on . Posted in Instrumentation & Controls

This calculation uses the air consumption rate of the instruments and determines the size of an air receiver based on the time required to meet a minimum pressure. The minimum pressure is generally the low pressure set point of a compressor. The initial pressure is the design pressure the receiver. The calculation is displayed symbolically as:

If the compressor only runs when the low level pressure is met, then the Flowin would equal zero.

$$\large{ AR = \frac{ p_{atm} \: t \; \left(Q_{out} \;-\; Q_{in} \right) }{p_i \;-\; p_f } }$$
Symbol English Metric
$$\large{ AR }$$ = air receiver size $$\large{gal}$$  $$\large{L}$$
$$\large{ Q_{in} }$$ = flow in $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$
$$\large{ Q_{out} }$$ = flow out $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$
$$\large{ p_{atm} }$$ = atmospheric pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ p_f }$$ = final pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ p_i }$$ = initial pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ t }$$ = time $$\large{sec}$$ $$\large{s}$$