Compressor quotes stall when the inquiry is a paragraph of adjectives. Three numbers move a project from idea to proposal in one email.
1. Demand — the honest flow
Add up the tools that actually run at once, in m³/min or cfm, and resist the urge to double it. Oversizing a screw compressor buys you short-cycling, condensate and a bigger bill — not headroom.
2. Pressure — the lowest that works
Every extra bar costs roughly 7% in energy. Find the highest pressure any tool truly needs, add the network’s pressure drop, and stop there. Painting at 6 bar does not need a 13 bar compressor.
3. Hours — how long, how steady
Two shifts of steady demand point to a fixed-speed unit at its sweet spot. Swinging demand across one shift points to variable speed. The duty pattern decides the technology — say how the plant actually runs.
Then let the data argue
For existing plants we log a week of real demand before quoting. The logger has ended more sizing debates than any brochure ever will.
