Bertone chooses Zander air dryers

Bertone SpA of Turin, the specialist automotive design group, have specified Zander equipment to purify the compressed air in a new paint spray line for their Turin car manufacturing facility.

Bertone SpA of Turin, the specialist automotive design group, have specified Zander equipment to purify the compressed air in a new paint spray line for their Turin car manufacturing facility.

Besides their work as a leading automotive design studio, Bertone offer a production service for car manufactures, producing complete vehicles such as the Fiat Punto Cabrio as well as applying the flawless enamel paintwork for the Fiat Barchetta and Lancia K Coupe.

The company is also scheduled to produce the BMW-Scooter C1 and two new Opel models.

The new paint spraying installation at Bertone has been designed to the very highest standards and looks more like a microchip manufacturing facility or a hospital than a paint shop.

A sterile environment prevents impurities getting into the air, workers wear sterile clothing, the paint spray line moves on gleaming floors and is surrounded by glass walls.

Naturally, car bodies are painted by robots not humans and are driven by computer into the individual bays of the paint spray line.

Even colour changes are fully automatic.

In such an environment Bertone recognised that compressed air was a vital part of the painting process.

They specified Zander vacuum heat regenerated adsorption dryers and high performance filters, secure in the knowledge that their performance is validated by an independent institute to ensure that the compressed air is always free from contaminants.

The reason for the exacting specification is entirely economic.

Even the smallest particles can impair the quality of the paint and require expensive and time-consuming repairs.

The particle filtration of the compressed air is vital to ensure that no contaminant mixes with the paint process.

As well as air purity (i.e particle removal) the dryness of the air was also a vital element of quality control.

To remove water, two Zander WVN vacuum heat regenerated adsorption dryers, which have particularly low dewpoint temperatures, were installed.

Explaining the choice of vacuum heat regenerated dryers, Zander's UK managing director Nigel Morris says the two conventional methods of removing moisture from the compressed air system are refrigerant drying and heatless adsorption drying, neither of which was considered satisfactory for the Bertone installation.

In refrigerant dryers, compressed air flows through a refrigerant circuit, cooled to +3C to remove surplus water.

For many applications however, amongst them the spray painting process, a dewpoint of +3C does not remove sufficient moisture.

With heatless adsorption dryers dry air at ambient temperature flows through the regenerating vessels and expels moisture trapped in the desiccant.

Whilst these dryers reach dewpoints of down to -70C with relatively small energy use, there is a loss of between 12% and 18% of dried compressed air.

The losses can be reduced (to between 5% and 7%) by warming the air to around 150C but the saving have to be justified against the additional energy required to blow the air through heater elements and heat it! Zander's drying option - 'vacuum regeneration' - made both economic and technical sense to Bertone.

For this method, developed and patented by Zander in their range of WVN dryers, no dried compressed air is needed as recycled air.

The energy requirement is also smaller than using conventional heated regeneration because the vacuum supports the desorption of the water particles out of the desiccant.

In WVN adsorption dryers a vacuum pump sucks the ambient air through the filter, heating elements and desiccant bed, and vents it.

This ensures that both vessels have low pressure, a low dewpoint and a low heat temperature (approx 130C).

When the heating temperature is reached, the heating elements switch off and the vacuum pump is reactivated to bring the absorber bed back to operating temperature.

The vacuum pump carries out the complete regeneration process and, unlike the other two regeneration systems, no dried compressed air is needed.

The advantages of the vacuum drying option are therefore obvious.

Both compressed air installation and dryer can be matched to the exact volume of air used and it is not necessary to specify an oversized system to compensate for the regenerated air.

Less energy is also required and double the operating costs can be saved.

For all these reasons Bertone specified the two WVN adsorption dryers for their installation - a decision which has been vindicated by the high quality of air produced and the significantly lower quota of manual repairs required since the new paint bays were installed.

Other vital components in the new Bertone paint installation are Zander high performance paint compatible filters for the removal of dirt particles.

These filters are high-grade versions of the company's successful high performance pleated filter elements that are subjected to additional intensive cleaning processes during manufacture - including plasma cleaning -which removes all harmful or diffused substances They were developed in association with the Fraunhofer Technical Institute in Germany and their performance has been independently tested and validated.

They provide at least four times greater surface area than conventional wrapped elements and are totally free from silicon, which can cause serious problems with paint finishes.

As a result of the development work, Zander have created a new standard and specification (L-025) for paint compatible filters.

For Bertone, the performance difference was decisive.

When the two-layer elements they previously used were tested, they measured values of 0.0011mg/m3 at 1 bar and +20§C, whereas the high performance Zander elements measured no residual oil at all! The high performance Zander filters also registered a very small pressure drop, a high adsorption capacity and provided a longer service life.

Nigel Morris says the high performance is attributable to the pleated filter medium, which provides between 10 and 16 times more filter surface than conventional elements.

This drastically reduces the energy costs by reducing the differential pressure and the service costs by extending the service life.

He concludes by stressing that vehicle manufacturers and repairers, concerned at the cost of rectifying faulty paintwork, should consider the quality of their compressed air supply.

"Paint shops need the same compressed air quality as other motor manufacturing processes" He insists: "and that means installing desiccant dryers and efficient, silicone-free paint compatible filtration.".

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