Buying an industrial compressor is not just a matter of choosing a power rating. Two quotations at the same power can lead to very different electricity bills, and a badly sized machine costs money throughout its life. A precise specification lets you receive comparable quotations and choose on total cost. This guide helps you write it.
Step 1: gather your figures
Before going to suppliers, collect your site data. The more precise it is, the more accurate the quotations.
- Air flow: average, peak and minimum, in l/min or m³/min. On an existing site, measure it over at least one week of production. See converting air flow.
- The useful pressure at the most demanding machines, and the pressure drop in the network.
- The working pattern: number of shifts (one, two or three), days per week, annual shutdowns. For a site that runs continuously, see a compressor for a three-shift plant.
- The required air quality, point of use by point of use, according to ISO 8573-1.
- The existing installation: compressors in place, age, running hours, receivers, dryers, network.
- The room: space, ventilation, electrical supply. See compressor room.
- Your electricity price, to calculate the running cost.
If you do not have these figures, a compressed air audit provides them: our technicians measure real consumption and look for leaks before sizing anything.
Step 2: write the specification
An industrial compressor specification fits on a few pages. It should contain:
- The purpose: new installation, replacement, extension or standby.
- The requirements: flows, useful pressure, air quality, working pattern.
- The site constraints: room, access, voltage (for example 380 V three-phase), maximum noise level, ambient temperature.
- The expected scope: compressors only, or a complete installation with receivers, dryers, filtration, condensate drains, oil-water separator, connection and commissioning.
- The level of continuity: is a standby machine needed (N+1 rule)? See compressed air plant.
- Control requirements: master controller, alarm reporting, consumption monitoring.
- The expected service: warranty, spare parts availability, response time, training for your maintenance team, language of the documentation.
- The documents required with the quotation: data sheets, power consumption at different loads, layout drawing, delivery lead time.
Step 3: compare quotations on total cost
Over the life of an industrial compressor, electricity weighs far more than the purchase price. Comparing quotations on price alone is therefore the main mistake. For each quotation, calculate:
- The purchase and installation price, with the same scope for all quotations.
- Power consumption on your real profile, from the power input at each load level, not only at full load.
- The flow actually delivered at your pressure, to compare the machines on the same basis.
- Maintenance planned over the period: intervals, parts to be replaced, content of the services.
Our guide compressor life-cycle cost and the electricity cost calculator help you do this calculation.
Questions to ask suppliers
- Is the machine variable speed? Over what flow range?
- What is the delivered flow at your working pressure, and to which standard is it measured?
- Are the documentation and interface in your language?
- How long do spare parts remain available?
- Who comes out in the event of a breakdown, and how quickly?
- Does the quotation include commissioning and training for your team?
- Can the heat be recovered? See heat recovery.
What AIRSTAHL offers
For an industrial project, we respond on the basis of your figures:
- Screw compressors from 5.5 to 132 kW: up to 22 kW online with their prices, from 30 to 132 kW on quotation. See our industrial compressors from 30 to 132 kW.
- Variable speed on the S and K Series, 380 V three-phase across the whole screw range.
- Full documentation, 2-year warranty, spare parts available for 15 years.
- Consumption audits by our own technicians, with a report you can view online.
Send us your specification, or simply describe your requirement from our industry page: we will propose a costed configuration.
For your trade: Compressor for industry and production, Compressor for CNC machining and machining centres, Compressor for foundries and forges.