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SEMI S22-1103a © SEMI 2003, 2005 5 5.1.14 disconnecting means — a device, or gr oup of de vices, or ot her means b y which the conducto rs of a circuit are intended t o be disconnected fr om their sou rce of suppl y. 5.1…
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4.6 ANSI Standards
5
ANSI/IPC 2221 Generic Standard on Printed Board Design
ANSI/ISA S84.01 Application of Safety Instrumented Systems for the Process Industries
4.7 ISOStandards
6
ISO 13849-1 Safety of Machinery – Safety-related Parts of Control Systems – Part 1: General Principles For
Design
NOTICE: Unless otherwise indicated, all documents cited should be the latest published versions.
5 Terminology
5.1 Definitions
5.1.1 access — a means of approaching or touching.
5.1.2 accessible — having or allowing access, see definition of access.
5.1.3 accredited testing laboratory — an independent organization dedicated to the testing of components, devices,
or systems; competent to perform evaluations based on established safety standards; and recognized by a
government or regulatory body.
5.1.4 ampacity — the current, in amperes, that a conductor can carry continuously under the conditions of use,
without exceeding the design limits for the temperature rating of the insulation, the conductor and the wire
termination.
5.1.5 basic insulation — provides a single layer of protection against electric shock.
5.1.6 bonding (bonded) — the permanent joining of metallic parts to form an electrically conductive path that
ensures electrical continuity and the capacity to conduct safely any current likely to be imposed. See protective
earthing system.
5.1.7 clearance distance — the shortest path between two conductive parts normally carrying current, or between a
conductive part normally carrying current and a conductive part that is connected to the protective earthing system,
measured through air.
5.1.8 Comparative Tracking Index (CTI) — the value obtained in accordance with Method A of IEC 60112 which
determines the Material Group of a printed wiring board. Where the CTI or material group is not known, Material
Group IIIb should be used.
5.1.9 conduit — a part of a closed wiring system of circular or non-circular cross-section for insulated conductors
and/or cables in electrical installations, allowing them to be drawn in and/or replaced.
5.1.10 control device (of a machine) — a device connected into the control circuit and used for controlling the
operation of the machine (e.g. position sensor, manual control switch, relay, magnetically operated valve, etc.).
5.1.11 convenience receptacle — an electrical outlet provided on the equipment, which does not have any load
connected to it during the normal operation of the equipment, but is intended by the equipment manufacturer to be
used to power a piece of maintenance or service equipment.
5.1.12 cord connected equipment — equipment that is intended to be electrically connected to an electric supply by
means of a flexible supply cord and attachment plug.
5.1.13 creepage distance — the shortest path between two conductive parts normally carrying current or between a
conductive part normally carrying current and a conductive part that is bonded to the protective earthing system,
measured along the surface of the insulation.
5 American National Standards Institute, Headquarters: 1819 L Street, NW, Washington, DC 20036, USA. Telephone: 202.293.8020; Fax:
202.293.9287, New York Office: 11 West 42nd Street, New York, NY 10036, USA. Telephone: 212.642.4900; Fax: 212.398.0023, Website:
www.ansi.org
6 International Organization for Standardization, ISO Central Secretariat, 1, rue de Varembé, Case postale 56, CH-1211 Geneva 20, Switzerland.
Telephone: 41.22.749.01.11; Fax: 41.22.733.34.30, Website: /www.iso.ch
SEMI S22-1103a © SEMI 2003, 2005 5
5.1.14 disconnecting means — a device, or group of devices, or other means by which the conductors of a circuit
are intended to be disconnected from their source of supply.
5.1.15 door — a hinged enclosure panel.
5.1.16 double insulation — comprised of both supplementary insulation and basic insulation combined.
5.1.17 duct — an enclosed channel designed expressly for holding and protecting electrical conductors, cables, and
bus bars. Conduits, wireways and under-floor channels are types of ducts.
5.1.18 earthing — see protective earthing system.
5.1.19 electrical enclosure — a panel, compartment, or other defined area housing electrical components used to
enhance the safety of the equipment containing those components.
5.1.20 electrical feed — (referenced from the equipment) a facility supply conductor that provides electrical energy
to a piece of equipment.
NOTE 4: Electrical wiring from enclosure to enclosure, routed through the facility, but provided with the equipment to power
subsystems, are not considered electrical feeds.
5.1.21 energized — electrically connected to a source of voltage.
5.1.22 equipment — a specific piece of machinery, apparatus, process module, or device used to execute an
operation. The term “equipment” does not apply to any product (e.g., substrates, semiconductors).
5.1.23 exposed (as applied to energized parts) — capable of being inadvertently touched or approached nearer than
a safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or insulated.
5.1.24 fail-safe — designed so that a failure does not result in an increased risk.
NOTE 5: For example, a fail-safe temperature limiting device would indicate an out-of-control temperature if it were to fail.
