Why heat exchanger retubing is required?

Heat exchanger tubes are constantly expanding and contracting as they heat up and cool down during normal operations. Depending on the application, saltwater scale, calcium, Lyme and other contaminants can compound the problem, leading to even faster deterioration

This causes a reduction in the efficiency of the heat exchanger. To restore the efficiency of the heat exchanger, tubes need to be replaced with fresh tubes.

The process of replacing the tube is called retubing and it involves the following steps

• Tube to tube sheet weld removal
• Tube removal
• Tube sheet hole cleaning
• Tube insertion
• Tube expansion or rolling
• Tube to tube sheet welding
• Hydro test
  
  
• Tube to tube sheet weld removal
  Not in all but most in most heat exchangers tubes are welded with tube sheets to maintain leak-free joint. With help of a pipe bevelling machine or hand grinder, the weld is removed.
  
  
• Tube removal
  Even after the removal of welding, the tubes are strongly bonded with tube sheets due to rolled joints. Tube pulling machine is applied here to automatically and faster removal of tubes from the tube sheet.
  
  
• Tube sheet hole cleaning
  Once the tube is removed, tube sheet holes are cleaned with carbon steel / stainless steel/nylon/brass brush depending on the material of the tube sheet. The tube cleaning brush is held in the spindle of the tube drill machine and passed thru the tube sheet hole at high speed.
  
  
• Tube insertion
  For accurate insertion of tubes in both the tube sheet hole, tube guides are used. Tube guides are conical aluminum guides with brushes at the tail end. This brush end is inserted in the tube ID to give an accurate guide while the insertion of tubes.
  
  
• Tube expansion or rolling
  After insertion of the tubes in the tube sheet, both ends of the tube sheet are rolled/expanded to form a leak-free joint. To do this a tool called “tube expander” is used. To accurately achieve the expansion, a tube expansion machine with a torque controller is used. These torque controllers control the amount of torque applied to the tube expander thereby giving accurate and consistent tube expansion.
  
  
• Tube to tube sheet welding
  As per the design, a recommendation tube is required to be welded to the tube sheet to further ensure leak-free joint
  
  
• Hydro test
  A hydro test is done to check whether all the joints are leak-free and the heat exchanger can be put into operation