Apparatus and method for withdrawing a broken tube expander tool trapped in a bank tube during tubeexpansion processof Bi- drum boiler

Abstract

An apparatus developed for withdrawing a broken tube expander trapped in a bank tube during the tube to tube sheet expansionprocess of a bi-drum boiler. The roller expander contains rolls set at an angle to the body of the expander, tapered mandrel to push out the rollers when rotating clockwise. As the mandrel rotates inward, the rolls develop the internal force, which expands the tube. There are chances that the mandrel may get sheared off during the expansion process due to higher interference, material weakness, etc.,Thickness of the tube considered for testing the developed apparatus is 4, 4.5, and 5 mm, and apparent wall reduction has taken as 6, 8, 10, and 12%. The amount of force required to drive out the body of the expander mandrel varies from 14.42 kN to 22.50 kN when it is pulled out axially. The apparatus is designed and tested to take up an axial load of 45 kN. The developed apparatus torque istested up to 450 N.m, that isthemaximum torque developed by HED-6 Hydraulic drive. Damage to the tube, tube sheet, and expander body can be avoided while removing the broken tool by using the developed apparatus.