DS 7-7R 17-12R Semiconductor Fabrication Facilities ... - FM Global

7-7R
easily removable memory boards. Losses of $15,000 were a daily occurrence in many cities; some of the largest
losses reached in excess of $500,000.
3.7 Uninterruptible Power Supply Overview
Uninterruptible power is accomplished in several ways:
a. Static switches. A static switch is a solid state device which can have 2 to 3 input sources but just
one output. The inputs are typically odd and even feeders, but some switches now come with a third source,
which can be an emergency generator. In this case, the emergency generator should be set to automatically
start upon loss of one switch source.
The output off these static switches would then go to a bus or breaker panel which supplies fab production
tools. If either of the input sources to the switch were lost, the switch digitally transfers to the alternate
input source in less than 1/4 cycle. This is well below the switching time threshold that would affect
production tools (5 to 10 cycles).
This arrangement is best suited for plants with very reliable utility sources from alternate substations.
This arrangement is very good at protecting the production tools from shutting down due to minor power
interruptions (lasting a few seconds), or total loss of power from one utility source. This arrangement does
not protect the facility at all if both utility power sources were lost, unless the three source static switches
are provided, and these are typically used only on critical systems.
b. Diesel no-break systems. This method employs an AC motor driving an AC generator. The generator
in turn supplies the critical loads. There is also a diesel engine connected onto this unit which performs
as the primary driver if utility power were lost. The method used to bridge the time to start the engine
and bring it up to load carrying condition is with the use of internally stored kinetic energy, so the output
of the generator never changes. These systems provide clean continuous, extended power outage protection
which enables the plant to avoid surges and sags in their critical power load. If this type of system
is used, some of the redundancy in the electrical system to this machine can be eliminated, because this
machine can function for long periods of time.
c. Static UPS Modules, with or without emergency generator sets. This is a typical standard UPS system
where an AC source is rectified to DC to power a battery bank. This DC battery power is then inverted
back to an AC source and feeds the fab tools. During normal operations, utility power is fed to the power
supply. If this power is lost, the batteries provide power for the system. The two major drawbacks are
the large physical size of the battery banks needed to supply the power demand of the fab tools and the
limiting time the batteries can supply power. This arrangement provides good protection against power
blips, but battery capacity usually limits the duration of the outage to less than an hour.
d. Hybrid rotary UPS modules, with or without emergency generator sets.
4.0 OTHER APPLICABLE CODES AND STANDARDS
4.1 United States Building Code
REFERENCE DOCUMENT
17-12R SEMICONDUCTOR FABRICATION FACILITIES
Page 28
Building and fire codes are the two basic model codes adopted and enforced by government officials designated
as the ‘‘authority having jurisdiction’’ (AHJ) in the U.S. Three different codes are used in three areas
of the U.S.:
• Northeast: the Building Officials and Code Administrators (BOCA), the National Building Code (NBC) and
National Fire Prevention Code
• Southeast: the Southern Building Code Congress International (SBCCI), the Standard Building Code, and
the Standard Fire Code
• West of the Mississippi River: generally the Uniform Building Code (UBC) and Uniform Fire Code (UFC)
of the International Congress of Building Officials (ICBO).
The electrical code in use in the U.S. is the National Electric Code (NEC), reprinted as NFPA 70, augmented
by NFPA 79, Electrical Standard for Industrial Machinery. Process tools and equipment are typically
reviewed for compliance with NFPA 70, Section 90-7, Examination of Equipment for Safety. Review for
compliance with these codes is typically done by third party firms or by company personnel specifically hired
to validate equipment compliance with company standards.
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