Ventilation for Plastics and Rubber Production

In plastics and rubber production, the decisive ventilation load is heat. Injection moulding machines, extruders and presses all run at high temperatures to melt material, and a large part of this heat spreads into the room. In summer, working temperatures in these areas quickly reach unacceptable levels.

Removing process heat

A system installed without calculating the heat load cannot bring the temperature down, despite a high air change rate. The problem is not that the air is not renewed, but that heat is being added to the room continuously.

The effective approach is to capture heat at source: local hoods over the hot zones of the machines exhaust hot air directly before it spreads into the room. The remaining load is handled by general ventilation. This twofold approach achieves the same result with a much lower total airflow.

Fumes, odour and released gases

Fumes and odour from melting plastic vary with the material and process temperature. PVC, rubber and some compounded materials produce a noticeable odour.

Here too, extraction is done at source: local extraction is placed over extruder outlets, mould openings and hot cutting points. If odour reaching neighbouring areas and the surroundings is a problem, activated carbon after the particle filter is considered. Activated carbon only makes sense for gases and odours; placed before the particle filter it fills quickly and stops working.

Granule conveying and dust

Pneumatic conveying of raw material granules generates fine dust and static electricity. Local dust collection is applied at silos and feed points. Some plastic dusts can form explosive clouds under the right conditions; in that case the filter unit, earthing and explosion venting are assessed separately.

Rubber production

Rubber mixing and vulcanisation areas have both high temperatures and a strong odour. The compound preparation area handles very fine powders such as carbon black; these are light, easily become airborne and stick to surfaces. In these areas extraction is handled separately for dust and for odour.

Points to watch

In this sector it is important to plan the ventilation system around the equipment layout. When the machine layout changes, the extraction points change too; designing the line so branches can be added later avoids renewing the whole system a few years down the line.

Heat recovery is particularly worthwhile in this sector: the exhaust air is warm all year and can be used to heat the fresh air in winter.

Energy recovery

In plastics and rubber production, the exhaust air is warm all year round. This is an opportunity most sectors do not have: heat in the exhaust air can be recovered and used to heat the fresh air in winter.

The type of recovery unit is chosen according to what the exhaust air carries. On lines carrying fumes and odour, plate or run-around coil types, where the two airstreams do not mix, are preferred; rotary types are not suitable in this case.

The payback period is directly linked to operating hours. In a facility running three shifts, payback is significantly shorter than in one running a single shift.

Start with measurement

In this sector the complaint usually comes as "you can't work here in summer". But ventilation is not always the source of the problem; sometimes a shortfall in the machines' cooling water circuit releases extra heat into the room. During the survey, room temperature, machine surface temperatures and the actual airflow of the existing ventilation are measured together.