EN
6. Commissioning, operation
14131894.02 09/2016 EN/DE/FR/ES
WIKA operating instructions model TC59-V (V-PAD
®
) 13
6.4 Tests/Checks
■
Test loop resistance of the thermocouple circuit at ambient temperature prior to welding/
routing the V-PAD
®
, record results.
■
After completing the welding/routing of the V-PAD
®
to the tube, test loop resistance at
ambient temperature and compare.
▶
If a deviation of greater than 5 % between readings occurs, please contact WIKA.
■
Perform any non-destructive examination or heat treatment as required.
■
Ensure adequate tube wall thickness at the weld locations. This can be checked by
thickness testing to customer specications.
6.5 Welding process
Gas Tungsten Arc Welding (GTAW) is the suggested welding process due to its relatively
clean weld. Small diameter ller rod (2.4 mm / 3/32" OD) and Tungsten (1.5 mm / 1/16",
2.4 mm / 3/32" OD) give the best penetration, especially for the root passes. During
welding operation, the requirements of the relevant material data sheets and the applicable
directives and standards must be considered regarding the heat treatment, ller rods
or welding procedures. Proper installation is a major step in the success of a V-PAD
®
installation. Although the V-PAD
®
is one of the most rugged sensors available, it can be
destroyed by improper welding. WIKA can supply V-PAD
®
test thermocouples on request for
practice welding if required.
6.6 V-PAD
®
welding
■
Clamp the V-PAD
®
(using a chain clamp!) to the appropriate location on the pipe. Avoid
damaging the outer surface of the V-PAD
®
when clamping.
Ensure there is good line contact with the tube (see gure 1). Avoid tilting the
V-PAD
®
and ensure the edge makes good contact with the tube (see gure 2).
Ensure good axial alignment with the tube axis (see gure 4). This will ensure
any dierential expansion of the MI cable is smooth and does not bind with the
tube clips.
■
Preheat the area to be welded (including the V-PAD
®
) as appropriate for the materials.
■
Tack weld one end of the V-PAD
®
. Visually check alignment before proceeding with the
root pass. Watch for tilt, gap, line contact, etc.
■
Attach a thermocouple meter to the cold end of the thermocouple for measurement.