Control systems Pressure reducing/surplussing valves
4
Sizing The required Kv can be calculated from the following formulae: where: = Steam mass flow (kg/h) = Liquid volume flow (m 3 /h) = Gas flow at standard conditions: 0 °C @ 1.013 bar a (m 3 /h)
P 1 = Upstream pressure (bar absolute) P 2 = Downstream pressure (bar absolute)
P 1 - P 2
c =
(pressure drop factor)
P 1 S = Specific gravity T =
Absolute average gas temperature (Kelvin = °C + 273)
Critical pressure drop: P 2 ≤ 0.58 P 1
4.6 143
Steam
Non-critical pressure drop: P 2 ≥ 0.58 P 1
Gas
Liquid
Calculating the Kv and selecting a suitable valve Using your maximum flowrate and smallest differential pressure (P 1 – P 2 ), calculate the required Kv from one of the above formulae. Select a valve Kv that is 30% greater than the calculated Kv. The optimum working range of the selected valve should ideally be within the range of 10 to 70% of its Kv value.
Recommended fluid velocities
Saturated
10 to 40 m/s (32.8 to 131.2 ft/s)
Steam
Superheated
15 to 60 m/s (49.2 to 196.9 ft/s)
up to 2 bar g (29 psi g)
2 to 10 m/s (6.6 to 32.8 ft/s)
Gas
above 2 bar g (29 psi g)
5 to 40 m/s (16.4 to 131.2 ft/s)
Liquids
1 to 5 m/s (3.28 to 16.4 ft/s)
TI-P186-08 CTLS Issue 19
Page 3 of 5
SRV66 Sanitary Pressure Reducing Valve
Powered by FlippingBook