流量盤算
Flow Calculations

如何應(yīng)用流量系數(shù)
How to use Cv

　　法門流量系數(shù)(Cv)是表現(xiàn)閥門通過流體才能的數(shù)值。Cv越大，在給定壓降下閥門能夠通過的流體就越多。Cv值1表現(xiàn)當(dāng)通過壓降為1 PSI時(shí)，閥門每分鐘流過1加侖15oC的水。Cv值350表現(xiàn)當(dāng)通過壓降為1 PSI時(shí)，閥門每分鐘流過350加侖15oC的水。
　　Valve coefficient (Cv) is a number which represents a valve's ability to pass flow. The bigger the Cv, the more flow a valve can pass with a given pressure drop. A Cv of 1 means a valve will pass 1 gallon per minute (gpm) of 60oF water with a pressure drop (dp) of 1 PSI across the valve. A Cv of 350 means a valve will pass 350 gpm of 60oF water with a dp of 1 PSI.

公式1
FORMULA 1

　　流速：磅/小時(shí)(蒸汽或水)
　　FLOW RATE LBS/HR (Steam or Water)

　　

在此：
Where: dp = 壓降，單位：PSI dp = pressure drop in PSI F = 流速，單位：磅/小時(shí) F = flow rate in lbs./hr. = 比容積的平方根，單位：立方英尺/磅
(閥門下游) = square root of a specific volume in ft3/lb.
(downstream of valve)

公式2
FORMULA 2

　　流速：加倫/分鐘(水或其它液體)
　　FLOW RATE GPM (Water or other liquids)

　　

在此：
Where: dp = 壓降，單位：PSI dp = pressure drop in PSI Sg = 比重 Sg = specific gravity Q = 流速，單位：加倫/分鐘 Q = flow rate in GPM

局限性
LIMITATIONS

　　上列公式在下列條件下無效：
　　Above formulas are not valid under the following conditions:

對(duì)于可壓縮性流體，假如壓降超過進(jìn)口壓力的一半。
For compressible fluids, where pressure drop exceeds half the inlet pressure. 對(duì)于不可壓縮性流體，假如壓降產(chǎn)生空***或閃蒸。
For non-compressible fluids, where pressure drop causes cavitation or flashing. 對(duì)于雙相流體，如蒸汽-水混雜流體。
For dual-phase flow such as steam-water mixtures.

例子
EXAMPLE

通過DN350, 壓力等級(jí)Class 900的壓力密封閘閥，水溫400oF，壓力為1500 PSIG，流速為5,000,000磅/小時(shí)的壓降是多少？
What is the pressure drop through a 14" Class 900 pressure seal gate valve with 400oF water, 1500 PSIG, and 5,000,000 lbs/hr flow rate?
解：采用公式1
Solution: Use formula 1.

F = 5,000,000 = 0.137 (從水溫為400oF的表中得到) = 0.137 (from chart for water at 400oF) Cv = 9150 (來自本頁) Cv = 9150 (from page 26)

DN350 x DN300 x DN350，壓力等級(jí)Class 900縮喉管壓力密封閘閥，其它條件與例1雷同，求壓降。
What is the pressure drop through a 14"x12"x14" Class 900 Venturi pressure seal gate valve with the same conditions as example 1.
解：采用公式1
Solution: Use formula 1.
Cv = 6285 (來自本頁)
Cv = 6285 (from page 26)
溫度900oF, 壓力1200 PSI，流速500,000磅/小時(shí)的蒸汽利用中壓降小于5 PSI的壓力等級(jí)Class 2500閘閥的最小通徑是多少？
What is the smallest Class 2500 gate valve that will have less than a 5 PSI pressure drop in 900oF, 1200 PSI steam service at a flow rate of 500,000 lbs/hr?
解：采用公式1
Solution: Use formula 1.

F = 500,000 = 0.785 (來自900oF, 1200 PSIG蒸汽表) = 0.785 (from chart for steam at 900oF, 1200 PSIG) = = 2.24

　　最接近的、較大的Cv是DN250壓力等級(jí)Class 2500閘閥，其Cv是3130。這里是壓降小于5 PSIG的最小的閥門。
　　The closest higher Cv is a 10" Class 2500 gate with a Cv of 3130. This is the smallest valve with a pressure drop less than 5 PSIG.

