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SEMI S2-0703a E © SEMI 1991, 2004 61  Yes  No Comments: 3. Are th ere any threaded conn ections , flange join ts, or special fittings?  Yes  No Comments: 4. If answer to Question 4 is “Yes,” are these connections, jo…

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RELATED INFORMATION 5
SEISMIC PROTECTION
NOTICE: This related information is not an official part of SEMI S2 and was derived from practical application by
task force members. This related information was approved for publication by vote of the responsible committee on
October 21, 1999.
R5-1 Seismic Protection Checklist
Supporting Review Criteria for Seismic Protection of Related Components
If the answer to Questions A.1 or A.2 is “No,” or the answer to any other of these questions in the checklist is
“Yes,” then a detailed analysis may need to be performed by a structural or mechanical engineer.
A. Equipment Anchorage
1. Have lateral force and overturning calculations been performed (see example)?
Yes No Comments:
2. Are all modules fastened at a minimum of four points and can the fasteners support the forces identified in
question 1 above?
Yes No Comments:
3. Is it possible that there could be excessive seismic anchor movements that could result in relative
displacements between points of support or attachment of the components (e.g., between vessels, pipe supports,
main headers, etc.)?
Yes No Comments:
4. Is there inadequate horizontal support?
Yes No Comments:
5. Is there inadequate vertical supports and/or insufficient lateral restraints?
Yes No Comments:
6. Are support fasteners inappropriately secured?
Yes No Comments:
7. Is there inadequate anchorage of attached equipment?
Yes No Comments:
NOTE R5-1: One way of judging whether supports, fasteners, or anchorages are “inadequate” or inappropriately secured” is to
determine whether their stress levels under seismic loading stay below the allowable stress levels set by building code. Such
allowable stress levels are typically a fraction < 1 of the yield strength.
B. Equipment Assembly, Installation and Operation
1. Are the materials of construction of the components susceptible to seismic damage?
Yes No Comments:
2. Are there significant cyclic operational loading conditions that may substantially reduce system fatigue
life?
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Yes No Comments:
3. Are there any threaded connections, flange joints, or special fittings?
Yes No Comments:
4. If answer to Question 4 is “Yes,” are these connections, joints, or special fittings in high stress locations?
Yes No Comments:
5. Are there short or rigid spans that cannot accommodate the relative displacement of the supports (e.g.,
piping spanning between two structural systems)? Is hazardous gas piping provided with a “pigtail” (i.e., spiral) or
bent 3 times (z, y, and z direction) to absorb 3-dimensional displacements?
Yes No Comments:
6. Are there large, unsupported masses (e.g., valves) attached to components?
Yes No Comments:
7. Are there any welded attachments to thin wall components?
Yes No Comments:
8. Could any sensitive equipment (e.g., control valves) be affected ?
Yes No Comments:
C. Seismic Interactions
1. Are there any points where seismically induced interaction with other elements, structures, systems, or
components could damage the components (e.g., impact, falling objects, etc.)?
Yes No Comments:
2. Could there be displacements from inertial effects?
Yes No Comments:
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R5-2 Derivation of Section 19, Seismic Load Guidelines
R5-2.1 The horizontal loadings of 94% and 63%, found in Sections 19.2.1 and 19.2.2, were based on following
assumptions for factors in formula 32-2 in Section 1632.2 of the 1997 Uniform Building Code (UBC):
a
p
= 1.0 (i.e., treat the equipment as a rigid structure)
C
a
= 0.44(1.2) (i.e., seismic zone 4, soil profile type S
D
, and site 5 km from a seismic source type A)
I
p
= 1.0 and 1.5 for non-HPM and HPM equipment, respectively
h
x
/h
r
= 0.5 (i.e., equipment attached at point halfway between grade elevation and roof elevation)
R
p
= 1.5 (i.e., shallow anchor bolts).
Starting with equation 32-2, letting I
p
= 1.5, and substituting the above values:
F
p (ultimate)
= [(1.0 * 0.44(1.2) * 1.5)/ 1.5] [ 1 + 3(0.5)] W
p
= [0.44(1.2)] [ 1 + 1.5] W
p
= [0.528] [ 2.5] W
p
= [1.32] W
p
NOTE R5-2: This number is now adjusted from ultimate strength loading to yield strength loading by dividing by 1.4:
F
p (yield)
= F
p (ultimate)
/ 1.4
= [1.32] / 1.4 W
p
= [0.94] W
p
And for I
p
= 1.0,
F
p
(yield)
= [.94] [ 1.0/1.5] W
p
= [.63] W
p
Notes re selection of a
p
value of 1.0:
Table 16-O of 1997 UBC, line 3.C., was interpreted to read: “Any flexible equipment...”
in structural terms, the structure of typical semiconductor equipment is considered “rigid.”
R5-2.2 Assumptions Used for Above Derivation
R5-2.2.1 Because typical semiconductor equipment is considered rigid, a frequency response analysis was not
considered to be necessary.
R5-2.2.2 Seismic waves typically have vertical as well as horizontal components associated with them; however,
these components typically arrive out of phase (i.e., they do not reach maximum values simultaneously). The
vertical component serves to, in effect, reduce the amount of equipment mass that is available to resist overturning
or toppling. The task force chose to take this into account by limiting the calculated weight available to resist
overturning to 85% of the weight of the equipment. An alternate method, not chosen by the task force, could have
been to simultaneously apply a vertical (Z) force.
R5-3 Source for Examples of Seismic Anchorage Details
R5-3.1 Detailed illustrations of examples of seismic anchorage details were developed by Working Group #9 of the
Japan 300 mm (“J300”) effort, and were printed in their Report No. 9 in the 2nd Lecture, ICs Factory Design for
300 mm Wafer Line Standardizing Study, December, 1996.