The Challenge

• Tube Fouling included ferrous oxide scale, PCA (Polycyclic aromatics) and ammonium salts.
• Fouling characteristics were hard hydrocarbons including gum and solid coke blockages at various levels.
• Client estimated 40% of the tubes were blocked.
• Cleaning was completed within a very short time due to shut down restrictions.
• Access only via a small 14-inch top nozzle as the top header could not be removed.

The Solution

• Three technologies were applied to cater for narrow access, varying deposit characteristics and the need to drill at 30° from the 14 inch nozzle to the outer tubes.
• A bespoke solution was developed to access outer tubes from the nozzle but still maintain pressure and torque whilst moving the fouling safely without tube damage.
• A low wattage, electronic SafetyBoss was developed to eliminate the risk of cleaning hands and lances exiting the tube unexpectedly.
• Severe coke blockages were removed using a rigid drilling system, whereas softer gum like deposits used a more flexible drilling method.
• In house trials using standard off the shelf cleaning technology was found to be slow due to the gummy nature of the deposit inside a 20m x 12mm tube. The unit was stripped down, rebuilt with more power. At one stage 3 drilling units were operating simultaneously.
• A final pass was used to polish the tubes with the remaining time.