Welker - Vacuum Steaming and Heat Setting

Each production step (spinning, twisting, knitting….) causes tension in yarn and fibre. Yarns tend to snarl in order to relax themselves. Tension and snarling may lead to problems in downstream processing. Man made fibres are shrinking to relax stress in the molecular structure. VAPOMAT vacuum steamers provide optimal performance.

Relaxation by vacuum steaming is essential in following applications:

• Heat-setting of wool yarns
• Fixation of texturized PES
• Fixation of twisted PES Filament
• Fixation of sewing thread
• Heat setting of core yarns (Lycra)
• Fixation of knitted mesh (crimped fibre)
• Relaxation of high twisted yarns
• Steaming of T/C yarns
• Relaxation of ring yarns
• Stabilisation of manmade fibre
• Tow Annealing (Acrylic Tow)

Each material requires a specific process to get the desired effect. Temperatures range from 45°C to max. 150°C. Saturated steam is the ideal medium for the relaxation process. It easily penetrates into the yarn packages due to high vacuum and releases itīs energy during condensation. The yarn is heated up to the desired temperature which is carefully kept within narrow tolerances.

Steaming Programs (cycles)

The basic rule is:
As little as possible - but as much as necessary to keep thermal treatment at minimum level. Depending on the desired degree of liveliness the parameters temperature, time, vacuum and no. of cyles can be varied for optimal results. For man made fibre the remaining shrink for subsequent dying determines the variables.

A typical steaming cycle with all characteristic steps:

• Preheating
• Initial vacuum
• Steam
• Final vacuum
• Pressure Balance

Depending on the material the parameters are varied for optimal and smooth treatment

The unique Welker preheating system

Wet spots on the yarn are a well known problem in yarn steaming. Water spots may result in dye variations or other problems in downstream processing. Preheating is absolutely essential in steaming of wool yarns.

Saturated Steam

VAPOMAT yarn steamers are either fed from attached electric steam boiler (Welker SATURATOR) or with steam from oil- or gasfired boiler (boiler house). HP steam is converted to low temperature saturated steam with a desuperheater (steam cooler) after pressure reduction.

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