For a sorting plant running three shifts, several compressors beat a single one in most cases: air stays available during servicing or a breakdown, and output follows a material stream that keeps changing. A single large compressor makes sense when space or installation cost comes first, provided you plan a backup. The right choice comes down to three figures: average flow, peak flow, and the minimum flow below which sorting stops.
The air needs of a whole site (sorters, balers, dust collectors) are covered on our page on the compressor for recycling and waste sorting. Here we look at how to lay out the compressed air plant.
What three shifts mean for the compressor
A compressor running 24 hours a day, 5 days a week, clocks up 120 hours a week. Our screw compressors need a first service at 500 hours, then one every 1,500 hours:
- First service: 500 / 120 = about 4 weeks after start-up
- Following services: 1,500 / 120 = about every 12 to 13 weeks
- On 7 days a week (168 hours a week): about every 9 weeks
Every service means stopping the compressor. With a single machine, that stops the sorting, or means arranging a stand-in machine each time. With several machines, the others keep running while one is serviced.
A worked example
A sorting plant uses 6.0 m³/min on average at 8 bar, with peaks of 7.0 m³/min. Below 5 m³/min, the sorters lose accuracy and the line has to slow down.
Option A, one high-power compressor. Beyond 22 kW, the S series goes up to 132 kW on request. One machine, one electrical connection, one dryer. But during servicing or a breakdown, the flow drops to zero.
Option B, three S 220 PM units. Each delivers 3.6 m³/min at 8 bar:
- All three together: 3.6 + 3.6 + 3.6 = 10.8 m³/min, well above the peak
- One machine stopped: 3.6 + 3.6 = 7.2 m³/min, the 7.0 m³/min peak is still covered
- Two machines stopped: 3.6 m³/min, below the 5 m³/min threshold, the line slows
This is the "one machine more than you need" approach: full flow is kept with one machine down for servicing.
Option C, two S 220 PM and one S 110. The S 110 delivers 1.7 m³/min at 8 bar. Together: 3.6 + 3.6 + 1.7 = 8.9 m³/min. If one S 220 PM stops, 3.6 + 1.7 = 5.3 m³/min remains: above the 5 m³/min threshold, but below the average. Cheaper than option B, with a tighter fallback mode.
Sharing the load between machines
S series compressors run at variable speed: each one matches its output to demand. With several machines in parallel, you need to stop them working against each other. Our technicians set staggered pressure set points so that one machine carries the base load and the others follow the swings. Also rotate the base-load role to spread the hours and stagger the services. See variable speed or fixed speed.
Points to check before choosing
- Air treatment. A single dryer for three compressors becomes a single point of failure again. One dryer per compressor, or a dryer with a bypass, keeps the backup advantage.
- Space in the plant room. An S 220 PM measures 1100 × 850 × 1000 mm and weighs 310 kg. Three machines need floor space and ventilation that removes the heat of all three. See the compressor room.
- Electrical supply. Each machine connects to a 380 V three-phase supply. Check the power available at the switchboard for the whole set.
- Energy. Compare the options with the compressor electricity cost calculator. A compressed air audit shows the real consumption of an existing site, hour by hour.
Backup and servicing
Even with several machines, prepare for the unexpected. A rental screw compressor from 5.5 to 132 kW can stand in during a repair. Our service kits group the air filter, oil filter and air/oil separator for each model: on three shifts, keep some in stock. Our maintenance plans hand the follow-up to our technicians and partner dealers. AIRSTAHL compressors carry a 2-year warranty, with spare parts available for 15 years.
Describe your site (sorters, balers, shifts, current flow) in a quote request: we will compare the possible layouts with you. For an installation of this size, see also our industrial projects.
For your trade: Compressor for recycling and waste sorting.