Precision work on the ground floor
Wolfsburg, December 2015 – Dürr had to meet demanding energy-efficiency specifications from the customer when upgrading ovens and exhaust-air purification systems in the VW plant in Wolfsburg, Germany. The tight space available represented a further challenge. Working very closely together, the colleagues from Dürr’s Paint and Final Assembly Systems and Clean Technology Systems divisions mastered this project and installed two customized Ecopure TAR systems.
The oven upgrades took place in five stages from the end of 2012 until January 2015. It was the turn of the primer oven and exhaust-air purification systems in the final stage. VW’s aim was not only to improve quality and the maintenance, repair and cleaning options, but also to save energy.
In the thermal exhaust-air purification process with a Dürr Ecopure TAR system a burner heats the solvents and plasticizers released during curing of the bodywork to approx. 710°C and renders them harmless as a result. The clean gas produced during this combustion process exits the TAR via the integral heat exchanger at a temperature of about 440°C. The residual heat is used to heat the oven zones.
As a result of the high PVC content in the frequently used joint seals, the plasticizer and solvent vapors contained in them are released in the primer oven and result in relatively marked formation of condensation at the cooling zone infeed. The Dürr team therefore optimized the primer oven by specifically extracting these fumes. The increased exhaust-air volume required more powerful fans and new thermal exhaust-air purification systems.
Reducing heat losses
“VW wanted high-efficiency systems which ensure lower natural gas consumption for heating the ovens,” declares Werner Zondler, the Sales Manager for exhaust-air purification systems at Dürr. His colleagues therefore came up with a customized solution using a specially designed heat exchanger to preheat the air to a high temperature. Furthermore, thicker insulation in the Ecopure TAR systems minimizes the losses as a result of heat emission.
During the upgrade project the location of the exhaust-air purification systems was changed: The new Ecopure TARs are now on the ground floor instead of one floor higher. Dürr service staff performed extensive preliminary work such as creating new ceiling openings to modify the ducting and removed other obstructions. For example, they laid paint feeder hoses, raised water pipes and adapted a CO2 line and a natural gas line. Because of the low ceilings on the ground floor, the exhaust-air purification systems are longer than usual and have removable feet. Otherwise, it would not have been possible to get them through the building openings. For that reason, the Ecopure TARs were only fitted with insulation mats and metal jackets once they were positioned in their intended final location. There is only minimal clearance from the building pillars on the ground floor. “Erecting and adjusting the equipment called for precision work,” summarizes Sales Manager Werner Zondler.
Project Manager Roland Hess came up with a particular idea which saved several days. He manufactured a dummy fan, then positioned it such that it was possible to install piping sooner and prepare connections.
Meticulous planning was needed in order to meet the tight three-week schedule during the plant’s annual closure. The Dürr team held many meetings to discuss how VW’s requirements could be implemented. “In consultation with the customer, we have designed and installed showcase lines for the entire VW Group,” states Project Manager Roland Hess.