockout”) capabilities specified in Section 17.

EXCEPTION 1: Equipment with more than one feed

should be provided with provisions for energy isolation

(lockout) for each feed and be marked with the

following text or the equivalent at each disconnect:

“WARNING: Risk of Electric Shock or Burn.

Disconnect all [number of feed locations] sources of

supply prior to servicing.” It is preferred that all of the

disconnects for the equipment be grouped in one

location.

EXCEPTION 2: Multiple units mounted separately

with no shared hazards and without interconnecting

circuits with hazardous voltages, energy levels or other

potentially hazardous conditions may have:

 separate sources of power and separate supply

circuit disconnect means, if they are clearly

identified; or

 separate EMO circuits, if they are clearly

identified.

13.4.12 A permanent nameplate listing the

manufacturer’s name, machine serial number, supply

voltage, phase, frequency and full-load current should

be attached to the equipment where plainly visible after

installation. Where more than one incoming supply

circuit is to be provided, the nameplate should state the

above information for each circuit.

NOTE 43: Additional nameplate information may be

required depending on the location of use.

13.5 Uninterruptable Power Supplies (UPSs) — This

section applies to UPSs with outputs greater than: 30

volts rms, 42.4 volts peak; 60 volts dc; or 240 volt-

amps.

13.5.1 Whenever a UPS is provided with the

equipment, its location and wiring should be clearly

described within the installation and maintenance

manual.

13.5.2 Power from the UPS should be interrupted when

any of the following events occur:

 the emergency off actuator (button) is pushed; or

 the main equipment disconnect is opened; or

SEMI S2-0703a

 the main circuit breaker is opened.

EXCEPTION: Upon EMO activation, the UPS may

supply power to the EMO circuit, safety related

devices, and data/alarm logging computer systems as

described in the exception clauses of Section 12.2.

13.5.3 The UPS may be physically located within the

footprint of the equipment provided that the UPS is

within its own enclosure and is clearly identified.

13.5.4 The UPS should be certified by an accredited

testing laboratory and be suitable for its intended

environment (e.g., damp location, exposure to

corrosives).

13.5.5 The UPS wiring should be identified as “UPS

Supply Output” or equivalent at each termination point

where the UPS wiring can be disconnected.

13.6 Electrical Safety Tests

13.6.1 Equipment connected to the facility branch

circuit with a cord and plug should not exhibit surface

leakage current greater than 3.5 milliampere (mA) as

determined by testing completed in accordance with

“Leakage Current Test for Plug-and-Cord Equipment”

in SEMI S9.

EXCEPTION: Equipment with leakage current

exceeding 3.5 mA is acceptable if documentation is

provided to substantiate that the equipment is fully

compliant with an applicable product safety standard

that explicitly permits a higher leakage current.

13.6.2 Equipment grounding circuits should have a

measured resistance of one-tenth (0.1) ohm or less as

determined by testing in accordance with SEMI S9.

13.7 Equipment in which flammable liquids or gases

are used should be assessed to determine if additional

precautions (e.g., purging) in the electrical design are

necessary.

NOTE 44: NFPA 497 and EN 1127-1 provide methods for

making this assessment.

14 Fire Protection

14.1 Overview — This section applies to fire hazards

that are internal to the equipment.

14.1.1 This section provides minimum safety

considerations for fire protection designs and controls

on the equipment.

14.1.2 This section also provides minimum

considerations for fire detection and suppression

systems when provided with the equipment.

NOTE 45: Detailed guidance on fire risk assessment and

mitigation for semiconductor manufacturing equipment is

provided in SEMI S14.

14.2 Risk Assessment

14.2.1 A documented risk assessment should be

performed or accepted by a party qualified to determine

and evaluate fire hazards and the potential need for

controls. The risk assessment should consider normal

operations and reasonably foreseeable single-point

failures within the equipment. It should not consider

exposure to fire or external ignition sources not within

the specified use environment.

NOTE 46: This risk assessment can be combined with the

overall hazard analysis performed for this guideline, provided

the risk assessor has the required professional expertise to

perform risk assessments for fire hazards. SEMI S7 describes

qualifications for such an assessor.

14.2.2 If an accurate risk assessment depends on the

user’s adherence to specified procedures or conditions

of use, the supplier should describe such procedures or

conditions and state their importance.

14.2.3 SEMI S14 should be used to assess and report

risks to property and the environment.

14.3 Reporting

14.3.1 A summary report should be provided to the

user. The summary should include the following

characterizations, per SEMI S10, for each residual fire

hazard identified:

 the assigned Severity;

 the assigned Likelihood; and

 the resulting Risk Category.

14.3.2 Optional fire risk reduction features should be

described in the pre-purchase information provided to

the user.

14.3.3 The scope and effectiveness of the means of fire

risk reduction should also be identified and reported,

including the expected risk reduction (as described in

Section 14.3.1).

14.3.4 If, due to fire hazards within the equipment,

thermal or non-thermal (e.g., smoke) damage is

possible outside of the equipment, then this possibility

should be reported to the user. This report should

include a qualitative description of the foreseen

scenario.

14.4 Fire Risk Reduction

14.4.1 Materials of Construction — Equipment should

be constructed of noncombustible materials wherever

reasonable. If process chemicals do not permit the use

of noncombustible construction, then the equipment

should be constructed of materials, suitable for the uses

and compatible with the process chemicals used, that

contribute least to the fire risk.