Extraction Systems for Metalworking and Machinery

Metalworking shops release three main contaminants into the air: welding fume, oil mist from machining, and grinding and sanding dust. Each has a different particle size and behaves differently; if you try to collect them with the same system, none of them is captured efficiently.

Welding fume

Welding fume consists of very fine particles that stay airborne for a long time and reach deep into the lungs when inhaled. The visible blue smoke is only part of the particle load.

The solution is source capture. Articulated extraction arms are used at manual stations and cell-based extraction in robotic cells. The system is sized for the number of stations running at the same time; each arm has an automatic damper so unused arms are closed.

Because hot particles can enter the duct during welding and cutting, a spark arrestor or drop-out box is provided before the filter.

Oil mist

On CNC machines, coolant is atomised in the cutting zone and spreads into the room. The result is twofold: operator exposure, and an oil film building up on floors, surfaces and electrical panels. The oil film increases the risk of slips and shortens the life of electronic equipment.

The solution is oil mist separators that extract from the closed volume inside the machine. Separation is usually staged: a mechanical pre-separator catches large droplets and the main filter handles fine mist. The captured oil can be drained back to the machine.

Grinding and sanding dust

Unlike welding fume, these particles are heavy and abrasive. Conveying velocity must be maintained in the ductwork; if velocity drops, dust settles and the line clogs. Bends and impact points are made from heavy gauge sheet to resist wear.

In most facilities metal dust is a recoverable material; the collection hopper under the filter unit is chosen accordingly.

General workshop ventilation

Once these contaminants are captured at source, what remains is general workshop ventilation: removing the heat produced by the machines and balancing fresh air. If controlled fresh air is not supplied to a workshop with extraction, the space falls into negative pressure, doors become heavy and cold draughts form in winter.

Workplace air monitoring

Welding fume and oil mist are contaminants tracked in workplace exposure monitoring. Having workplace air measured after the extraction system is installed both documents that the obligation is met and shows that the system really works. If the measurement is higher than expected, the problem is usually in one of three places: the hood is too far from the source, the airflow is insufficient or the filter is clogged.

Phased investment

In metalworking shops it is often not necessary to solve every area at once. During the survey we identify which contaminant causes the most problems in which area, and the investment starts there.

A common order is: first the welding area, because exposure is highest and the complaint most concrete there. Then oil mist in the machining area, then grinding dust, and finally general workshop ventilation.

Designing the line so branches can be added later makes this phased approach possible. If the fan and filter unit are selected one size up in the first phase, the system does not have to be rebuilt when later areas are connected.

A common mistake

The most common mistake in metal shops is buying one big fan and connecting every point to it. Welding fume, oil mist and grinding dust need different filter technologies; collected in a shared line, the oil turns the dust into sludge and the filter quickly becomes unusable. The right approach is separate lines for contaminants of different character.