水和蒸汽的備選特征
Selected Properties of Water and Steam 水的(下游)
For Water (Downstream) 所有壓力等級(jí)
All
Pressures 溫度(oF)
Temperature (oF) 100 200 300 400 500 600 0.127 0.129 0.132 0.137 0.143 0.154 蒸汽的(下游)
For Steam (Downstream) 壓力
PSIG
Pressure
PSIG 溫度(oF)
Temperature (oF) Sat 500 600 700 800 900 1000 1100 100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1600
1800
2000
2500
3000
4000
5000
6000 1.97
1.46
1.21
1.06
0.950
0.865
0.801
0.747
0.701
0.662
0.628
0.598
0.570
0.545 2.20
1.61
1.30
1.11
0.979
0.895 2.32
1.68
1.38
1.19
1.06
0.960
0.880
0.815
0.759
0.710
0.670
0.629
0.590
0.559 2.44
1.77
1.46
1.26
1.12
1.02
0.941
0.875
0.821
0.773
0.732
0.695
0.662
0.633
0.58
0.54
0.50
0.41
0.31
0.17
0.16
0.16 2.54
1.85
1.52
1.32
1.18
1.08
0.994
0.926
0.870
0.816
0.781
0.745
0.710
0.683
0.63
0.59
0.55
0.48
0.42
0.32
0.24
0.19 2.64
1.95
1.60
1.38
1.23
1.13
1.04
0.972
0.914
0.865
0.823
0.785
0.752
0.723
0.67
0.63
0.59
0.52
0.46
0.38
0.32
0.28 2.74
2.00
1.65
1.43
1.28
1.17
1.08
1.01
0.955
0.917
0.872
0.813
0.789
0.752
0.70
0.66
0.62
0.55
0.49
0.42
0.36
0.32 2.84
2.07
1.71
1.47
1.33
1.22
1.12
1.05
0.99
0.94
0.90
0.86
0.83
0.79
0.74
0.69
0.65
0.58
0.52
0.44
0.39
0.35

閥座端口流速盤算
Calculating Seat Port Velocity

　　下列公式可以用來盤算任何閥門的閥座流速：
　　The following formulas can be used to calculate seat port
velocity in any valve:

流量(磅/小時(shí)): 流速: (英尺/秒)= F()2 25A Flow (lbs/hr): vel: (fps) = F()2 25A 流量(加侖/分鐘): 流速: (英尺/秒)= 0.32Q A Flow (GPM): vel: (fps) = 0.32Q A

在此：
Where: F = 流量(磅/小時(shí)) F = flow (lbs/hr) = 比容積的平方根 = square root of specific volume A = 閥座端口面積 (英寸2) A = seat port area (in2) Q = 流量 (加侖/分鐘) Q = flow (gpm)

例：
　　DN300型號(hào)58809 (壓力等級(jí)Class 900)止回閥，流體介質(zhì)為溫度500 oF，壓力200 PSIG的蒸汽，流速為90,000磅/小時(shí)，求閥座端口的流速？
Example:
　　What is the seat port velocity in a 12" Figure 58809 (Class 900) check valve with a flow rate of 90,000 lbs/hr of steam at 500 oF and 200 PSIG?

解：
　　從蒸汽表得為1.61，從閥座端口面積表A得閥座端口面積為78.5英寸2。
Answer:
　　From the steam tables is 1.61, and from the seat port area table A is 78.5 in2.

流速: (英尺/秒)= F()2 25A = 90,000 (1.61)2 25 (78.5) = 118.8 英尺/秒 Vel (fps) = F()2 25A = 90,000 (1.61)2 25 (78.5) = 118.8 fps

例：
　　DN300型號(hào)180 (壓力等級(jí)150)旋啟式止回閥，流體介質(zhì)為溫度500oF，壓力200 PSIG的蒸汽，流速為90,000磅/小時(shí)，求閥座端口流速？
Example:
　　What is the seat port velocity in a 12" Figure 180 (Class 150) Swing Check Valve with a flow rate of 90,000 lbs/hr of steam at 500oF and 200 PSIG?

