The tube assembly device of the present invention maintains spacing for proper heat transfer and avoids tubing wall removal should weld failure occur, thereby decreasing leakage of boiler tubes, shut down time and unscheduled down time for inspections and repairs. Productivity of the boilers is increased and maintenance costs are decreased. In the event of excess stress on the positioning assembly, the retainer assembly of the present invention allows for failure points to occur on the boiler tube position retainer assemblies rather than on the boiler tubes themselves.