Carrier AquaForce B Series - Page 72

72
EVAPORATOR RETUBING
When retubing is required, obtain the service of qualified per-
sonnel experienced in boiler maintenance and repair. Most
standard procedures can be followed when retubing the evapo-
rators. An 8% crush is recommended when rolling replacement
tubes into the tube sheet. Place one drop of Loctite No. 675 or
equivalent on top of tube prior to rolling. This material is in-
tended to “wick” into the area of the tube that is not rolled into
the tube sheet, and prevent fluid from accumulating between
the tube and the tube sheet. New tubes must also be rolled into
the center tube sheet to prevent circuit to circuit leaks.
TIGHTENING EVAPORATOR HEAD BOLTS
Preparation
When reassembling evaporator heads, always check the condi-
tion of the O-rings first. The O-ring should be replaced if there
are visible signs of deterioration, cuts or damage. Apply a thin
film of grease to the O-ring before installation. This will aid in
holding the O-ring in the groove while the head is installed.
Torque all bolts to the following specification and in sequence:
5
/
8
-in. Diameter Perimeter Bolts (Grade 5). . . . 150 to 170 ft-lb
(203 to 230 N-m)
3
/
4
-in. Diameter Perimeter Bolts (Grade 5). . . . 200 to 225 ft-lb
(271 to 305 N-m)
1. Install all bolts finger tight.
2. Bolt tightening sequence is outlined in Fig. 69. Follow the
numbering or lettering sequence so that pressure is evenly
applied to O-ring.
3. Apply torque in one-third steps until required torque is
reached. Load all bolts to each one-third step before pro-
ceeding to next one-third step.
4. No less than one hour later, retighten all bolts to required
torque values.
5. After refrigerant is restored to system, check for refrigerant
leaks using recommended industry practices.
6. Replace evaporator insulation.
INSPECTING/CLEANING HEAT EXCHANGERS
Inspect and clean evaporator tubes at the end of the first operat-
ing season. Because these tubes have internal ridges, a rotary-
type tube cleaning system is necessary to fully clean the tubes.
Tube condition in the evaporator will determine the scheduled
frequency for cleaning, and will indicate whether water treat-
ment is adequate in the chilled water/brine circuit. Inspect the
entering and leaving water thermistor wells for signs of corro-
sion or scale. Replace the well if corroded or remove any scale
if found.
Fig. 69 — Flooded Evaporator Unit Head Recommended Bolt Torque Sequence
CAUTION
Hard scale may require chemical treatment for its preven-
tion or removal. Consult a water treatment specialist for
proper treatment procedures.
4
2
6
10
14
18
23
21
17
15
11
7
3
1
5
9
13
17
19
24
22
16
12
8
4
2
6
10
14
15
11
7
3
1
5
9
13
16
12
8
24" EVAPORATOR – 5/8" BOLTS
(30XA350M THRU 30XA500M)
20" & 18" EVAPORATOR – 3/4" BOLTS
(30XA200M THRU 30XA350S)
4
2
6
10
11
7
3
1
5
9
12
8
16" EVAPORATOR – 3/4" BOLTS
(30XA160M THRU 30XA200S)
4
2
6
10
14
11
7
3
1
5
9
13
12
8
14" EVAPORATOR – 3/4" BOLTS
(30XA140S THRU 30XA160S)