解：
　　查表得為1.61，A為 113.1英寸3.
Answer:
　　From the tables is 1.61 and A is 113.1 in3.

流速: (英尺/秒)= F()2 25A = 90,000 (1.61)2 25 (113.1) = 82.5英尺/秒 Vel (fps) = F()2 25A = 90,000 (1.61)2 25 (113.1) = 82.5 fps

局限性
LIMITATIONS

　　流速公式在下列條件下無效：
　　Velocity formulas are not valid under the following conditions:

對(duì)于可壓縮性流體，假如壓降超過進(jìn)口壓力的一半。
For compressible fluids, where pressure drop exceeds half the inlet pressure. 對(duì)于不可壓縮性流體，假如壓降產(chǎn)生空***或閃蒸。
For non-compressible fluids, where pressure drop causes cavitation or flashing. 對(duì)于雙相流體，如蒸汽-水混雜流體。
For dual-phase flow such as steam-water mixtures.

留心
NOTE

　　在斷定止回閥通徑時(shí)，最合適的工作流速應(yīng)當(dāng)位于這些范疇內(nèi)：
　　When determining sizing for check valves, the optimum operating velocities should fall within these ranges:

BB旋啟式止回閥：55 至115或135至240
BB截止止回閥：40 至120
PS晉升式閥瓣止回閥：55至200
PSY形止回閥：148 至200
BB Swing Check Valves - 55 to 115 or 135 to 240
BB Stop Check Valves - 40 to 120
PS Tilt Disc Check Valves - 55 to 200
PS Stop Check Valves - 40 to 180
PS Y- Stop Check Valves - 148 to 200

閥座端口面積“A”(英寸2)
實(shí)用于螺栓閥帽閥門
SEAT PORT AREA "A" FOR BOLTED
BONNET VALVES (in2) 閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 150 300 600 900 1500 11/2
2
21/2
3
4
6
8
10
12
14
16
18
20
24
30
36 1.8
3.1
4.9
7.1
12.6
28.3
50.3
78.5
113.1
137.9
182.7
233.7
291.0
424.5
671.9
969.0 1.8
3.1
4.9
7.1
12.6
28.3
50.3
78.5
113.1
137.9
182.7
227.0
283.5
424.5
672.0
942.0 1.8
3.1
–
7.1
12.6
28.3
48.7
74.7
108.4
130.2
170.9
213.8
261.6
380.1
590.9
851.2 1.8
3.1
4.9
6.5
11.8
26.0
44.2
71.0
100.0
117.9
–
–
–
–
–
– 1.5
2.8
4.0
6.0
10.3
22.7
38.5
60.0
84.5
101.6
–
–
–
–
–
–

閥座端口面積(英寸2)
實(shí)用于壓力密封閘閥，截止閥，晉升式閥瓣止回閥
SEAT PORT AREA FOR PRESSURE SEAL GATE,
GLOBE, TILT DISC CHECK VALVES (in2)

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 600 900 1500 2500 21/2
3
4
6
8
10
12
14
16
18
20
24 5.4
5.4
9.6
23.2
39.9
61.0
88.7
–
–
173.8
–
310.25 5.9
5.9
10.3
21.7
37.7
58.4
80.5
97.2
125.2
156.7
198.0
287.3 3.3
4.9
8.3
18.9
31.9
48.7
69.0
82.5
108.4
137.9
170.9
247.5 2.4
3.6
5.9
12.6
21.7
34.5
47.2
58.2
76.6
97.2
117.9
170.9

閥座端口面積(英寸2)
實(shí)用于壓力密封Y形截止閥
SEAT PORT AREA FOR PRESSURE SEAL Y-GLOBE
VALVES (in2)

