Johnson Controls YORK YVAM 0350, Руководство по эксплуатации и техническому обслуживанию

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Cleaning evaporator tubes
It is difficult to determine by any particular test if the possible lack of performance of the
evaporator is due to fouled tubes alone or due to a combination of issues. Problems that develop
because of fouled tubes are indicated when, over time, the cooling capacity decreases and the
split increases. The split is the temperature difference between water leaving the evaporator and
the refrigerant temperature in the evaporator. A gradual drop-off in cooling capacity can also be
caused by a gradual leak of refrigerant from the system or by a combination of fouled tubes and
shortage of refrigerant charge.
Tube fouling
Fouling of the tubes can occur due to the following types of deposits:
• Rust or sludge: This can enter the tubes and accumulate there. This material usually does not
build up on the inner tube surfaces as scale, but does interfere with the heat transfer. Rust or
sludge can generally be removed from the tubes by a thorough brushing process.
• Scale: This develops due to mineral deposits. These deposits, even though very thin and
scarcely detectable on physical inspection, are highly resistant to heat transfer. They can
be removed most effectively by circulating an acid solution through the tubes using skilled
experts as described in the following section.
Tube cleaning procedures
The main methods of cleaning tubes includes brush cleaning and acid cleaning.
Brush cleaning of tubes
If the tube consists of dirt and sludge, it can usually be removed using a brushing process. Drain
the water sides of the evaporator circuit, remove the heads, and thoroughly clean each tube with a
soft bristle nylon brush.
Note: Do not use a steel bristle brush. A steel brush can damage the tubes.
For improved results, flow water into the tube during the cleaning process. To set this up, mount
the brush on a suitable length of 1/8 in. pipe with a few small holes at the brush end and connect
the other end of the pipe with a hose to the water supply.
Always clean the tubes with a brush before using acid cleaning.
Acid cleaning of tubes
If the tubes are fouled with a hard scale deposit, they might require acid cleaning. Before acid
cleaning, it is important to clean the tubes using the brushing process described previously. If
the relatively loose foreign material is removed before the acid cleaning, the acid solution has
less material to dissolve and flush from the tubes. This process saves time and results in a more
satisfactory cleaning job.
WARNING
Acid cleaning must only be performed by an expert. Consult your local water treatment representative
for assistance in removing scale buildup and for preventative maintenance programs to eliminate
future problems.
Commercial acid cleaning
In many major cities, commercial organizations now provide a specialized service of acid cleaning
evaporators. If acid cleaning is required, use of this type of organization for best results. The Dow
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