This might interrupt a process, but would be preferable to the device indicating that the temperature is within the control limits,
regardless of the actual temperature, in case of a failure.
5.1.25 Fail-to-safe equipment control system (FECS) — a safety-related programmable system of control circuits
designed and implemented for safety functions in accordance with recognized standards such as ISO 13849-1 (EN
954-1) or IEC 61508, ANSI SP 84. These systems (e.g. safety Programmable Logic Controller (PLC), safety-related
Input and output (I/O) modules) diagnose internal and external faults and react upon detected faults in a controlled
manner in order to bring the equipment to a safe state.
NOTE 6: A FECS is a subsystem to a (PES) Programmable Electronic System as defined in IEC61508 –4.
5.1.26 failure — the termination of the ability to perform an intended function. Failure is an event, as distinguished
from “fault,” which is a state.
5.1.27 fault — the state of an item characterized by the inability to perform its intended function; excludes the
inability to perform required functions during preventive maintenance or other planned actions, or due to lack of
external resources.
5.1.28 fault-tolerant — designed so that a reasonably foreseeable single point failure does not result in an unsafe
condition.
5.1.29 ground fault — an unintentional, electrically conducting connection between an ungrounded or grounded
conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic
raceways, or metallic equipment.
5.1.30 Ground-Fault-Circuit-Interrupter (GFCI) — a device intended for the protection of personnel that functions
to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds a
value in the range of 4 mA to 6 mA (for further information, see UL 943, Standard for Ground-Fault Circuit-
Interrupters).
5.1.31 grounding — see protective earthing system.
5.1.32 hazard — a condition that is a prerequisite to a mishap.
5.1.33 hazardous voltage — voltages greater than 30 Volts RMS, 42.4 Volts peak, or 60 Volts DC.
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5.1.34 hazardous electrical power — power levels equal to or greater than 240VA.
5.1.35 insulation — a layer of non-conductive material used as the outer surface of a conductor for the purpose of
protecting against electric shock.
5.1.36 interlock — a mechanical, electrical or other type of device or system, whose purpose is to prevent or
interrupt the operation of equipment subsystems under specified conditions.
5.1.37 interrupting capacity — the highest current at rated voltage that a device is intended to interrupt.
NOTE 7: Also known as amperes interrupting capacity (AIC).
5.1.38 isolated power system — a power system that has a high impedance between its conductors and the facilities
connection of the equipment. High impedance can be characterized by resistances of one meg-ohm or more.
Isolated power systems are supplied power by isolation transformers or power supplies that have no direct electrical
connection between their primary conductors and their secondary conductors.
NOTE 8: An isolation transformer with one leg of the secondary connected to ground is not an isolated power system.
5.1.39 main disconnecting means — a disconnecting means that is intended to be used to disconnect facilities
electrical power from the system.
5.1.40 maintenance — planned activities intended to keep equipment in proper working order (see also the
definition for service).
5.1.41 material group — a categorization of the Comparative Tracking Index (CTI) of an insulator as follows:
Material Group I: 600 <= CTI
Material Group II: 400 <= CTI < 600
Material Group IIIa: 175 <= CTI < 400
Material Group IIIb: 100 <= CTI < 175
5.1.42 maximum nominal load — the maximum continuous power a circuit will draw under operating conditions
prescribed by the manufacturer. Non-periodic power variations of less than a second in duration are not considered
continuous.
5.1.43 multi-outlet assemblies — assemblies whose primary function is to provide electrical connections and that
have multiple receptacles which are intended for electrical connections.
5.1.44 neutral conductor — an earthed (grounded) AC current carrying conductor.
NOTE 9: It is distinct from protective earthing which is an earthed (grounded) non-current carrying conductor or a non-earthed
(non-grounded) current carrying conductor.
5.1.45 normal operating conditions — the condition of the equipment reasonably foreseen by the manufacturer,
including specified conditions of use, during operation, maintenance and servicing while the equipment is operated,
maintained and serviced according to the manufacturer’s instructions and with no unauthorized equipment
modifications. Normal operating conditions should include consideration of reasonably foreseeable misuse.
5.1.46 operator — a person who interacts with the equipment only to the degree necessary for the equipment to
perform its intended function.
5.1.47 operator access — an area to which, under normal operating conditions, one of the following applies: access
may be gained without the use of a tool, the means of access is deliberately provided to the operator, or the operator
is instructed to enter regardless of whether or not a tool is needed to gain access (if the operator is so instructed, this
area becomes evaluatable as an operator accessible area).
5.1.48 overcurrent — any current in excess of the rated current of the equipment or the rated ampacity (current-
carrying capacity) of the conductor; it may result from overload, short circuit, or ground fault.
5.1.49 overload — operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated
ampacity that, when it persists for a sufficient length of time, would cause damage or dangerous overheating. A
fault, such as a short circuit or ground fault, is not an overload (see short circuit and ground fault).