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 900 1500 2500 8
10
12
14
16
18
20
24 39.9
61.9
86.6
86.6
135.4
135.4
198.1
302.6 39.9
61.9
86.6
86.6
135.4
135.4
198.1
302.6 27.2
42.8
60.1
86.6
86.6
135.4
135.4
198.1 螺栓閥帽閘閥全開狀態(tài)下的流量系數(shù)Cv
Bolted Bonnet
Gate Valves FULL OPEN Cv 閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 150 300 600 900 1500 11/2
2
21/2
3
4
5
6
8
10
12
14
16
18
20
24
30
36 165
307
490
710
1300
2090
3110
5720
8935
13350
16275
21560
28720
35760
52165
86235
129500 165
307
490
710
1300
–
3110
5720
8935
13350
16275
21560
27890
34840
51050
84765
125825 165
307
490
710
1300
–
3110
5540
8495
12800
15370
29170
26270
32140
46710
75530
114250 –
–
–
650
1220
–
2850
5025
7850
11475
13910
–
–
–
–
–
– 138
270
400
600
1070
1600
2500
4375
6840
9980
12000
–
–
–
–
–
– 圖1
螺栓閥帽截止閥
Figure 1
Bolted Bonnet
Globe Valves
(1)當(dāng)開啟度小于
10%時(shí)，不建議
用于節(jié)流暢用。
(1) not recommended for
throttling at less
than 10% Open.

壓力密封閘閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal
Gate Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 600 900 1500 2500 21/2
3
4
6
8
10
12
14
16
18
20
24 350
525
925
2150
3775
5750
8600
10275
13425
17200
20950
30850 350
450
850
1925
3575
5250
7550
9150
11950
15575
19200
27675 275
415
730
1675
2925
4550
6570
7890
10325
13425
16825
24150 190
275
460
1100
1970
3130
4535
5500
7210
9215
11450
16575

壓力密封縮喉管閘閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal
Venturi Gate Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 600 900 1500 2500 8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16
18 x 16 x 18
20 x 18 x 20
22 x 20 x 22
26 x 24 x 26 1570
2795
4485
7310
9000
11000
14200
16800
25000 1385
2385
4065
6285
7200
9760
12185
16005
23000 1185
2155
3450
5640
6270
8465
11120
14130
– 815
1430
2515
3855
4415
6165
7960
9645
– 螺栓閥蓋旋啟式止回閥全開狀態(tài)下的流量系數(shù)Cv
Bolted Cap
Swing Check Valves FULL OPEN Cv 閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 150 300 600 900 1500 11/2
2
21/2
3
4
6
8
10
12
14
16
18
20
24
30 63
142
217
356
716
1414
2961
5720
7860
10416
13800
13420
16708
33384
54556 63
168
275
392
740
1992
2340
5720
8544
19464
13800
13029
16276
36672
54652 97
139
227
246
499
1334
3359
5440
7045
9840
12912
–
19540
–
– –
–
–
358
605
1623
2508
4069
6316
–
–
–
–
–
– –
111
–
315
564
1520
–
–
–
–
–
–
–
–
–

螺栓閥帽截止閥全開狀態(tài)下的流量系數(shù)Cv
Bolted Bonnet
Globe Valves FULL OPEN Cv

閥門
通徑
Valve Size 壓力等級(jí)
Pressure Class 150 300 600 900 塞形
或
球形
閥瓣
Plug or
Ball
Disc V形
端口
閥瓣
V-Port
Disc 塞形
或
球形
閥瓣
Plug or
Ball
Disc V形
端口
閥瓣
V-Port
Disc 塞形
或
球形
閥瓣
Plug or
Ball
Disc V形
端口
閥瓣
V-Port
Disc 塞形
或
球形
閥瓣
Plug or
Ball
Disc 11/2
2
21/2
3
4
5
6
8
10
12 23
43
70
100
185
297
440
810
1260
1890 –
40
–
92
170
273
405
745
1150
– 23
43
70
100
185
–
440
810
1260
1890 21
40
–
92
170
–
405
745
–
– 23
43
70
100
185
–
440
780
–
1810 –
40
–
92
170
–
405
–
–
– –
–
–
90
170
–
–
–
–
–

壓力密封晉升式閥瓣止回閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal
Tilting Disc Check Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 900 1500 2500 21/2
3
4
6
8
10
12
14
16
18
20
24 95
146
268
627
1062
1722
2420
2955
3945
4900
6275
9295 80
132
230
536
940
1465
2110
2550
3395
4365
5465
8060 60
94
146
355
627
1020
1420
1775
2355
3025
3705
5465

