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BLOWER SILENCERS
Positive Displacement blowers have two impellers that trap a
"pocket" of air eachtime they sweep by the inlet and discharge
connection. A pressure pulse is createdeach time this occurs. This
pressure pulse creates noise and vibration. Blowersilencers can be
used to reduce this noise and vibration.
Silencers are typically used on the inlet and discharge of a
positive displacementblower used for pressure applications. A
discharge silencer is typically used on avacuum application.
There are three basic types of silencers used to reduce the
noise and vibrationgenerated by the pressure pulse.
Chamber Type Chamber Absorptive Type Absorptive Type
Silencer Capacity based on Standard Air Conditions and Silencer
Velocity of 4,600fpm which is equivalent to a 0.2 psi pressure drop
(5.54"H2O). Silencer sizing isbased on a "C" (Pressure Drop
Coefficient) of 4.2. This covers the followingUniversal Silencer
Models:URB,URBY,UCI,UCIY,UCIH,RIS,RISY,RISH,UCD,UCDY,URD,URDY,URDH,SD,SDY,SDH,RD,RDY
AND RDH.
Interpreting the TableThe flows stated under the "INLET
SILENCER" heading would be the flow rating forthe inlet flow to the
blower.
The flows under the "CAPACITY (Inlet CFM 14.7 psia & 68F)"
and "DISCHARGE
SILENCER" heading are calculated back to an inlet flow.
Therefore, if you have ablower with an inlet flow of 500 CFM (Cubic
Feet per Minute) at 6 psig, a 5" inletsilencer would be required
(rated for 639 CFM) and a 4" discharge silencer could beused.
The table can be used as a quick guide to blower silencer sizing
at a reasonablepressure drop. A smaller silencer may be selected,
however, the pressure drop willneed to be calculated. A smaller
silencer will typically lead to an increased pressuredrop through
the silencer. Increased pressure drop results in higher horsepower
forthe blower or vacuum pump.
Size
CAPACITY (Inlet CFM 14.7 psia & 68F)
INLET
SILENCER
DISCHARGE SILENCER
2psig 4 psig6 psig8 psig
10psig
15psig
1 28 30 32 34 36 38 40
1.5 65 71 76 81 84 89 95
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2 107 118 126 133 139 147 156
2.5 153 168 180 190 199 210 222
3 236 259 277 293 307 324 343
3.5 316 347 371 392 410 433 459
4 407 447 478 506 529 558 592
5 639 701 751 794 829 876 929
6 923 1013 1084 1146 1198 1265 1342
8 1598 1754 1877 1985 2074 2191 2324
10 2519 1764 2959 3129 3269 3454 3663
12 3576 3924 4201 4442 4641 4903 5199
14 4323 4743 5078 5369 5611 5927 6285
16 5645 6194 6632 7012 7327 7740 8208
18 7145 7841 8394 8876 9274 9797 10390
20 8880 9745 10433 11031 11527 12176 12913
22 11329 12432 13310 14073 14705 15534 1647324 12844 14094 15089
15954 16671 17610 18676
26 15680 17206 18422 19478 20353 21500 22800
28 18290 20070 21487 22719 23740 25077 26594
30 21099 23153 24789 26210 27387 28930 30680
Est. Temp. 68F 103F 127F 153F 182F 208F 286F
P(H 2O) 5.5 5.5 5.5 5.5 5.5 5.5 5.5
Inlet losses of 0.3 psi and discharge loss of 0.2 psi
assumed
