VAV-107 - page 7

7
Engineering
Specifications
General:
Provide variable volume vaneaxial fans as
shownon thedrawingsof thecapacitiesand
typeas shownon the fan schedule.All fans
shall be licensed to bear the AMCA Certi-
fied Rating Seal for Air Performance and
Sound Power Level. Acceptable vendors
are:ChicagoBlower Corporation.
Housings
:
Fanhousingsare tobeprecisely formedwith
integral rolled flanges on inlet and outlet.
Housingsshall bemechanicallyexpanded to
insure concentricity. Fans 36-1/2" diameter
andsmaller shall bemade fromnot less than
7 ga. thickness metal. Fans 40-1/4" diame-
ter and larger shall bemade fromnot less
than1/4" thickmetal.Housingsshall include
not less than9stationaryguidevanes, inner
fairing, and motor bulkhead to receive a
NEMA ā€œCā€-face, flange mounted, TEAO
electric motor. Motor mounting plates will
vary in thickness, butwill not be less than the
following:
Motor mounting plates will be fabricated so
theboltsholding theC-facemotor arenot in
shear. and if themotor is removed it can be
replaced in the original locationwithout the
useof shims or ancillary centeringdevices.
Rotors:
Fan blades are to be cast from A356-T51
aluminum alloy. Blades shall be airfoil
shaped for maximumefficiency and twisted
fromhub to tip to obtain equal air distribu-
tionalong theblade.Bladeandshankare to
be cast integral to insure maximum blade
integrity. Blade shall have an index mark
cast into the skirt for setting position of
blade.To insurewheel integrity, themethod
of retaining the blade in the hub and the
method for holding the blade at the proper
pitch shall be separate, so theblade retain-
ingmechanism is not affected by blade ad-
justments. Hubs are to be one piece, cast
fromA356-T6 aluminum alloy. Each blade
socket in the hub shall have vernier to be
used in conjunction with blade index mark
foraccuratelysettingangleofattackofblade.
AluminumCastings:
1. Chemical verification of virginmetal shall
be provided. Chemistry of the aluminum
shall be checked during the course of a
heat andadjustmentsmadeasnecessary.
2. Test bars shall be pored at the start and
finishof eachheat.Test barsshall besub-
mitted toaqualified test laboratory for con-
firmation of proper mechanical properties
of castings. Failure of test bars will cause
rejectionof castingsmade fromthat heat.
3. All castings will be visually inspected for
obvious flawsandworkmanship.
4. Since identification of cracks is important
to the integrityof castingsandcrackscan-
not be properly identified by radiographic
inspection, all casting lots shall undergo
sample liquidpenetrant examination.Such
examinationshall bemade inanapproved
laboratory by personnel qualifiedand cer-
tified inaccordancewithSNT-TC-1A(Pro-
cedure Qualification and Certification of
Non-DestructionTesting).Casting lots fail-
ing this inspectionwill be rejected.
5. After castings are penetrant tested, sam-
ples shall be radiographically inspected.
Radiographicsamplesandacceptance/re-
jection criteria shall conform toAluminum
Association Standard AA-CS-M5-85.
Rejection of samples will cause rejection
of entireheat.
ControllablePitch
Assembly:
For decreasedmaintenance, assembly will
include permanently lubricated ball thrust
bearings for eachblade.Compatibilityof turn
down to zero flowshall be requiredwhen in-
dicated. Lossof control signal or de-energiz-
ing fanwill causeblades torotate tominimum
flowposition.
Actuator consists of pneumatic piston with
spring returnmounted integrallyand rotating
with rotor assembly. Supply air is 80 PSI
and is transferred to piston by a rotating
union. Pilot positioner, suitable for 3-15 PSI
control signal, is mounted externally and
feedback signal is provided by cable con-
nection topiston.
AHub
BHub
CHub
3/8"
3/4"
1"
1,2,3,4,5,6 8,9,10,11,12,13,14,15,16
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