壓力密封縮喉管晉升式閥瓣止回閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal
Venturi Tilting Disc Check Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 150 300 600 8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16
18 x 16 x 18
20 x 18 x 20
22 x 20 x 22 565
955
1550
2175
2660
3550
4410
5650 480
845
1320
1900
2295
3055
3930
4920 320
565
920
1275
1598
2120
2725
3335

球形止回閥，截止止回閥，晉升式止回閥的流量特征曲線
Characteristic Flow Curves for Globe Stop, Stop-Check, Lift-Check Valves

小于全開狀態(tài)的估計(jì)流量系數(shù)Cv
Estimating Cv For Less Than Fully Open Valves

圖2
球形止回閥，截止止回閥和晉升式止回閥
Figure 2
Globe Stop, Stop-Check and
Lift-Check Valves

壓力密封T形球形止回閥，截止止回閥和晉升式止回閥
閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal T-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv 閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 900 1500 2500 21/2
3
4
6
8
10
12
14 90
105
195
455
800
1250
1820
2205 65
95
170
395
695
1085
1580
– 45
65
105
265
470
750
1100
–

壓力密封Y球形止回閥，截止止回閥和晉升式止回閥
閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal Y-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 600 900 1500 2500 8
10
12
14
16
18
20
24 2025
3025
4600
4300
7650
7325
11800
16450 1750
2725
3825
3650
6000
5825
9125
13500 1750
2725
3825
3650
6000
5825
9125
13500 1175
1875
2650
4075
3775
6625
6225
9050

　　表中所列流量系數(shù)僅實(shí)用于全開狀態(tài)下的閥門。不是全開狀態(tài)的流量系數(shù)可以采用實(shí)用于晉升式閥瓣止回閥和截止閥的流量特征曲線進(jìn)行估算。不建議將閘閥用在節(jié)流暢用中。
　　The flow coefficient (Cv) listed in the tables apply to fully open valves only. Flow coefficients at other than fully open may be approximated by use of the characteristic flow curves for tilting disc check and globe valves. Gate valves are not recommended for throttling service.

例：
　　DN300，壓力等級(jí)Class 900的美國太平洋壓力密封截止閥在開心胸為1/4時(shí)的流量系數(shù)是多少？
EXAMPLE:
　　What is the Cv of a 12 inch Class 900 Pacific pressure seal globe valve 1/4 open?

圖3
Y形球形止回閥，截止止回閥和晉升式止回閥
Figure 3
Y-Globe Stop, Stop-Check and
Lift-Check Valves

壓力密封縮喉管球形止回閥，截止止回閥和晉升式止回閥
閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal Venturi Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv 閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 900 1500 2500 8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16 450
770
1215
1775
2125 390
690
1055
1550
– 260
465
745
1070
–

壓力密封縮喉管Y球形止回閥，截止止回閥和晉升式止回閥
閥全開狀態(tài)下的流量系數(shù)Cv
Pressure Seal Venturi Y-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

閥門通徑
Valve Size 壓力等級(jí)
Pressure Class 600 900 1500 2500 8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16
18 x 16 x 18
20 x 18 x 20
22 x 20 x 22
16 x 24 x 26 1100
1925
2875
4375
4075
7250
6950
11200
15850 1000
1675
2600
3650
3450
5700
5525
8675
12825 1000
1675
2600
3650
3450
5700
5525
8675
12825 650
1125
1775
2525
3875
3575
6300
5925
8600

解：
　　從上列流量系數(shù)表中得到，DN300，壓力等級(jí)Class 900截止閥在全開狀態(tài)下的Cv是1820。
SOLUTION:
　　From the flow coefficient table above, the fully open Cv for a 12 inch, Class 900 globe valve is 1820.

　　查詢圖2，全開狀態(tài)的1/4時(shí)閥門的比率是52%.
　　Consulting Figure 2, the percent of fully open Cv at 1/4 valve open is 52%.

　　因此盤算1/4全開的流量系數(shù)Cv為：
　　0.52 x 1820 = 946.
　　The Cv at 1/4 open is then computed as:
　　0.52 x 1820 = 946.