Leak testing should be done once the piping system is completely assembled. The purpose of a leak test is to ensure all connections and components will not leak chlorine when pressurized. Leak testing is not a substitute for pressure testing. If the system was not disassembled and reassembled as part of the pressure testing and drying process, the nitrogen/dry air test (i.e. Step 1) may be omitted.
Step 1
Pressurize the system to the lower of 150 psig (1034 kPA) or to the normal operating pressure with dry air or nitrogen. Use a soap solution to test for leaks at joints. If leaks are found, make the necessary repairs and repeat this step. If no leaks are found, vent the dry air/nitrogen from the system down to approximately 2 psig.
Do NOT allow the system to get wet by pulling in atmospheric air.
Step 2
Introduce chlorine gas (NEVER liquid chlorine) into the system and raise the pressure to approximately 5 psig. Consider using a dilute chlorine stream, such as a mixture of chlorine and nitrogen when beginning this process.
Step 3
Test the system for leaks.
Care must be taken that chlorine has diffused throughout the piping system before leak checking with ammonia. The location of a leak in a chlorine containing system can usually be detected by the reaction of ammonia vapor with the escaping chlorine. The reaction produces a dense white cloud. The most convenient way is to use 5-30% aqua ammonia (10.3-61.7% ammonium hydroxide) solution vapors in a squeeze bottle. Direct the vapors at the suspected leak. Do not squirt liquid aqua ammonia on pipe fittings to prevent corroding carbon steel.
NEVER attempt to repair leaks by welding until all chlorine has been purged from the system. When detectable leaks have been repaired, the line should be retested by
repeating Step 1.
Any effort to detect the source of a chlorine leak should be carried out with full consideration for potential hazards. Appropriate protective equipment must be used;
reference Cl Pamphlet 65 (13.1).
NOTE: When ammonia (NH3) is dissolved in water it forms ammonium hydroxide (NH40H). Aqua ammonia is a common name for ammonium hydroxide solution but only represents the NH3 portion of the NH4QH in solution. Therefore, aqua ammonia (MW=17.03) is ~50% (48.6%) of the ammonium hydroxide (MW=35.05) concentration based on molecular weights.
Step 4
Slowly increase the chlorine pressure and continue to check for leaks at several intermediate pressures until the operating pressure is obtained. Consider using a dilute
chlorine stream, such as a mixture of chlorine and nitrogen when beginning this process. If flange leaks are detected, tighten the flange and continue Step 4 until the operating pressure is achieved.