The pressure differential relief valve must operate to maintain the
zone between the two check valves at least 2 psi less than the
1. Close vent valve C (3).
2. Open high valve A (1).
3. Open the low valve B (2) very slowly until the differential gauge needle starts to drop.
4. Hold the valve at this position and observe the gauge reading at the moment the first discharge is
noted from the relief valve.
5. Record this as the opening differential pressure of the relief valve.
It is important that the differential gauge needle drops slowly.
To Relieve Pressure From the Test Kit
1. Close test cocks #2 (5) and #3 (6).
2. Use vent hose (blue) to relieve pressure from the test kit by opening valves A (1), B (2) and C (3).
3. Remove all test equipment and open shutoff #2 (8).