070.610-IOM (JUL 21)
Page 45
RWF II Rotary Screw Compressor Units
Maintenance
The spring is compressed with a large bolt (7). If it is nec
-
essary to repair the valve, it can be dismantled as follows:
1. To manually open the valve, mount the hexagon screw
(29), the hexagon flange nut (28) and the nylon ring (27) as
shown. Tighten the nut (28) a few turns, in order to redraw
the valve cone from the seat.
NOTICE
Step 1 is not strictly necessary when dismantling the
valve, but will prevent the valve seat gasket from
being exposed to a shear load, and it will keep all
internal valve parts together as a unit.
2. Loosen the screws (24) by 0.315 in (8 mm), and ensure
that the bonnet (2) is not under pressure from the spring.
If the bonnet is under pressure from the spring
(15)
after all the screws have been loosened by 0.315 in (8
mm), there is a damage inside the valve. In this case, it is
important to remove only two screws, one from each side.
In the threaded holes from which the two screws have
been removed, insert studs with nuts (see table for size)
and turn the nuts down to meet the bonnet (2). Studs
must be about the same length as the
valve body. Then
remove the remaining two screws (24), loosen the nuts on
the studs, and carefully ease off the bonnet. All internal
parts can then be safely removed.
NOTICE
If step 1 was followed, loosen the hexagon nut (28)
carefully, holding the hexagon screw (29) in place.
If the bonnet is not under pressure from the spring
, all
screws (24) can be removed. The bonnet and all internal
parts can now be removed from the valve body.
When internal parts have been taken out of the valve
body, the spring can be removed by unscrewing the spring
bolt (7).
NOTICE
When assembling the valve, the bonnet gasket (17)
must be captured in the groove in the bonnet (2).
After the bonnet assembly is mounted into the valve
housing (1), install and tighten bonnet cap screws (24). The
required torque is shown for each valve size in the table
below.
Table 17: Bonnet cap screw torque values
Valve
Torque
(N.m)
Valve
Torque
(lb-ft)
Screw
size
size
size
DN (mm)
ANSI (in.)
(mm)
65
74
2 1/2
54
M12
80
44
3
32
M10
100
74
4
54
M12
125
183
5
134
M16
150
183
6
134
M16
200
370
8
271
M20
those items that might relate to the symptom. Use the list
as a guide to further investi gate the problem.
The second step in problem solving is to decide which
items on the list are possible causes and which items are
additional symptoms. High discharge temperature and high
oil temperature readings on a display may both be symp
-
toms of a problem and not casually relat ed. High suction
superheat or a low receiver level, however, could cause
both symptoms.
The third step is to identify the most likely cause and take
action to correct the problem. If the symptoms are not
relieved move to the next item on the list and repeat the
procedure until you have identified the cause of the prob
-
lem. Once the cause has been identi fied and con firmed
make the necessary correc tions.
Servicing the cold-start valve
Figure 47: Cold-start valve
Before beginning to disassemble the valve, the refrigerant
must be removed from all associated piping.
Start room ventilation and put on a safety mask.
WARNING
Be extremely careful when dismantling the cold-start
valve on the discharge side of the unit, as condensed
refrigerant often is trapped between the cold-start
valve and the stop valve. A bleed valve on the side
of the check valve is used to vent the space between
the check valve and stop valve. Exposure to refriger-
ant fumes can cause injury or death.
WARNING
Inside the valve (see
) there is a very heavy,
tight spring (15). Provided the valve is intact, the
spring presents no danger when dismantling.
