A German refinery in need of some serious cleaning, asked Tube Tech in Essex, U.K., how it could reach deep into the rows of convection tubes within the fired heater. The cleaning project included removal of fused refractory that had cemented itself between the tubes over many years.

Traditional water-jetting and chemical service contractors were not getting the job done. Besides the water-jetting, the refinery had previously cleaned the heaters with chemicals, abrasive shot-blasting and dry ice, all with limited success mainly because the blast methods cleaned only what the operator could see. Therefore, buildup deep inside and between the furnace rows remained, and the furnaces had not been cleaned properly for more than two decades.

The refinery’s request led Tube Tech to develop a remote-controlled furnace robot. The contract was to clean three levels of each of the two fired heaters containing six convection banks times 49.2' long (15 m long), all within 48 hours. Because the refinery was changing the heaters from oil to gas, the tubes had to be free from hydrocarbon fouling to ensure maximum heat transfer, reduced fuel consumption and longer asset life. In addition, there could be no refractory damage, and sulphuric acid vapor had to be contained.

According to Tube Tech, the big advantage of the furnace robot is that it can remove extremely hard deposits deep within every tube row whether the design is square or triangular pitch, providing 360° tube-surface contact with the heater shut down and offline.

“What I can say is the stack temperatures of the furnaces dropped by 122°F [50°C] in HVU2 and 176°F [80°C] in CD2, which is a considerable increase in furnace/ energy efficiency,” Tube Tech says the client reported. Tube Tech says the client also said: “We are talking about several megawatt of energy savings. Various out-of-the-box cleaning techniques and ideas from Tube Tech could certainly improve our performance - heat exchangers as well as furnaces.”

According to Mike Watson, Tube Tech’s managing director, the project “was challenging because our three R and D engineers were given only three weeks notice to build three-times multi-functional robots.” Watson notes that the technology “overcomes all obstacles of limited access, allowing robotic cleaning to be done via small and awkward access doors.”

For more information, go to www.tubetech.com.