Application of parallel ladder technique for purging oil residual inside the copper pipe

In iron pipe industry, one of the most important problems in manufacturing processes is the great amount of oil residual in copper pipe. This problem can be affected the use of copper pipe further such as difficulty in pipe soldering, pipe rust and leakage. This study aims to demonstrate the use of parallel ladder technique, the simple process with low additional costs, to purge out liquid residual in the pipe after ironing. This technique can improve the efficiency of the manufacturing process as well as increase the quality of the product. Nitrogen was applied in this process with the step-increasing pressure of 0, 5, 10, and 15 Bar. This supplied pressure levels are a function of time which depend on the length of pipe. Nitrogen with specified pressure levels were controlled by 3 sets of control valves which were parallelly arranged. For efficiency test, two sizes of copper pipe which are commonly used for producing coil of air conditioner were used as a case study, Pipe A (diameter of 7.29 mm, thickness of 0.25 mm, length of 10 km) and Pipe B (diameter of 8 mm, thickness of 0.25 mm, length of 10 km). From experiments, the parallel ladder technique can eventually reduce the liquid residual inside the pipe. For Pipe A, the residual was reduced from 1.468 mg to 0.045 mg or 3.65 %. For Pipe B, the residual was reduced from 1.916 mg to 0.054 mg or 7.29%. The average oil residual purged out from Pipe A and Pipe B were 1.42 mg or 96.35%, and 1.86 mg or 92.71%, respectively. It can also be indicated that water and oil residual in the pipe were significantly less than the standard limitation (0.1 mg/m or 30%).