Rapid Reaction To Clean ‘U’ Tube Gas Cooler Offshore
Immediate mobilisation saves offshore platform £1000’s
Summary:
The ‘hairpin’ tube Gas Cooler on a North Sea oil platform was blocked by a break down of ferrules (material inserts within the tube ends) in the first pass of the heat exchanger. The contract was time critical as the platform was losing 8000 barrels a day.
Timeline:
- Mon 22nd June:
Onshore Operations Co-ordinator contacts Tube Tech. Tube Tech set up equipment in house, test and calibrate in readiness.
- Wed 24 June:
Clients inspector visits Tube Tech workshops, equipment packed and shipped over night to Peterhead.
- Thurs 25 June:
Tube Tech team arrive in Aberdeen.
- Fri 26 June:
Tube Tech team arrive offshore.
- Sat 27 June:
Equipment unloaded from ship at lunch-time and work begins.
- Sun 28 June:
Tube Tech work through the night.
- Mon 29 June:
10:30, 20-hours later work completed.
Challenge
- Blocked 14.83-mm i/d hairpin tubes within a shell and tube exchanger. With high pressure gas on the tube side and sea water on the shell, located on a North Sea offshore platform.
- Modifications to the tube bundle included additional ferrules to the inlet quadrant to help reduce tube end erosion and erosion around the tube expansions.
- Increased back pressure on the tube side, believed to be caused by a break down of the ferrules had blocked the tubes.
- Degraded insert particles were being caught in 5 micron filters downstream.
- Platform production capacity was severely effected by these blockages.
Solution
- Once the header was removed Tube Tech inspected the tubes. Confirmed 937mm long ferrules had clogged the tube bores. Broken ferrule sections had lodged in the ‘U’ bends of the heat exchanger. Others had folded back on themselves but remained adhered.
- Bottom half tubes were severely effected with 94 tubes completely blocked, effectively limiting the unit to 5% flow.
- Tube Tech used their SafeFlex™ system to safely drill the straight and then the tubes were the DarTTed around all hairpin bends to remove any remaining debris.
Tube Tech comment
“We originally thought the contract would take 48 hours and were pleased that the contract was completed in less than 24 hours. Tube Tech’s ability to mobilise so quickly was a huge bonus to the client.”
Clients can be contacted via Tube Tech for references.
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