Quantech QWC4, Installation Operation & Maintenance, Page: 143 / 156

QUANTECH
143
SECTION 7 - MAINTENANCE
FORM QWC4-NM1 (221)
ISSUE DATE: 02/28/2021
7
Non-condensable Gas
Non-condensable gas that seeped into the chiller during
incorrect evacuation or charging will also cause high
condenser approach conditions. Purge the refrigerant
vapor from the condenser into a refrigerant container
to reveal non-condensable gas.
Evaporator Tubes
Maintain evaporator water or brine flow rates through
the evaporator tubes for which the chiller was de-
signed. Refer to the engineering data on the sales order
form for the correct flow rates.
Generally, the water or brine that is circulated through
the evaporator is part of a closed loop circuit that is
treated with chemicals to prevent the formation of
scale and debris.
The evaporator's lack of performance is indicated by
cooling capacity decreases and the approach (tempera-
ture difference between the water leaving the evapo-
rator and the refrigerant temperature in the evapora-
tor) increases. It is difficult to determine if the lack of
performance is due to fouled tubes alone or due to a
combination of problems, such as:
• Refrigerant leaks from the system.
• A shortage of refrigerant charge.
• An excessive quantity of oil in the evaporator.
Waterside Tube Cleaning Procedure
Two methods are used for waterside tube cleaning to
remove scale: chemical or mechanical. The scale com-
position will determine which method is most effective
to remove the scale and dirt.
Contact a Quantech Field Service Office for a recom-
mended method that is used locally.
Chemical Cleaning Procedure
Acid Cleaning of Tubes – If the tubes are fouled with
a hard scale deposit, they may require acid cleaning.
Before acid cleaning, clean the tubes by the brushing
process described earlier. If the loose foreign material
is removed before the acid cleaning, the acid solution
will clean the tubes more efficiently, and in a shorter
amount of time.
Chemical cleaning is an effective method to remove
scale from internally enhanced copper tubes. How-
ever, a company knowledgeable with the chemical
cleaning procedure should be contracted or consulted.
Follow the chemical cleaning company guidance con-
cerning solution cleaning strength and time duration of
the cleaning process.
Commercial Acid Cleaning – If acid cleaning is re-
quired, use a commercial organization that offers a
special service to acid clean evaporators and condens-
ers, such as the Dow Industries Service Division, Dow
Chemical Co., Tulsa, OK, which has branches in prin-
cipal cities.
Serious damage to the condenser tubes
will result if the chemical cleaning pro-
cedure is improperly applied.
When chemical cleaning of the tubes is required, cal-
culate the internal volume of the waterside condenser
tubes with the following equation to properly mix the
correct concentration of cleaning solution.
Vol (gal) = [Nominal tube size (in)] x
3.14 x shell length (ft) x number of
tubes/77
Contact a Quantech Field Service Office for the size
and number of tubes.
Mechanical tube cleaning must always
follow a chemical cleaning procedure.