Use the working liquid volume
A vessel has geometric volume, usable liquid volume and reserved headspace. These are not interchangeable. The working range between agreed fill and discharge endpoints gives the product volume moved in one cycle. Headspace, residual liquid, foaming and instrumentation may reduce the usable fraction. The proposal should state the working volume used in the capacity calculation rather than relying only on the vessel nameplate size.
Calculate a first-pass average
For identical vessels completing independent cycles, a screening expression is Q = N × Vuse × 3600 / tcycle, with Q in m³/h, N the number of vessels, Vuse in m³ and complete cycle time in seconds. For an illustrative two-vessel system moving 1.2 m³ per vessel every 300 seconds, the arithmetic gives 28.8 m³/h. This is a calculation example, not a SINOSEN rating. Shared feed, discharge and air limitations can reduce that result.
Check the schedule, not just the equation
Break the cycle into filling, isolation, pressure build-up, discharge, depressurization and any waiting period. Overlay the two vessel schedules. If filling takes longer than the companion vessel can sustain discharge, a gap remains. If both demand high air flow at the same moment, header pressure can drop. A realistic model includes downstream permissives and valve transition times.
Prove the result during acceptance
Specify the test product or a justified equivalent, temperature, route, tank levels and available utility pressure. Measure net delivered liquid over enough complete cycles to include the changeovers. Report both average throughput and the outlet-flow behavior required by the process. A short maximum-rate observation should not be presented as sustained production capacity.
General engineering guidance. Numerical examples are illustrative; project specifications and acceptance criteria are agreed for the actual duty.