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8.3 - Plate heat exchanger cleaning
In some applications, for example when very hard water is
used, there is more tendency for fouling. The heat exchanger
can always be cleaned by circulating a cleaning fluid.
A weak acid solution should be used (5% phosphoric acid or, if
frequently cleaned 5% oxalic acid), and the cleaning fluid should
be pumped through the heat exchanger (Fig. "Tank installation").
The tank installation can be permanent or, alternatively, the
connections can be prepared and, at any given time, a portable
cleaning device can be connected.
To achieve optimum cleaning the acid solution should be
circulated at a minimum of 1.5 times the normal operational
flow speed, and preferably in reverse direction. The installation
should then be flushed with large amounts of water to totally
remove the acid before the system is started up.
Tank installation
1
Legend
1
Heat exchanger
2
Weak acid solution tank
Cleaning should be done at regular intervals and should never
be left until the unit has become blocked. The time intervals
between cleaning depend on the quality of the water used, but
as a general rule it is advisable to clean it at least once a year.
8.4 - Refrigerant circuit
Ensure that there is no leakage of refrigerant or oil from the
compressor. Check that the high and low side operating pressures
are normal. Check the cleanliness of the refrigerant-water heat
exchangers by checking the pressure drop across them.
8.5 - Controls
Check the operation of all relays, high/low pressurestats and
controls.
22
9 - SERVICE
9.1 - Lubrication
The compressor has its own oil supply and oil should not be
added unless a leak has occurred.
9.2 - Servicing recommendations
-
Before replacing any of the elements in the cooling
circuit, ensure that the entire refrigerant charge is removed
from both the high and low pressure sides of the unit.
-
The control elements of the cooling system are highly
sensitive. If they need to be replaced, care should be taken
not to overheat them with blowlamps whilst soldering. A
damp cloth should be wrapped around the component to
be soldered, and the flame directed away from the
component body.
-
Always use silver soldering rods.
-
If the total unit gas charge has to be replaced, the quantity
should be as given on the nameplate and the unit should
be properly evacuated beforehand.
-
During unit operation all panels should be in place,
including the electrical box access panel.
-
If it is necessary to cut the lines of the refrigerant circuit,
2
tube cutters should always be used and never tools which
produce burrs. All refrigerant circuit tubing should be of
copper, specially made for refrigeration purposes.
-
If a temperature sensor needs to be replaced, the new
sensor should be correctly installed. The sensor cable must
be positioned as the original sensor cable.
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