All new or modified chlorine piping systems must undergo pressure testing to verify the integrity of the piping (see section 11.4 for leak testing). ASME B31.3 (13.2.8 ), Process Piping testing requirements, should be applied as a minimum standard. There are three (3) types of acceptable testing methods:
- hydrostatic testing,
- pneumatic testing, and
- the alternate test method.
ASME Code or your company procedures should be followed for any testing that may be required for repairs and additions made after the piping system is initially tested.
Hydrostatic Testing
New chlorine piping should be hydrostatically tested to one and a half (1½) times the maximum pressure to which the system may be subjected. Pressure gauges, relief
valves, automatic control valves, and other components which may be damaged should be removed and openings should be blocked off prior to testing. After testing, all moisture-absorbing gaskets and valve packing should be replaced. It is essential that chlorine systems be thoroughly dried prior to being put into service. There are some circumstances under which drying cannot be accomplished or is not practical after hydrostatic testing with water, for these situations the pneumatic or alternate testing methods may be considered.
Pneumatic Testing
Extreme care must be used when pneumatic testing is conducted. There are numerous industry examples of high pressure pneumatic testing that resulted in the loss of life and significant destruction. For high pressure testing, the hydrostatic testing method should be used if possible. Pneumatic testing involves the hazard of released energy stored in compressed gas. The test pressure should be 110% of design pressure. The pressure should be increased until a gauge pressure which is the lesser of one half the test pressure or 25 psig is attained, at which time a preliminary leak check should be made. The pressure should be gradually increased and leak check made at intermediate pressures. It is recommended to reference ASME PCC 2 Article 5.1 (13.2.12) when conducting pneumatic testing.
Alternate Testing Method
As an alternative to pressure testing, ASME Code does allow weld examination techniques to be used. Circumferential, longitudinal, and spiral groove welds shall be
100% radiographed. All other welds shall be tested using the liquid penetrant method or the mag particle method. Additionally, the piping system must undergo flexibility analysis and sensitive leak test. The sensitive leak test is described in the ASME Boiler and Pressure Vessel Code – Section V, Article 10 (13.2.11) and involves checking for leaks of a gas such as helium. ASME Code should be referenced when using an alternate test method.