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Texas Tower Mechanical Drilling of Vertical VCFE Texas Tower Tubes

Coke and Gum Blockages Removed from Critical Exchanger in the Caribbean

A blocked VCFE / Texas Tower on a large refinery in the Dominican Republic needed tubes unblocking to increase production throughput. Using a bespoke three stage system, designed specifically for cleaning “Vertical Combined Feed and Effluent Exchangers” Tube Tech removed blockages containing solid Coke and hydrocarbons quickly and remotely helping the client to gain increased heat transfer proficient and improved production.

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.
Tube Tech Comment


Operations Director “We have now cleaned this particular VCFE / Texas Tower twice. The first occasion was more challenging as the site drawings did not accurately reflect the dimensions hence having to drill from the ground upwards on the last occasion. We believe Tube Tech’s is probably the world’s leading and most experienced contractor, in cleaning of VCFE’s. With such experience it allows us to pinpoint the exact techniques required to match unusual access limitations as well as the severest of tube and even shell side fouling. Great communication with the client who was very pleased with the service” As with all contracts, provided one receives accurate information then the right technology can be developed and applied.”

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