
Bulletin 71.2:LR125
6
Table 5. Main Valve Minimum Differential Pressures
(1)
MAIN VALVE
BODY SIZE
DIAPHRAGM
MINIMUM DIFFERENTIAL, PERCENT OF CAPACITY
For 90% Capacity For 100% Capacity
In. DN Diaphragm Code Diaphragm Material psid bar d psid bar d
1 25
17E68 (standard) Nitrile (NBR), Low Minimum Differential 30 2.1 30 2.1
17E97 Nitrile (NBR), High Erosion Resistance 35 2.5 35 2.5
17E88 Fluorocarbon (FKM), High Temperature Capability 30 2.1 30 2.1
2 50
17E68 (standard) Nitrile (NBR), Low Minimum Differential 18 1.2 19 1.3
17E97 Nitrile (NBR), High Erosion Resistance 24 1.7 24 1.7
17E88 Fluorocarbon (FKM), High Temperature Capability 18 1.2 19 1.3
3 80
17E68 (standard) Nitrile (NBR), Low Minimum Differential 21 1.5 28 1.9
17E97 Nitrile (NBR), High Erosion Resistance 23 1.6 23 1.6
17E88 Fluorocarbon (FKM), High Temperature Capability 21 1.5 28 1.9
4 100
17E68 (standard) Nitrile (NBR), Low Minimum Differential 16 1.1 30 2.1
17E97 Nitrile (NBR), High Erosion Resistance 16 1.1 34 2.3
17E88 Fluorocarbon (FKM), High Temperature Capability 16 1.1 30 2.1
1. See Table 1 for structural design ratings and Table 2 for Type MR95H pilot rating.
Figure 4. Cavitation Sizing for Water
Table 6. Flow and Sizing Coef cients for Type LR125 Main Valve at 100% Capacity
MAIN VALVE BODY SIZE REGULATING COEFFICIENTS WIDE-OPEN COEFFICIENTS
K
m
IEC SIZING COEFFICIENTS
In. DN C
V
C
1
C
V
C
1
X
T
F
D
F
L
1 25 14.8 33.4 15.2 33.5 0.88 0.706 0.06 0.94
2 50 50.8 37.2 52.4 37.2 0.92 0.875 0.09 0.96
3 80 91.4 38.8 94.1 38.8 0.94 0.952 0.09 0.97
4 100 147 38.7 151 38.7 0.85 0.947 0.09 0.92
CAVITATION PREDICTION
CONTINUOUS SERVICE REGION
INTERMITTENT SERVICE REGION
FULL CAVITATION REGION
0
OUTLET PRESSURE (P2)
psig / bar
INLET PRESSURE (P1)
psig / bar
150 /
10.3
300 /
20.7
270 /
18.6
240 /
16.5
210 /
14.5
180 /
12.4
150 /
10.3
120 /
8.3
135 /
9.3
120 /
8.3
105 /
7.2
90 /
6.2
90 /
6.2
75 /
5.2
60 /
4.1
60 /
4.1
45 /
3.1
30 /
2.1
30 /
2.1
15 /
1.0
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