28
7
4
6
2
8
3
5
1
9.4.3 - Replacing cooler tubes
Retubing must be done only by a properly trained service
engineer. Most standard practices can be applied, but for
cooler tubes a 5% crush allowance is made for tube expan-
sion and twisting (15.87 mm diameter tubes are used in
these coolers).
The table below gives the specification of the materials used.
example:
Tube sheet hole diameter
16.00 mm
Tube outside diameter
15.87 mm
Clearance
0.13 mm
Tube inside diameter before rolling
14.27 mm
Tube inside diameter after rolling
14.48 mm
NOTE: Tubes next to the gasket webs must be flush with
the tube sheets at either end of the cooler.
9.4.4 - Preparation of gaskets
When rebuilding the cooler, new gaskets must always be
used. They must conform to the Carrier specification for
compressed gaskets.
•
Clean the gasket and its place on the tube sheet.
•
Cover the two matching surfaces (gasket and tube
sheet) with adhesive, and stick them together.
•
Let the joint dry for 5 minutes.
•
Moisten the joint with a small amount of compressor
oil.
•
Reinstall the evaporator head within 30 minutes.
9.4.5 - tightening cooler head bolts
Cooler head bolts must be tightened in the specified
sequence and to the correct torque.
9.4.6 - tightening sequence
The following tightening sequence is recommended:
•
Hand tighten the first four bolts as shown below in
stage 1.
•
Hand tighten the next bolts as shown below in stage 2.
•
Starting at the 12 o’clock position, and working clock-
wise, insert and hand tighten the remaining outer bolts.
•
Insert and tighten the six screws in the center of the
head.
•
Starting again at 12 o’clock and working clockwise
tighten the outer bolts to the correct torque.
•
Not less than one hour later insert and tighten the six
bolts in the centre of the head, using the torque values
given.
•
After the cooler has been refilled with clean refrige-
rant, use a soap and water solution or an electronic
detector to confirm that there are no leaks.
•
Replace the evaporator insulation and temperature
sensors.
Stage 1
Bolt size M12 - 71-87 Nm
Bolt size M16 - 171-210 Nm
Bolt size M20 - 171-210 Nm
Stage 2
9.5 - Corrosion control
All metallic parts of the unit (chassis, casing panels, control
boxes, heat exchangers, etc.) are protected against corrosion
by a coating of powder or liquid paint. To prevent the risk
of blistering corrosion that can appear when moisture
penetrates under the protective coatings, it is necessary to
carry out periodic checks of the coating (paint) condition.
