The pin-tube element must be blocked by welding circular plates, with the samediameter as the outer tube, at the inlet and outlet of the outer tube (see Figure I).The circular plates must be made of boiler plate and should be approx. 15 mm thick.The welding must be performed by skilled personnel with knowledge andqualifications to perform certified welding.Step A: Gain access to the damaged tube through the smoke outlet box, furnace,and/or manhole.Step B: Before repairing a damaged pin-tube element the inner and outer tubeshould be cleaned.Step C: Cut two holes in the outer tube prior to mounting the circular plates, asshown in Figure I.Step D: Fit and weld the circular plates at the inlet and outlet of the outer tube. Aftercompletion ofthe repair work clean the working area.Step E: Close all access doors and mount the manhole cover. Replace the gasket ifnecessary.Step F: Refill the boiler with feed water and check for leaks before starting up.Step G: Start the boiler and check for leaks when the boiler is pressurised.
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