Airless Paint Sprayer

Overview

An airless paint sprayer atomises paint by pressure alone. A piston pump raises the coating to around 200 bar and forces it through a tungsten-carbide orifice a few tenths of a millimetre across; the emerging sheet of liquid tears itself apart into droplets as it decelerates against the air. Because no compressed air is mixed into the stream, transfer efficiency is higher than conventional air spraying, the fog is heavier-bodied, and the machine handles thick architectural coatings, emulsions, primers, elastomerics, without thinning. Airless is the standard method for repainting building exteriors, interiors of any size, fences, roofs and steel, laying down paint five to ten times faster than rolling.

How it works

Paint is drawn straight from the bucket through the Suction Set: the Suction Tube reaches the bucket floor and the Inlet Strainer screens out skins and grit. The heart of the machine is the Piston Pump, a double-acting single-piston design. On the upstroke the Inlet Ball Valve ball lifts and paint fills the cylinder below the piston; at the same time paint trapped above the piston is pushed out to the manifold. On the downstroke the inlet ball seats, the Outlet Ball Valve ball inside the piston lifts, and paint transfers through the piston to the upper chamber, so the pump delivers on both strokes and pulsation stays manageable. The Piston Rod is hard-chromed and runs through stacked Packing Stacks of leather and UHMW polyethylene, the wear item that defines pump rebuild intervals.

The piston is stroked by the Motor & Drive: a Drive Motor through a Helical Gear Pair reduction to the Crank & Connecting Rod. Pressure regulation is electronic on modern machines. A Pressure Sensor on the manifold reports fluid pressure to the Control Board, which varies motor speed to hold the setpoint dialled on the Pressure Knob, the pump simply stops when the trigger closes and pressure reaches target, and restarts the instant spraying resumes.

From pump to fan pattern

High-pressure paint travels through the High-Pressure Hose, a nylon-cored line with aramid braid and a conductive layer that grounds static charge generated by paint friction. At the gun, the trigger lifts the Needle Valve off its carbide seat and paint reaches the Reversible Spray Tip. The tip is where the spray is actually made: a carbide insert with an elliptical orifice whose minor axis sets flow and whose major axis sets fan width. Tip sizes use a three-digit code, a 517 tip fans about 10 inches (first digit × 2) with a 0.017 in orifice (last two digits). Larger orifices for heavy coatings, smaller for fine finish. Tips wear open with sprayed volume; a 0.017 tip that has worn to 0.021 wastes paint and ruins the pattern, so tips are consumables replaced every few hundred litres.

Clogs are cleared without disassembly: the reversible tip rotates 180° in its Tip Guard so trigger pressure blows the blockage back out. Three filters stand between bucket and orifice, inlet strainer, Manifold Filter and the Gun Filter in the handle, each finer than the last.

Priming and pressure relief

The Prime Valve selects between two flow paths. In PRIME, pump output bypasses the hose and returns to the bucket through the Drain Tube, letting the pump flood itself and purge air at low pressure. Flipped to SPRAY, output is directed into the hose. The same valve is the pressure-relief device: the shutdown ritual is trigger lock on, prime valve open, and the trapped 200 bar in the hose dumps harmlessly to the bucket.

Safety

The hazard specific to airless equipment is fluid injection. The jet a few millimetres from a worn tip can pierce skin and inject paint into the hand; the wound looks trivial and the injury is a surgical emergency. The Tip Guard's wings keep fingers off the orifice, the Trigger Lock is engaged whenever the gun leaves the hand, and the rule taught with every machine is to never wipe the tip with a finger while pressurised.

Maintenance

Daily care is flushing, water for latex, mineral spirits for oils, until the return runs clear, since paint cured inside the pump destroys packings and valves. Pump rebuilds (packings, sleeve, balls and seats) come at roughly 2,000–4,000 L of sprayed coating. Storage involves filling the fluid section with a glycol-based pump protector to keep the Packing Stacks from drying out.