Welker - VACUMASTER Glass Fiber Dryers

The vacuum drying process for glass fibre yarns processing is a new engineering solution of WELKER, based on the experience of manufacturing autoclave solutions for the textile industry. The solution has been engineered in co- operation with a global glass fibre yarn producer.

In the spinning process, the fiberglass spin cakes undergo a sizing treatment in a wet environment. The water content after this sizing process is approx. 10 – 12 % in the spin cakes. For the subsequent winding process they need to be dried. The envisaged maximal moisture content should be 0.5 to 1 %.

The drying operation normally is performed in conventional heating ovens, with the following characteristics:

• High energy consumption,
• Very long process duration with up to 36 hours process time,
• Lack of uniform drying results as the outer and inner layers of the spin cakes cannot be utilized,
• Eventual deterioration of the sizing properties due to damages caused by too high temperatures,
• Considerable waste of fiberglass material.

With such standard dryers, the risk is that the binder applied to the yarn will deteriorate when the applied temperatures are too high, damaging the yarn. Furthermore, the process needs substantial utilisation of energy and high manufacturing costs.

The WELKER VACUMASTER has been installed in an European production plant to the entire customer satisfaction, demonstrating good results and having achieved all targets expected at the start of the development.

Vacuum drying as problem solution

In order to establish an innovative and highly efficient drying process, extensive trials with a prototype were made.

The results of these trials have lead to the conclusion that ULTRAVacuum conditions in alternation with accurately controlled heating phases offer a unique combination for the process. The vacuum technology reduces the existing process time by approx. 40- 50 % with significant better quality results.

Furthermore, the combination of vacuum and controlled heat reduces the energy costs of the drying process by up to 50 % or even more.

The textile properties of the yarn have increased significantly as there are no damages to the sizing material and the tensile force has consequently increased. Additionally, the new technology ensures absolute uniformity of the drying process , thus eliminating waste of fibre material.

Production process description

The glass yarn is produced and wound up on a carton tube (spin cake). The packages are put on a pin truck which accommodates up to 46 glass packages. The loaded trucks are weighed and transported to the VACUMASTER vacuum dryer. The VACUMASTER in case has been designed for a maximum capacity of 6 trucks. The loading and the door systems are controlled automatically.

Depending on the various types of binder material applied to the glass yarn, a specific vacuum drying programme is chosen by the operator and the process cycle is started. After preheating the glass to a specific temperature, vacuum is being applied, taking the humidity out of the vessel.

After finishing the process, the VACUMASTER stops automatically, opens the door and unloads the vessel, transporting the pin trucks out of the machine.

• Slow approach of vacuum peaks in order to avoid deformation of the spin cakes
• Maximal vacuum peaks of up to 98%, followed by heating peaks of up to 110°C
• Alternating sequences of up to 120 movements or more
• The residual humidity is gradually evaporated down to 1-3 %within approx. 12- 18 hours

WELKER Thermozone- System

The cylindrical design of the autoclave offers different air flow properties at the middle and edges. This demands individual adjustment of the heating temperature in various areas.

Therefore, with the WELKER THERMOZONE- System, the heating phase of each cycle can be adjusted individually in various thermal areas inside the machine body.

Process adjustment

The process is based on fine adjusted sequences of vacuum and temperature peaks. The approaches to these peaks are slow and gradually incremental, controlled by the WELKER DOSITRON 18 PLC controlled automation system.

Automation alternatives

The picture indicates the various possibilities of loading/ unloading VACUMASTER machines. Apart from these, other configurations are possible. Please ask for more information.

Technical data of VACUMASTER

• Product: Glass fibre yarn
• Moisture content wet package 10- 11%
• Moisture content dried package max. 2%
• Package weight in average 13.0 Kg
• Package weight max. 17.5 Kg
• Truck load in average 598.0 Kg
• Dryer average temperature 88°C (min. 85°C, max. 93°C)
• Dryer pressure - 95.0 kPa ( min. –88.0 kPa, max. – 100.0 kPa)
• Packages per pin truck 46
• Number of trucks per load 6
• Batch load in average 3,588 Kg
• Maximum vacuum % 97.0%
• Maximum temperature 120°C