What a Compressed Air Storage Tank Actually Does
A compressed air receiver tank stores a volume of compressed air at system pressure. When demand temporarily exceeds the compressor's output capacity — during a peak demand event — the tank supplies air from storage to bridge the gap, preventing system pressure from dropping. When demand falls below compressor output, the tank refills. The tank acts as a buffer between the compressor's steady output and the system's variable demand.
This buffering function provides several benefits: it prevents pressure drops during demand spikes, it allows the compressor to run fewer on/off cycles (reducing mechanical wear and energy consumption from inefficient cycling), and it allows facilities to meet short-duration peak demands without adding permanent compressor capacity.
Three Problems That Storage Tanks Often Solve
Problem 1: Pressure drops during peak demand. If your system pressure drops when specific equipment starts — a large actuator opens, a press cycle begins, multiple tools run simultaneously — a storage tank located near the high-demand equipment can supply air during the demand spike before pressure drops reach the point of use. This is often faster and less expensive than upgrading the compressor or distribution piping.
Problem 2: Compressor short-cycling. A fixed-speed compressor that cycles on and off more than 6–10 times per hour is short-cycling — the demand is just enough to trigger the compressor's low-pressure cut-in, but the compressor quickly satisfies demand and cuts out, only to cycle again shortly after. Each start puts stress on the motor and compressor, accelerates wear, and wastes energy. Increasing receiver tank capacity reduces cycling frequency by giving the compressor more air to pump before reaching cut-out pressure and more volume for the system to draw down before reaching cut-in pressure.
Problem 3: Insufficient capacity for new equipment. When adding new compressed air-using equipment to an existing system, the question is whether the compressor can support the additional load. In many cases, if the new equipment's demand is intermittent, additional storage capacity allows the existing compressor to meet the average demand without needing to be replaced or supplemented with another compressor.
How to Size a Compressed Air Receiver Tank
The basic formula for sizing a receiver tank to handle a demand event is:
V = (T × Q × Pa) / (P1 - P2)
Where:
- V = required tank volume (cubic feet)
- T = time of the demand event (minutes)
- Q = demand during the event that exceeds compressor output (CFM)
- Pa = atmospheric pressure (14.7 PSIA at sea level)
- P1 = initial tank pressure (PSIG + 14.7)
- P2 = minimum acceptable system pressure (PSIG + 14.7)
Example: You have a demand event that exceeds compressor output by 50 CFM for 30 seconds (0.5 minutes), starting at 100 PSIG and you cannot allow pressure to drop below 85 PSIG.
V = (0.5 × 50 × 14.7) / ((100 + 14.7) - (85 + 14.7)) = 367.5 / 15 = 24.5 cubic feet ≈ 183 gallons
This is a simplified calculation — a proper sizing analysis also accounts for compressor output during the event, tank location relative to the demand point, and piping losses between the tank and the point of use. But it illustrates how the calculation works and gives you a reasonable starting estimate.