In-Situ removal of scale from tube bores/internal tube walls

Summary

A Middle East LNG plant had trialed several types of High Pressure Water Jetting techniques using various International contractors. All methods were unsuccessful in fully removing a thin film of protective coating from inside condenser tubes. The condensers would have had to be replaced if a proper cleaning method was not found.. Tube Tech was given an extremely short plant shutdown window and provided an effective cleaning system which could be applied in the narrow time frame of a mini process stop.


Challenge

  • A tenacious film existing along the entire length of the tubes within a variety of condensers. The tubes had localised galvanic corrosion.
  • Cleaning had to be done in-situ as condensers could not be pulled.
  • Ultra High Pressure could not achieve a suitable level of cleanliness
  • Chemicals could potentially etch the tube surface during cleaning and reaction would be difficult to spot. Plus the waste/environmental impact was deemed too substantial.
  • Client required 100% of the tube surfaces to be cleaned to a high “polished” standard within a very short shutdown window.
Polishing tubes in Oman Polishing tubes in Oman Video probe inspection to confirm level of clean UHP standard not accepted Rotaflex standard  accepted IRIS standard clean Confirming zero wall loss after polish Morning cleaning information

Solution

  • Tube Tech conducted trials with a prototype system at their UK headquarters in the clients’ presence.
  • A tailor made system was designed and developed specifically for this critical path requirement.
  • A multiple flexsafe system was used to remove scale and finish tubes to a high standard.
  • As timings were so critical, Tube Tech ensured precise timing per tube.
  • Up to 8 tubes were polished simultaneously and no surface was left untouched
  • Bore scope inspection carried out to set the cleaning standard after first tubes cleaned.
  • Tube Tech achieved a 100% polished finish on all tubes.

Tube Tech comment

Martin Byford GM / Ops Director: “Shell Global Solutions challenged Tube Tech to develop bespoke equipment to create a tube finish never before achieved on an LNG plant.
So critical was the timing that each tube had to be cleaned within one second tolerance per tube. Planning was time consuming but essential. The time frame was achieved and our client was highly impressed with our level of professionalism plus our efficient and safe working practices. Another world first!

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