semi合集-English.pdf - 第7069页
SEMI S18-1102 © SEMI 2002 7 8.5.2 The system should be calibrated at intervals specified by the detec ti on system manufacturer. 8.5.3 Cali bration should be pe rformed frequently enough to meet the accuracy criteria. 8.…
SEMI S18-1102 © SEMI 2002
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8 Leak Detection and Alarm Systems
8.1 General
8.1.1 Audible and visual alarms should be provided at
a location where they can be seen and heard by
workers.
8.1.2 Remote audible and visual alarms should be
provided at a constantly attended location so that
appropriate actions can be taken.
8.2 Silane Family Gas Leak Detection Practice
8.2.1 Leak can be detected directly with leak sensors
(gas detectors) or indirectly with heat or fire detectors.
NOTE 14: Sensor types include electrochemical, chemically
treated tape, chemiluminescence, ionization detection, and
UV/IR.
8.2.1.1 Gas detection should be capable of detecting
the silane family gas down to a level at least one-half of
the TLV
®
level.
8.2.1.2 Ultraviolet/Infrared (UV/IR) detectors may be
allowed in some jurisdictions.
8.2.1.3 If UV/IR detection is used, it should be
designed to focus its detection beam across all areas
within the silane family gas exhausted enclosure where
leaks may occur.
8.2.1.3.1 UV/IR detection may be able to detect the
heat signature at levels lower than detectable limits for
gas detectors in some situations.
8.3 Leak Detection Installation
8.3.1 The location of detection points should be
determined by considering airflow patterns, specific
gravity of the gas, surrounding conditions or barriers,
and equipment height.
8.3.2 A leak detection system should be installed with
detection points at intervals appropriate to the detection
technology, or as required by regulation, for exhaust
ducts or cylinder storage.
8.3.3 Leak detectors should also be placed:
• in gas cabinets at locations that will detect leaks
from the piping system or the cylinder,
• in gas manifold boxes for silane family gas
distribution systems, and
• to detect leaks within equipment gas boxes for
equipment using silane family gases.
8.3.4 Leak detectors should be provided or specified
for locations where potential exposure is anticipated
during maintenance or service, when the normal
detection points might not detect a release.
8.3.5 The number and location of detection points
should be determined from detector capabilities, and the
area (or volume) to be monitored by each detector.
NOTE 15: A detection point is a collection opening for a
suction type gas leak detection system or a detector for a
diffusion-type gas-leak detection system.
8.3.5.1 The coverage should be tested after installation
to verify performance.
8.4 Leak Detection Systems Characteristics
8.4.1 Leak detection systems should be fail safe.
8.4.2 Effective detection that can generate warnings
and alarms when a given concentration of gas is
detected.
8.4.3 Warnings, which may not activate the audible
and visual alarms, should be generated at a
concentration level equal to or below OEL or as
specified in an applicable regulation of the country of
use. Alarms, which do activate notifications and audible
and visual alarms, should be activated at OEL
concentration level. If the OEL value is not available
for a silane family gas, or if the value is impractical for
the system, the lowest detectable concentration
technically practical or the concentration set by an
applicable regulation should be used.
8.4.4 The system should be capable of detecting the
target gas beginning at a level at least ½ of the OEL,
and continuing to at least ½ IDLH (Immediately
Dangerous to Life and Health) levels.
8.4.5 A 10% voltage variation should not produce
more than a 30% change in the indicated concentration.
8.4.6 Detection should be capable of detecting a
release, within one minute of exposure of the detection
point, to a leak, which has a concentration above the
concentration of the warning or alarm level.
8.4.7 The alarm should continue, even if the
concentration varies after detection, until it is manually
reset.
8.4.8 Activation of the leak detection system in a gas
cabinet should close the automatic cylinder shut off
valve referenced in Section 14.3.5.
8.5 Maintenance
8.5.1 Gas leak detection and alarm systems should be
periodically inspected and maintained following the
procedures provided by the gas detection system
manufacturer.
8.5.1.1 Inspection and maintenance should be
recorded.
SEMI S18-1102 © SEMI 2002
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8.5.2 The system should be calibrated at intervals
specified by the detection system manufacturer.
8.5.3 Calibration should be performed frequently
enough to meet the accuracy criteria.
8.6 The gas leak detection system should have back up
power (e.g., UPS, emergency power, etc.) to maintain
its function during short-term power interruption or be
fail-safe. The back up power should be periodically
tested or inspected and the test or inspection
documented.
NOTE 16: The testing, the inspection, and the documentation
must be in accordance with any applicable regulations.
8.7 There may be a need for gas detection in some
exhaust treatment systems to detect breakthrough. See
the Exhaust Treatment System section for details.
NOTE 17: Gas detector monitoring in ducts may be required
by regulation or permits.
9 Fire Detection, Suppression, and Alarm
Systems
9.1 Alarms should connect to the facility under the
guidelines of SEMI S2.
9.2 Fire Detection and suppression system(s) where
used should be operational at all times, including when
equipment or facilities are shut down or in maintenance
modes. See SEMI S14 for guidelines for determining
whether such systems are appropriate and for designing
them.
EXCEPTION 1: Maintenance of the fire detection system.
EXCEPTION 2: Activation of the fire detection system
should not remove power from fire detection system and
safety systems.
9.3 Fire Detection and Suppression for Bulk Silane
Systems
9.3.1 An automatic fixed water spray system should be
provided for any bulk silane system for purposes of
cooling the system only.
9.3.1.1 The regulator station and control panel areas
should also be protected by a water spray system for
purposes of cooling the system only.
NOTE 18: Design density, area and duration should be
calculated appropriate to the surface area of the container
using a method such as the one provided in NFPA 318.
