Project Description

FFS on the inner coil of a Biomass Direct Fired Heater

Fitness for Service (FFS) is one of the many services that Assistu offers. Performing an FFS essentially is used to identify the cause of the damage, determine the condition of the equipment, and provide mitigation and monitoring solutions to meet the remaining life requirements of the client. This assessment can be applied to a variety of industries. In this case, Assistu was able to perform an FFS on the inner coil of a Biomass Direct Fired Heater for the Lumber Industry. The heater heats the oil used for the sawmill while wood shavings were provided for fuel. It turned out that the inner coil had flame impingement, which means the flame was directly in contact with the inner coil tubing’s outer surface. This caused an increase in creep damage (severe degradation of the material which makes it more susceptible to cracking and weakens the material). The outer coil had no history of damage and was original to the heater. The client wanted to postpone the replacement of the coil, so Assistu worked with them to find a solution to ensure operations can continue safely until the next shutdown. It was recommended that the cracks were welded and the weld caps were blend ground to remove stress risers. Most of the cracks originated from past repairs where the cracks were initiated at the toe of the welds. Additionally, refractory was installed over the first few coils, where most of the damaged areas were located, so flame impingement is prevented in the future. Refractory is essentially used to insulate the coil from the flame. Assistu provided a detailed repair procedure which included modifications to their integrity program to ensure the safe operation of the equipment. Although the efficiency of the heater is reduced, the trade-off with this approach is a quicker and cheaper turnaround of repairs. The FFS reduced the downtime of the equipment by several weeks and allowed operations some time to source or fabricate the coil. This resulted in the heater operating safely until the coil is replaced.