9
DESCRIPTIONS OF FUNCTIONS
LEISTER TWINMAT
•
Heating system
The hot air temperature is electronically steplessly adjusta-
ble and electronically controlled for heating up the hot air wedge. Digital
display of SET and ACTUAL value. The flexible hot air wedge has three heat
zones:
Pre-heating, contact heating, material plasticising with hot air.
•
Welding pressure
steplessly adjustable, digital ACTUAL value display. The
welding pressure is transmitted via the toggle lever to the pressure rollers.
During the welding process the pressure is matched linearly to the change
in thickness of the membrane (e.g. T-joint).
•
Drive
electronically steplessly adjustable and electronically controlled. Digi-
tal display of SET and ACTUAL value. The power transmission works through a
three stage planetary gear. Should rippling occur in the laid-out geomem-
brane liners, the upper or lower drive/pressure roller can be switched over
alternatively.
D
C
D
B
A
Cross-sectional diagram of an overlap weld
Seam thickness reduction = A – B
A :
Thickness of upper and lower
geomembrane liner
B :
Thickness of welding seam
C :
Width of test channel 15 +/- 2 mm
D :
Width of weld
≥
15 mm
•
Welding seam geometry
The proof of quality in a welding seam (peel test,
tensile test) depends upon the thickness reduction in the area of the seam.
With a seam thickness reduction ranging between 0.4 – 0.8 mm, the welding
seam geometry is within the permissable range (DVS 2225 part II, BAM). This
permissable range reflects the optimum interaction of welding parameter
temperature, welding pressure and speed under changing ambient condi-
tions during the welding process.
