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This article is meant
to discuss what’s going on concerning your options for a Cleanroom
System concerning structure – existing walls and ceiling, building
hung system or which type of a variety of floor loaded frame structures.
Comment
1. A modular cleanroom system means you have a floor loaded system you
can move.
Fact – ½ right. Modular means you can move the majority of
the materials of construction. A frame is necessary only if the facility
roof and beam structure cannot support the weight of your cleanroom ceiling,
filters, lights and possibly a portion or all of the mechanical system.
The more filters you put in a ceiling, the more weight you have and the
greater the likelihood that a floor loaded frame will be required.
In California –
we have had two major structural building requirements amendments to the
seismic earthquake zone 4 requirements in the last 15 years or so. The
first one come after the Northern California Loma Prieta quake in “89”
and the second upgrade came after the Southern California Northridge quake
of “95”. Both revisions toughened standards for building lateral
bracing and support. Utilizing an existing structure to support any significant
increase in weight on a non-upgraded older industrial building is not
recommended. First you would trigger a very expensive lateral and support
upgrade program. Second you probably would be required to do the whole
building – not just above the cleanroom. Now-an exception to this
is when you are trying to install Class 10,000 or 100,000 (ISO 6 or8)
the weight load of the filters is not huge. You should get a structural
engineer to calc whether you can do it without problems.
In many instances
we can retrofit an existing room with special wall finishes, upgraded
ceilings, return air chimneys, fan filter units, upgraded lights, custom
entrances and avoid much of the costs of modular rooms – structure
and hardwalls etc. This can still be written off as equipment, or so our
accountant tells us. However – if you need a frame system, this
is surely modular equipment with a 7 year write off. But how about choosing
the right frame? How a manufacturer saves money on manufacturing and cuts
corners is by using the wall system as a frame in the cleanroom design.
Well that’s O.K. if you never want to expand or modify. But half
the reason to go modular is flexibility, especially if you ever want to
move the cleanroom. I will guarantee you’ll want to modify the layout
if you move you can’t do it if the walls are holding up the ceiling.
So you need a floor
loaded frame that the walls integrate under. A good frame has large spans,
tight finish, excellent lateral bracing, rigidity, the ability to support
HVAC equipment and process stuff. Also – expandability – preset
to add to the cleanroom in the X or Y direction. Z (going up) can be accomplished
by lifting ceiling and putting in taller posts. Good design. Cost, above
$25.00 sq. ft. – when you compare bids – notice who includes
an independent frame system and who doesn’t. Tell your bidders what
you want.
Question
2. What kind of spans can I expect my modular frame to handle?
Answer –Depends on weight and height of frame.
The taller you go the more lateral bracing you need and the heavier you
are, the more deflection your frame will experience.
Good frame systems
generally span up to 22’ between posts. This works out great for
return air chimneys – any wider than that is too far apart. You’re
air tends to split and fractionize.
Wider spans are available
as needed, however – we can put chimneys anywhere.
Question
3. How does the frame anchor to the floor?
A. CRS base plates are welded to the steel upright posts. Every effort
is made to direct these plates (6” x 6” or 8” x 8”)
away from traffic areas. Generally they are buried inside return air walls
or return air chimneys. These plates are attached to your concrete floor
with special pre-drilled red head expansion fasteners. This step is generally
inspected by municipalities as part of permitting buy off process. Exposed
plates in rooms should be covered and color marked for safety or recessed
into concrete.
Question
4. Should frames be painted the same as the cleanroom?
Answer – Any steel or metal exposed to the cleanroom
air (whether in the room, return air or supply air) must be finished with
a cleanroom polyurethane or powder paint. Frames above the cleanroom used
for structure only may be painted with an industrial finish.
Question
5. Frames are expensive to ship?
Answer – Yep – but if you break em down so
they stack and fit tight – it’s cheaper and easier.
Question
6. What about using foam walls clad with laminate both sides and aluminum
extrusion uprights every 4’ with a corrugated metal cap as the structure?
(like portable modular offices)
Answer – This is still a modular system and works really well if
you don’t plan on expanding by re-moving walls. We can add to the
facility and add doors and bulk heads and walk thru to existing walls.
We recommend this system with wide flange, hung, gasket t-bar as a low
cost cleanroom up to Class 1,000 generally. This is size, weight and application
dependent. In many instances we integrated a post and I beam frame into
this design to try to get the best of all worlds.
Comment
Please review the drawings included and call with questions.
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