Breathing Air Compressor Product

Overview

A breathing air compressor fills the cylinders that firefighters and divers breathe from, which makes it two machines in one: a high-pressure gas compressor reaching 330 bar, and a purification plant that turns whatever the intake snorkel swallows into air clean enough to meet EN 12021 or CGA Grade D/E — under 5 ppm carbon monoxide, under 0.5 mg/m³ oil, and dry enough that nothing freezes in a regulator at depth or in winter. Fire stations, dive shops, and mobile air units run units in the 250–570 L/min class, refilling a 6.8 L SCBA cylinder to 300 bar in roughly five minutes.

Compression

Reaching 330 bar in one stroke is thermodynamically hopeless — adiabatic heating would exceed material and lubricant limits — so the Compressor Block compresses in four stages of modest ratio, roughly 8:1 then 4:1, 3:1, and 3:1, with the air cooled back toward ambient between stages in finned Intercooler Coil coils. Bores shrink as pressure rises: each Stage Cylinder handles the same mass flow at higher density, from about 88 mm at stage one down to 14 mm at stage four. The final-stage Piston Set commonly uses a ringless floating piston running on a metered oil film, since ring friction at 330 bar would dominate losses. Spring-plate Stage Valve Set valves on each stage open on pressure difference alone, needing no timing gear.

A counterweighted Crankshaft in the splash-lubricated Crankcase drives all pistons; the Drive System turns it at 1200–1500 rpm through Drive Belt V-belts from a 5.5–11 kW motor, and the Flywheel Fan doubles as the cooling blower, pushing air across cylinders and coolers through the enclosure Cooling Louvre panels. Intake placement matters as much as filtration: the Intake Filter feeds from a snorkel that must be sited away from engine exhaust and floor level, because the downstream catalyst bed can only handle trace CO.

Getting to breathing grade

Compression concentrates contaminants. Each cooling step condenses water and oil mist, which cyclonic Moisture Separator units spin out of the stream; the Automatic Drain Valve solenoid blows the separators down for a couple of seconds every 15 minutes of running — the audible "burp" of a filling station — into the Condensate Tank via the Drain Manifold. Skipping drainage floods the purification cartridge with liquid water and ends its life in minutes.

Final polishing happens in the Purification System train, a replaceable cartridge inside the forged Cartridge Housing. Air passes in sequence through the Molecular Sieve Bed (13X molecular sieve adsorbing water to a dew point below −50 °C), the Activated Carbon Bed (oil vapor and odor), and the Hopcalite Bed, a manganese-copper oxide catalyst that oxidizes CO to CO₂. The ordering is functional, not arbitrary: hopcalite is poisoned by moisture, so it only works downstream of the sieve. Cartridge capacity is finite and falls steeply with intake humidity and temperature; a Cartridge Saturation Sensor moisture probe in the cartridge warns before breakthrough, and the Hour Counter backs this with a scheduled change interval. Quarterly laboratory air tests verify the output against the standard.

Filling cylinders

The operator works at the Fill Panel. The Fill Pressure Regulator selects the 200 or 300 bar cylinder class, microbore Fill Hose whips connect via DIN or CGA fittings, and the slow-opening Fill Valve meters flow because fast fills heat the cylinder — a hot-filled cylinder reads full, then cools to a short fill. After filling, the Bleed Valve vents the hose before disconnection. Stations filling fire-service cylinders put the cylinder in a fragmentation-rated fill enclosure during the fill. Overpressure protection is layered: relief valves on each stage of the block, the final Final Safety Valve, and the electronic Final Pressure Switch that stops the motor at setpoint via the Motor Contactor.

Control and protection

The Control System electronics are simple but safety-relevant: the Microcontroller monitors final pressure through a Pressure Sensor, stops the unit on the Oil Pressure Switch if lubrication fails, latches a fault on cartridge saturation, and logs run hours for maintenance. Compressor oil itself is a controlled consumable — only breathing-air-rated synthetic oils are permitted, since crankcase oil vapor is the main upstream source of both the oil and CO load the purification train must remove. The Isolation Mount under the Base Frame and the acoustic Sheet Metal Panel enclosure bring noise down to the low 60s dB(A), letting the unit live inside a station apparatus bay.