13
Evaporator maintenance
Check that:
•
the insulating foam is intact and securely in place.
•
the cooler heaters are operating, secure and correctly
positioned.
•
the water-side connections are clean and show no sign of
leakage.
Multitube evaporators
The evaporator can be removed using the following procedure:
•
Close the chilled water supply and return valves (if
installed), and disconnect the chilled water supply and
return pipe connections.
•
Drain the water from the cooler.
•
Remove all temperature sensors from the cooler.
•
Fold back the insulation at the refrigerant line
connections.
When the evaporator heads and manifolds are removed, the
outer tube end plates will be visible.
Four evaporator tubes on 30GH/GZ 040-060 units and six
tubes on 30GH/GZ 085-245 units are swaged into the end plate
and cannot be removed. A dot punch mark in the end plate
opposite each one identifies each of them. If any of them
develop a leak, the tube must be plugged, as described below.
Plugging evaporator tubes
A leaking tube can be plugged pending replacement. The
number of tubes plugged will determine when they should be
replaced. Check with Carrier the effect upon chiller performance
of plugging a number of tubes. Carrier will need to know the
number of tubes to be plugged and their positions. The figure
below shows the Elliott method of plugging tubes.
WARNING: Take care when inserting plugs not to damage the
plate material between the tubes. Avoid excessive force. Clean
all components with Locquic N and then coat all surfaces with
several drops of Loctite 75 to ensure a good seal without
applying excessive force.
Elliott tube plug
Components
Part number
Tube brass plug
---T-853--103500S-*
Tube brass ring
---T-853--002570S-*
Brass plug (holes without tubes)
---T-853--1031—S-*
Brass ring (holes without tubes)
---T-853--002631S-*
Loctite
No. 75*
Locquic
“N”*
* Order directly from your Carrier distributor
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 expansion 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.
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.
Tightening cooler head bolts
Cooler head bolts must be tightened in the specified sequence
and to the correct torque.
Use this tightening sequence:
•
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 clockwise,
insert and hand tighten the remaining outer bolts.
•
Insert and tighten the six screws in the center of the head.
Plug
Ring
Tube plate
•
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 refrigerant,
use a soap and water solution or an electronic detector to
confirm that there are no leaks.
•
Replace the evaporator insulation and temperature sensors.
7
4
6
2
8
3
5
1
Bolt size M12 - 71-87 Nm
Bolt size M16 - 171-210 Nm
Bolt size M20 - 171-210 Nm
Stage 2
Stage 1
