Control systems Pressure reducing/surplussing valves
4
Capacities for safety valve sizing
DN15 (½")
DN20 (¾")
DN25 (1")
Size
For conversions: Cv (UK) = Kv x 0.963 Cv (US) = Kv x 1.156
Full lift capacities for safety valve sizing purposes :
Kv
1.5
2.5
3.0
Steam and compressed air capacities
10 (150)
11 (165)
12 (180)
13 (205)
17 (245)
8.6 (125)
8 (120)
8 (120)
7 (105)
7 (105)
6 (90)
6 (90)
5 (75)
5 (75)
4 (60)
4.6 17
4 (60)
Upstream pressure bar g (psi g) (x 100 = kPa)
3 (45)
3 (45)
2 (30)
2 (30)
1 (15)
Steam capacity kg/h
40
80
120
160
200
240
280
½" - DN15
(88)
(176)
(265)
(353)
(441)
(529)
(617)
50
100
150
200
250
300
350
¾" - DN20
(110)
(220)
(330)
(441)
(551)
(661)
(772)
70
140
210
280
350
420
490
1" - DN25
(154)
(309)
(463)
(617)
(771)
(926)
(1080)
Compressed air capacity dm 3 /s * free air
10
20
30
40
50
60
70
80
90
100
½" - DN15
(21)
(42)
(64)
(85)
(106)
(127)
(148)
(170)
(191)
(212)
10
20
30
40
50
60
70
80
90
100
110
120
¾" - DN20
(21)
(42)
(64)
(85)
(106)
(127)
(148) (170)
(191) (212)
(233) (254)
20
40
60
80
100
120
140
160
180
1" - DN25
* dm 3 /s = I/s, 1 I/s d 2 c.f.m.
(42)
(85)
(127)
(170)
(212)
(254)
(297)
(339)
(381)
How to use the chart The curved lines labelled 2, 3, 4, 5 etc., represent upstream pressures. Downstream pressures are read along the vertical line on the left hand side of the chart. How to use the chart is best described by an example:- Required, a pressure reducing valve to pass 120 kg/h reducing from 8 to 6 bar. From the downstream pressure of 6 bar on the left hand side of the chart extend out horizontally until the line meets the curved 8 bar upstream line. At this point read vertically downwards where it will be seen that a ½ " SRV2S will be required.
TI-P186-05 CTLS Issue 9
Page 5 of 7
SRV2S Stainless Steel Pressure Reducing Valve
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