CVS Controls 128PQC Series Manual de instruções - Página 4
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Maintenance
Warning:
Prior to performing any maintenance, isolate
the valve from the process pressure. Vent
control input signal pressure. Relieve the
process pressure and drain process media
from both sides of valve (Figure 5, Key 27). A
sudden release of pressure or fluid can cause
personal injury or property damage.
Scheduled inspections and maintenance are
vital to continued operation of all pressure
control valves and systems. Parts are subject
to wear and tear, and must be replaced as
necessary, depending on the intensity of service
conditions. Unless the valve body requires
maintenance or replacement, it may remain in
the pressure system or on the vessel.
Table 2: Maximum Allowable Shutoff Pressure Drops
Flowing
Pressure
Actuator
Seating
Drop
Action
Tends
To:
Open
Valve
Fail
Close
Metal
Close
(All
Valve
Types)
Fail
Close
Open
Valve
Open
Valve
Fail
Close
Close
Soft
Valve
Fail
Close
Open
Valve
* Contact CVS Controls for pressure drop
4
Port
Cadmium Coloured Main Spring
Diameter
CVS14A8831X012
At 20 Psig (1.4
bar) Operating
Signal Pressure
In
mm
(2 Springs Req'd)
Psi
Bar
1/4
6.4
1510
104
3/8
9.5
520
36
1/2
12.7
220
15
1/4
6.4
940
65
3/8
9.5
1130
78
1/2
12.7
1330
92
1/4
6.4
170
12
3/8
9.5
530
36
1/2
12.7
540
37
1/4
6.4
1000
69
3/8
9.5
710
49
1/2
12.7
400
28
1/4
6.4
940
65
3/8
9.5
1000
69
1/2
12.7
1000
69
1/4
6.4
560
39
3/8
9.5
480
33
1/2
12.7
540
37
Replacing Packing and Trim
Follow these procedures when replacing the
entire packing and trim assembly or individually
replacing packing and trim parts. Unless
otherwise indicated, key numbers in this section
reference Table 3 for parts listings for
replacement packing and trim assembly, Figure
3 for packing and trim assembly key numbers
and Figure 5 control valve assembly key
numbers.
1. Detach the control valve from all pressure,
and release pressure from valve body and
actuator. Ensure the valve is completely
closed.
2. Remove the four nuts (Key 32) from the
screws of the lower diaphragm casing. After
disconnecting the input signal tubing,
remove the actuator from the valve body,
along with attached trim parts.
At 35 Psig (2.4
At 20 Psig (1.4
bar) Operating
bar) Operating
Signal Pressure
Signal Pressure
(4 Springs Req'd)
(2 Springs Req'd)
Psi
Bar
Psi
3370
232
3380
1340
92
1340
690
47
700
1860
128
1370
2450
169
1540
2920
201
1710
350
24
---
610
42
---
1150
79
---
1000
69
1000
1000
69
1000
830
57
830
1000
69
1000
1000
69
1000
1000
69
1000
660
45
---
960
66
---
1000
69
---
Red Main Spring
CVS14A9077X012
At 35 Psig (2.4
bar) Operating
Signal Pressure
(4 Springs Req'd)
Bar
Psi
Bar
233
3600
248
92
3120
215
48
1720
118
94
2920
201
106
3300
227
118
3600
248
---
---
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---
---
---
---
---
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69
1000
69
69
1000
69
57
1000
69
69
1000
69
69
1000
69
69
1000
69
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