9.3.2 Activation of the optical flame detectors, manual
activation, or heat-link activators should initiate the
water spray system and should close emergency shutoff
valves (ESOVs). ESOVs should be located directly on
the source or on the piping, as close to the container as
possible.
9.4 Fire Detection and Suppression
9.4.1 Fires within valve manifold boxes (VMBs) may
impinge on other lines within the VMBs. If this is
assessed as an unacceptable risk, there may be a need
for fire protection.
9.4.2 When fire protection is installed, it should remain
active during all conditions such as maintenance and
service.
EXCEPTION: Maintenance of the fire protection system.
10 Emergency Response
10.1 Exhaust and abatement systems should be left
running during any emergency event, including fire in
the facility.
10.2 Evacuation of Personnel
10.2.1 Procedures for evacuation, as a result of a gas
leak, should be developed based on a hazard analysis
and should be appropriate to the level of hazard.
10.2.2 After an evacuation, no one should re-enter the
area until the exposure risk has been reduced to an
acceptable level.
10.2.3 All personnel in the facility should be trained
regarding proper evacuation procedures.
10.3 Leak Identification and Isolation
10.3.1 If the appropriate method of achieving a safe
situation is for a response team to enter, only authorized
and trained response personnel may enter to locate and
fix the leak.
10.3.2 If the leak location can be accurately
determined, the specific source supplying silane family
gases to the leak location should be automatically shut
down.
10.3.3 If the leak location cannot be accurately
determined, all of the systems supplying the area where
the leak was detected should be shut down.
10.3.4 Do not enclose a silane installation where
adequate exhaust flow can not remain during a leak.
This could lead to an explosion.
10.4 Recovery from Leaks
10.4.1 Trained personnel should investigate the
incident until the original or root cause is determined.
Systems should not be restarted until the safety of the
entire system is confirmed.
10.4.2 Sufficiently purge all affected systems with an
inert gas.
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10.4.3 Perform appropriate leak tests to confirm that
the affected system is safe before allowing silane family
gas back into the system.
10.4.4 Check the reliability of installed detectors.
Change the detectors if necessary.
10.4.5 Confirm that the system (from the silane family
gas, source systems to the gas abatement systems) is not
damaged. Perform corrective actions if necessary.
10.5 Fire and Explosion
10.5.1 The only safe way to extinguish a gas fire is to
shut off the source.
NOTE 19: Do not attempt to extinguish any gas fire except
by shutting off the source. Many countries require fire
extinguishers at gas storage areas, but these should be used
for extinguishing things other than the gas, or for escape.
10.5.2 Water spray or deluge systems should be used
only to cool the container or adjacent containers to
prevent other cylinders from heating or over-
pressurizing.
10.5.3 Accidental extinguishing of a gas fire without
shutting off the gas presents an unacceptable risk of
explosion.
10.5.4 When fire is suspected, contact the emergency
responders.
NOTE 20: Local fire departments may not be trained in
silane family gas fires. The emergency responders should
include plant emergency response teams or public hazard
response teams, as well as fire departments.
10.5.5 Only trained personnel should enter an area
affected by a silane family gas fire.
10.5.5.1 Trained responders to a fire event should be
wearing appropriate protective equipment before
entering the area.
10.5.5.2 After a fire event, check the reliability of
installed fire detectors. Change the detectors if
necessary.
11 Materials, Components, and Constructions
for Silane Family Gas Handling Equipment and
Facilities
11.1 Material Material used for piping and
components for silane family gas should be suitable for
maintaining structural integrity.
11.1.1 Combustible materials (as defined in SEMI S2)
should not be used in constructing assemblies that
contact, support or make up structural components of
silane family gas handling equipment, unless
specifically designed as safety devices.
11.1.2 Materials such as SUS304, SUS316, SUS316L,
Monel, Hastelloy or XM-27 may be needed to provide
adequate protection from corrosion related to
chlorosilanes.
11.1.3 Dust caps for chlorosilanes, plastic gaskets or
O-rings for secondary seals should be made of
chemically stable and heat-resistive materials (e.g.,
PTFE) of a suitable size to fit the cap.
11.2 Components
11.2.1 Components should be nationally approved,
conform to national standards, or be accompanied by
data that demonstrates safety and compatibility.
11.2.2 When cylinder connection gaskets are used they
should be single-use metal-surface compression gaskets
(unless incompatible) that do not provide a source of
additional fuel.
11.2.3 Components used in the piping should be
selected with structures that minimize dead leg sections.
11.2.4 Gas cabinet or equipment suppliers should
provide the user with reliability data for repeated
operations, so the user can schedule replacement of the
components within their expected lifetimes.
11.2.5 If a pneumatic valve is used, the operating gas
should be nitrogen (N
2
) or another inert gas.
11.3 Construction
11.3.1 Equipment, facilities and piping should be
protected from electrostatic discharge.
11.3.2 Assembly of stainless steel components should
be by welding wherever possible to reduce the need for
exhausted enclosures.
11.3.3 Fittings — Fittings should be welded,
(preferably orbital-butt-welded) wherever possible.
Mechanical joints (metal-gasket face-seal fittings)
should be used when disassembly will be required.
NOTE 21: Compression fittings lead to increased risk of
leaks, especially when subjected to expansion and contraction
by temperature changes.
11.3.4 Only cylinder connections approved by a
recognized authority such as the Compressed Gas
Association (CGA) should be used on gas cylinders, to
prevent connection of a cylinder containing an
incompatible gas.
NOTE 22: Special style connections such as CGA-DISS can
provide added protection by their use of “keyed”
differentiation between gas types.
12 Pressurization and Leak Testing
12.1 Each supply piping system should be both
pressure-tested and leak tested.