Boiler house Level controls
2
For alternative sizes to the standard DN40 (1½")
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)
Valve stem seals are available in normal (PTFE) or high temperature (graphite) material. We recommend the use of the high temperature seal to decrease the possibility of leakage over long term use. Valves with high temperature stem seals are suffixed 'H'.
2.3 90
3. Selection of the valve Kv 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 is on page 6
TI-S75-11 EMM Issue 5
Page 4 of 7
Selection of Modulating Feedwater Valves Electrically Actuated
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