Process Piping Case History
An oxygen line with down legs in Michigan required preoperative cleaning.
In many cases, cleaning a process pipe or drain can be paralleled to cleaning tubes in an exchanger, and 10,000 psi water can be used. But in some cases, waterblasting is not possible. This was the case with a 1350' line that was newly installed for oxygen use.
Although the line had very few bends, the need to clean its ten down legs made it impossible to "pig" it clean. After confirming the line had room for expansion and all the pipe hangers could be loosened, the cleaning method of choice was Vapor Phasing. Recirculation would have been difficult because the pipe ran 1350' in one direction with no lines available to return a solution or vapor.
After fabricating a steam and chemical injection spool piece for one end and a cold water quench pipe for the other, Eagle Services put 300 pound steam to the line. Once the entire line was hot, the crew followed Eagle Services' procedure for new oxygen service line cleaning.
The first stage was to degrease with caustic, soda ash, SMS, TSP and surfactant in the appropriate ratios. Stage two included an ammoniated citric at the proper pH and concentration. The final stage called for adjusting the pH with ammonia and then adding the proper amount of sodium nitrate to passivate.
During each stage, the main line and down legs were cycled. All quench effluent was neutralized and disposed safely on site; and the ends of the pipe were capped until the line was put into service.