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SEMI F6-92 © SEMI 19 92 2 4.2 cont rolled work area — A spa c e within a build ing where HPM’s may be s tored, handled, dis pensed, or used. 4.3 equilibr ium vapor concentrati o n (EV C) — The state of a material at whic…

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SEMI F6-92 © SEMI 19921
SEMI F6-92
GUIDE FOR SECONDARY CONTAINMENT OF HAZARDOUS GAS
PIPING SYSTEMS
1 Purpose
To provide a guide for the design, fabrication, and
operation of secondarily contained distribution piping
for hazardous production material (HPM) gases.
2 Scope
This guide covers the general requirements for
hazardous production material distribution piping in
those industries that are included under the H-6
Classification of the Uniform Building Code, or
Articles 51 or 80 of the Uniform Fire Code, or of other
applicable local codes. This guide does not include
requirements for individual exhausted enclosures (e.g.,
valve boxes and gas cabinets).
3 Applicable Documents
3.1 SEMI Documents
SEMI F1 — Specification for Leak Integrity of Toxic
Gas Piping Systems
SEMI F2 — Specification for Seamless Austenitic
Stainless Steel Tubing for Semiconductor
Manufacturing Applications
SEMI F3 — Guide for Welding Stainless Steel Tubing
for Semiconductor Manufacturing Applications
SEMI S2 — Safety Guidelines for Semiconductor
Manufacturing Equipment
SEMI S4 — Safety Guideline for the
Segregation/Separation of Gas Cylinders Contained in
Cabinets
3.2 ANSI/ASME Standard
1
B31.3 — Chemical Plant and Petroleum Refinery
Piping
3.3 Federal Regulations
2
29 CFR — Title 29 of the Code of Federal Regulations
(CFR), Part 1910
49 CFR — Title 49 of the Code of Federal Regulations
(CFR), Chapter I
1 American National Standards Institute, 1430 Broadway, New York,
NY 10018
2 United States Government Printing Office, Washington, D.C. 20402
3.4 ICBO Codes
3
UBC CH 9 — Chapter 9 of the Uniform Building Code,
Requirements for Group H Occupancies
UFC ART 51 — Article 51 of the Uniform Fire Code,
Semiconductor Fabrication Facilities Using Hazardous
Production Materials
UFC STD 79-3 — Standard No. 79-3 of the Uniform
Fire Code
UFC ART 80 — Article 80 of the Uniform Fire Code,
Hazardous Materials
UFC ART 90 — Article 90 of the Uniform Fire Code,
Regulation of Facilities Where Materials Which Are or
May Become Toxic Gases Are Found
3.5 NFPA Standards
4
NFPA 70/ ART 500 — Article 500 of the National
Electrical Code, Hazardous (Classified) Locations
NFPA 497M — Classification of Gases, Vapors and
Dusts for Electrical Equipment in Hazardous
(Classified) Locations
NFPA 704 — Identification of the Fire Hazards of
Materials
3.6 ACGIH Publication
5
TLV
6
— American Conference of Governmental
Industrial Hygienists Threshold Limit Values and
Biological Exposure Indices
4 Terminology
4.1 closed secondary containment — Secondary
containment that has a sealed annulus. In closed
containment systems, the annular space either holds a
certain pressure of gas or a certain level of vacuum. In
closed containment, a change in the pressure or vacuum
would be indicative of a leak in either the primary or
secondary system.
3 International Conference of Building Officials, 5360 South
Workman Mill Road, Whittier, CA 90601
4 National Fire Protection Association, Batterymarch Park, Quincy,
MA 02269
5 American Conference of Governmental Industrial Hygienists, 6500
Glenway Avenue, Building D-7, Cincinnati, OH 45211
6 TLV is a registered trademark of ACGIH.
SEMI F6-92 © SEMI 1992 2
4.2 controlled work area — A spa ce within a building
where HPM’s may be stored, handled, dispensed, or
used.
4.3 equilibrium vapor concentration (EVC) — The
state of a material at which vapor pressure has
stabilized and is no longer rising or falling. The EVC
value (in parts per million) of a material is determined
by multiplying the vapor pressure by 10
6
and dividing
by atmospheric pressure (760 mmHg at sea level).
4.4 hazardous production material (HPM) — A solid,
liquid, or gas that has a degree-of-hazard rating in
health, flammability, or reactivity of Class 3 or 4 as
ranked by NFPA 704 and that is used directly in
research, laboratory, or production processes that have
as their end product materials that are not hazardous.
4.5 highly toxic gas — A chemical that has a median
lethal concentration (LC
50
) in air of 200 parts per
million by volume or less of gas or vapor, or 2
milligrams per liter or less of mist, fume, or dust, when
administered by continuous inhalation for one hour (or
less if death occurs within one hour) to albino rats
weighing between 200 and 300 grams each.
4.6 immediately dangerous to life and health (IDLH)
— A concentration of airborne contaminants, normally
expressed in parts per million or milligrams per cubic
meter, which represents the maximum level from which
one could escape within thirty minutes without any
escape-impairing symptoms or irreversible health
effects. This level is established by the National
Institute of Occupational Safety and Health (NIOSH).
4.7 level of concern (LOC) — Equal to 0.1 of the
IDLH value.
4.8 lower detectable limit of instrument (LDL) — The
lowest concentration of a substance that will give an
instrument response with a signal-to-noise ratio of at
least 3 db.
4.9 material hazard index (MHI) — A numeric value
used for ranking chemical production materials in order
to determine the level of controls necessary for
regulation. MHI is determined by dividing the
equilibrium vapor concentration (EVC) of a material at
25°C by the level of concern (LOC) value for the
material.
