Tank (Bitumen Storage) Cleaned with Combination Jetting Unit
Coke and carbonized coke removed from tank
One of the world’s oldest and largest oil companies called Tube Tech to solve a tough cleaning problem in a bitumen storage tank – removing an accumulated overhead layer of carbonised bitumen. This was posing a hazard to routine cleaning of the tank. This global oil company’s refinery has 20 bitumen loading tanks of similar sizes, holding different grades of bitumen. The tanks are around 10 metres tall, 6 metres in diameter and hold 150-200 tons of bitumen, which is heated to between 190-220°C.
- Due to the fact that bitumen is stored at different temperatures, some of the tanks suffer from coke build-up more than others.
- Coke generally accumulates on the heating coils, of which there may be 1-3 – depending on the grade of bitumen – at the bottom of the tank.
- A coke layer had formed on top of the product, rising and falling with the tank level.
- This resulted in the build-up of a thick, crusty, carbonised layer – up to 1 metre wide and 1.5 metres deep – around the top of the tank, just below the roof level.
- The coking problem was obstructing the tank level sensor, which normally floats on top of the bitumen.
- The standard cleaning procedure had been for operators to enter the tank and cut the coke away with pneumatic chisels. The discovery of the overhead layer of coke meant it was impossible for work to be carried out in the tank safely. The coke could be dislodged by vibration from the drills.
- The client had tried opening more slots in the roof to improve access, with the aim of cutting through the coke, but it remained well adhered to the tank shell.
- Attempts were also made to lever the coke off in wedges, but they were unsuccessful.
- The problem could be solved using a combination jetting unit which can convert from 1000 bar to 3000 bar within 15 minutes and a remote manipulator to direct the cleaning head to all areas inside the tank.
- Based upon the previous years’ experience, Tube Tech returned to tackle the same problem in a second tank and advised the client to carry out some minor tank roof modifications beforehand – which made the job much easier.
The customer stated: “Tube Tech was able to reach the coke deposits safely via the top of the tank, using safety apparatus and some very impressive Kevlar protective ‘turtle suits’, which protected them from any stray water jets during the cleaning procedure. The operators cut the coke away from the top in large chunks that then fell to the bottom of the tank for later clean-up. By successfully completing the work within the promised two days, Tube Tech ensured we kept the tank clean on schedule and made it possible for the regular cleaning team to work inside safely.”