Service manual

6-- 12T--318
6. Allow the Oakite No. 32 solution to soak in the tube
coils for several hours, periodically pump-circulating
it with an acid-proof pump.
An alternate method may be used whereby a pail (see
Figure 6-18) filled with the solution and attached to
the coils by a hose can serve the same purpose by fill-
ing and draining. The solution must contact the scale
at every point for thorough de-scaling. Air pockets in
the solution should be avoided by regularly opening
the vent to release gas. Keep flames away from the
vent gases.
Fill condenser with clean-
ing solution. Do not add
solution more rapidly than
vent can exhaust gases
caused by chemical
action.
Condenser
Vent
pipe
1” Pipe
5’ Approximate
3’ to 4’
Figure 6-18 Water Cooled Condenser Cleaning -
Gravity Circulation
7. The time required for de-scaling will vary, depending
upon the extent of the deposits. One way to deter-
mine when de-scaling has been completed is to
titrate the solution periodically, using titrating equip-
ment provided free by the Oakite Technical Service
representative. As scale is being dissolved, titrate
readings will indicate that the Oakite No. 32 solution
is losing strength. When the reading remains
constant for a reasonable time, this is an indication
that scale has been dissolved.
8. When de-scaling is complete, drain the solution and
flush thoroughly with water.
9. Following the water flush, circulate a 56.7 gram (2
ounce) per 3.785 liter (1 U.S. gallon) solution of
Oakite No. 22 thru the tubes to neutralize. Drain this
solution.
10.Flush the tubes thoroughly with fresh water .
NOTE
If the condenser cooling water is not being used
as drinking water or is not re-circulated in a
closed or tower system, neutralizing is not nec-
essary.
11. Put the unit back in service and operate under nor-
mal load. Check the head pressure. If normal, a thor-
ough de-scaling has been achieved.
For Additional Help:
Contact the Engineering and Service Department of
Chemetall Oakite, 675 Central Avenue, New
Providence, NJ 07974 for the name and address of the
service representative in your area, or visit the
company’s Web site (www.oakite.com).
6.13 FILTER-DRIER
On units equipped with a water-cooled condenser , if the
sight glass appears to be flashing or bubbles are
constantly moving through the sight glass when the
suction modulation valve is fully open, the unit may have
a low refrigerant charge or the filter-drier could be
partially plugged.
a. To Check Filter-Drier:
1. Test for a restricted or plugged filter-drier by feeling
the liquid line inlet and outlet connections of the drier
cartridge. If the outlet side feels cooler than the inlet
side, then the filter-drier should be changed.
2. Check the moisture-liquid indicator if the indicator
shows a high level of moisture, the filter-drier should
be replaced.
b. To Replace Filter-Drier:
1. Pump down the unit (refer to paragraph 6.4 and
replace filter-drier.
2. Evacuate the low side in accordance with paragraph
6.6.
3. After unit is in operation, inspect for moisture in sys-
tem and check charge.
6.14 THERMOSTATIC EXPANSION VALVE
The thermostatic expansion valve (see Figure 2-2) is an
automatic device that maintains constant superheat of
the refrigerant gas leaving the evaporator , regardless of
suction pressure.
The valve functions are:
1. Automatic control of the refrigerant flow to match the
evaporator load.
2. Prevention of liquid refrigerant entering the com-
pressor.
Unless the valve is defective, it seldom requires
maintenance other than periodic inspection to ensure
that the thermal bulb is tightly secured and properly
insulated. See Figure 6-19.
NOTE
TXV Bulb Clamp is soldered to the suction line.