Boiler house Level controls
2
2. Selection of the valve body material and pressure rating The valve body must be suitable for the maximum pressure and temperature in the feedwater line. Standard valve types are as follows:
KE71
Screwed
SG iron body
PN25 rating (Pmax 25 bar g at 120 ºC)
KE73
Flanged
KE43
Cast steel body
Flanged PN40 rating (Pmax 40 bar g at 50 ºC)
3. Selection of the valve Kv The DN40 valve body size is available with various seat sizes giving a choice of Kv values. Use the graph to select a suitable Kv as follows: a) The feedwater flowrate is the actual maximum steam generation rate of the boiler plus any blowdown rate where this is significant. In practice the use of the 'from and at' boiler rating will give a small safety margin. In the example this is 15 000 kg/h. b) The pressure drop across the valve is the feedpump pressure at the maximum flowrate, minus the boiler pressure, minus any valve and pipework losses. In the example the available pressure drop is 1.5 bar. c) Select the larger Kv value, 16 in this example. If right on the line, or if in doubt, select a larger Kv. 4. Selection of the actuator + valve adaptor The actuator has to be capable of shutting off against the maximum feedpump pressure when the boiler is not under pressure. Select the actuator from the table below: Metal seat (T, S or W) PEEK seat (P or C) At Feedwater temperature >50°C body rating must be considered Feedwater temperature ≤100 °C Feedwater temperature >100 °C
2.3 88
AEL72211JXA (0.4 mm/s) AEL72211GXA (0.4 mm/s) AEL72213FXA (0.4 mm/s)
220/240 Vac AEL73221JXA
AEL73221JXA
AEL72211JXA (0.4mm/s)
110 Vac AEL73222GXA
AEL73222GXA
AEL72211GXA (0.4mm/s)
Actuator type
24 Vac AEL73223FXA
AEL73223FXA
AEL72213FXA (0.4mm/s)
24 Vdc AEL73224KXA AEL72224KXA
AEL73224KXA
AEL72224KXA
Size
Kv value
Maximum feedpump pressure bar g
25.0
37.1
(33.8)
15.0
(33.8)
18.6
(15.3)
16.0
(33.0)
40.0
(40.0)
DN40 Valve Size
10.0
40.0
(40.0)
40.0
19.0
(19.0)
(40.0)
6.3
N/A
N/A
Auxiliary switch
AEL7X010
Valve adaptor
Integral
Mounting flange
EL5970
Spindle speed 0.8mm/s unless otherwise stated Figures in brackets denotes the differential pressures for valves fitted with high temperature graphite stem sealing. These valves have a suffix 'H'. Valve stroke is 20 mm.
TI-S75-11 EMM Issue 5
Page 2 of 7
Selection of Modulating Feedwater Valves Electrically Actuated
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