Sizing the Air
Receiver
The air receiver must in general be
sized according
- the variation in the
consumption demand
- the compressor size and the
modulation strategy
In general it is possible to calculate
the maximum consumption in the system by summarizing the demand of
each consumer. The summarized consumption must be multiplied with
a
- usage factor ranging
0.1 - 1
depending on the system. In practice
it is common that the manufacturer use standardized receivers for
specific compressor models based on their know-how.
For calculating the receiver, note
that it is necessary with a pressure band for the
receiver to be effective. If the consumption process requires
100 psig and the compressor is set to 100 psig,
there is no storage and no buffer. Any increased demand makes a
pressure drop below 100 psig until the compressor controls
respond by increasing the volume compressed.
If the compressors operates at 110
psig the difference between 110 psig and 100
psig accounts for the air stored in the receiver. If the
demand increase, the pressure can drop 10 psig before the
minimum requirement is met. Pressure and flow controllers can be
used after the receiver for stabilizing downstream pressure to
100 psig and flattening demand peaks. Note that in a
compressed air system the pipe work also makes the purpose of a
buffered volume.
The receiver volume may be
calculated with the formula:
t = V (p1 -
p2) / C
pa
(1)
where
V = volume of the receiver tank
(cu ft)
t = time for the receiver to go
from upper to lower pressure limits (min)
C = free air needed
(scfm)
pa= atmosphere pressure
(14.7 psia)
p1 = maximum tank
pressure (psia)
p2 = minimum tank
pressure (psia)
It is also common to size
receivers:
- to 1 gallon for each ACFM
(Actual Cubic Feet per Minute), or
- 4 gallons per compressor hp
(horse power)