4.10 open secondary containment — Secondary
containment with an open-ended annular space. This
annulus must be directed to a system designed to handle
the contained HPM.
4.11 permissible exposure limit (PEL) — The
maximum permitted eight hour time-weighted average
concentration of an airborne contaminant. The
maximum permitted time-weighted average exposures
to be used are those published in 29 CFR 1910.1000.
4.12 pressure decay method — The method of
detection of leakage through pressure loss, over a
period of time, within a vessel or piping system.
4.13 primary containment — The first level of
containment (i.e., the inside portion of the container
that comes into immediate contact on its inner surface
with the material being contained).
4.14 pyrophoric — Capable of spontaneous ignition in
air at or below a temperature of 54.5°C (130°F).
4.15 secondary containment — Level of containment
that is external to and separate from primary
containment. Secondary containment is a method of
safeguarding used to prevent unauthorized releases of
toxic or hazardous gases into uncontrolled work areas.
Secondary containment means those methods or
facilities in addition to the primary containment system.
4.16 threshold limit value/time-weighted average
(TLV/TWA) — As defined by the American Conference
of Governmental Industrial Hygienists (ACGIH).
4.17 uncontrolled work area — Any area outside of a
secondary containment system where people are likely
to be present.
4.18 vacuum decay method — Leakage detection
determined by the loss of vacuum (increase in
pressure), over a period of time within a vessel or
piping system.
5 Containment Function
5.1 Secondary containment should, in case of release,
segregate the hazardous production material (HPM)
from the surrounding area.
5.2 Secondary containment systems should include
provisions to contain and detect substances which pose
health or property hazards and to direct such substances
into areas or facilities that can safely treat, dispose of,
or dilute them prior to release into the atmosphere.
6 Containment Application
Secondary containment may be used on any system if
deemed appropriate by the authority responsible for the
system. Secondary containment should be mandatory
for all HPM’s that are included in the following
categories:
6.1 Those substances with threshold limit values
(TLV) below the lower detectable limit (LDL) of the
detection systems in use.
6.2 Those substances that provide inadequate warning
properties.
SEMI F6-92 © SEMI 19923
6.3 Those substances that fall into the following
categories:
6.3.1 Any HPM’s which have a material hazard index
(MHI) value equal to or greater than 500,000.
6.3.2 Highly toxic gas.
6.3.3 Pyrophorics.
6.3.4 Substances with unknown, but potentially high
toxicities (e.g., organometallics).
6.3.5 Materials with an NFPA 704 reactivity rating of
3 or 4.
6.3.6 Any corrosives that are not contained in inert
process piping.
6.4 Where piping containing HPM ’s is installed in a
manner to conceal it from view.
6.5 Where piping containing HPM ’s is installed in
uncontrolled or unventilated areas such as drop ceilings
or behind walls.
6.6 Where required by UBC H-6 or other existing
codes.
6.7 Where there is any reasonable possibility of a leak
in the primary containment due to normal wear and
tear, possible abuse, or corrosive attack to the piping on
the inside or exterior.
7 Containment Methods
The method of containment may take many forms
provided that the method is sound in engineering
design. This design should be in conformance to
nationally recognized codes and standards as well as to
the requirements of local safety jurisdictions.
8 Materials of Construction
8.1 Chemical Compatibility — If there is a possibility
that the HPM, or its reaction products, is corrosive, to
any extent, to the secondary containment, one should
develop a procedure to verify the integrity of the
containment system. This verification procedure need
only be performed in the event that the HPM, or its
reaction products, contacts the containment (see Section
9).
8.2 Fire Resistance — If walls are used as the
secondary containment system, they should be
constructed of materials resistant of fire. The fire rating
of the secondary containment should be as follows:
8.2.1 Two hour rating for pyrophorics;
8.2.2 One hour rating for all others.
9 Design Requirements
9.1 Design Pressure — The system should be
designed to provide secondary containment with the
ability to withstand the pressure of the entire volume of
the potential leaking source without leakage.
9.1.1 Closed secondary containment systems should
have sufficient design pressure to withstand the
pressure of the entire contents of the source of the
HPM. The design safety factor must be consistent with
ANSI B31.3.
9.1.2 Open secondary containment systems should
have sufficient design pressure to withstand the release
at full tank pressure or the entire contents of the HPM
released within a time of two minutes.
9.1.3 Special consideration should be given to the
containment of pyrophorics. Some pyrophorics can
develop considerable explosive pressure. The
elimination of oxygen from the annulus of a
containment system should be considered in lieu of
explosive pressure data.
9.2 Resistance to External Forces — The method of
construction of secondary containment systems should
be sufficient to withstand:
9.2.1 Normal physical abuse found in the industrial
workplace.
9.2.2 Seismic zone activity as shown in the UBC
(Uniform Building Code) or other applicable codes.
9.3 Leak Integrity — The system should be designed
to provide secondary containment with sufficient leak
integrity to prevent exceeding the PEL of the HPM in
uncontrolled work areas.
9.3.1 Primary piping should be leak tested in
accordance with SEMI F1.
9.3.2 Closed secondary containment systems should
have the same leak integrity as the primary containment
except the closed secondary containment systems
should be leak tested with the annulus pressurized to 2
times the maximum operating pressure with argon
containing at least 10% helium. There should be no
drop in pressure for a period of 12 hours.
9.3.3 Open secondary containment systems should be
leak tested to the same criteria as closed secondary
containment systems per 9.3.2 above.
10 Separation of HPM’s
A single secondary containment may be used to contain
more than one HPM provided that those HPM’s are not
reactive with any other HPM in the common
containment. Documents that should be considered for
proper separation of HPM’s include: