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Relief Valves

RELIEF VALVE DIMENSIONS

VALVE SIZE

AA

BB

CC

INLET SIZE

OUTLET SIZE

1/2"

5 13/16

2 1/8

1 9/32

1/2"

3/4"

3/4"

5 15/16

2 5/16

1 13/32

3/4"

1"

1"

6 31/32

2 27/32

1 3/4

1"

1 1/4"

1 1/4”

8 5/16

3 1/2

2

1 1/4"

1 1/2”

1 1/2”

9 1/2

3 5/8

2 3/16

1 1/2”

2”

Regenerative Turbine Pumps should never be operated at no-flow, or “shut-off” conditions. In systems where pumps may exceed the pump or system design operating pressure, it is highly recommended that a Pressure Relief Valve or other protective device be installed in the discharge line. This will relieve excess pressure and prevent motor overload or pump failure in the event of restricted flow conditions. Another more sophisticated option is to use a VFD (variable frequency drive) with a closed-loop pressure transducer feedback loop. This equipment will allow the automatic adjustment and limiting of motor RPM to maintain a given pressure. MTH provides both relief valves and VFD’s for use with its pumps, as optional purchased accessories.

Relief Valve Sizing

  1. Add 10 PSI (23') to customer specified operating head and locate on pump curve. Log capacity and BHP from this point. Check to be sure motor horsepower is large enough to handle this head.
  2. Convert head to PSI and add to pump suction pressure to determine PRV setting.
  3. Go to PRV flow/pressure chart to select size of valve necessary.

Series 78-79 Brass Valves

Water Capacity in Gallons per minute (GPM) at 25% Over Pressure

SET
PRESSURE
SEAT SIZE - Inches
1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3
5 2.8 3.9 7.7 12 17 22 33 44
10 3.9 5.6 8.1 17 24 31 46 62
15 4.8 6.8 13 21 29 38 56 76
20 5.5 7.9 15 24 34 44 65 88
25 6.2 8.8 17 27 38 49 73 98
30 6.8 9.7 19 29 41 53 80 107
40 7.7 11 22 34 48 62 92 124
50 8.4 12 24 38 53 69 103 139
75 10.5 15 30 47 65 85 126 170
100 12 18 34 54 76 98 146 196
110 13.3 19 36 56 79 102 153 206
125 14 20 38 60 85 109 163 219
150 15.4 22 42 66 93 120 178 240
175 16.1 23 45 71 100 129 193 259
200 17.5 25 48 76 107 138 206 277
250 19.6 28 54 85 120 154 230 310
300 21.7 31 59 93 131 169 252 340

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