BAE Systems

Unblocking of coiled heat exchanger saves on replacement

Excessive water scaling was the cause of a number of problems at the BAE Systems factory at Brough in East Yorkshire where the Hawk Trainer aircraft is manufactured. The key focus for the Tube Tech team was to tackle a blockage in critical equipment.

Problem:

Contamination of heavy suspended solids had completely blocked a 5-cm diameter carbon-steel heating coil - a very critical item of plant that supplies steam for their production processes.

The mixture of silicates and carbonates had baked within the steel coil and was resistant to the effects of chemical treatments formerly employed. The client had even considered replacing the blocked 100-metre coil.

Apart from being costly, this option would have resulted in several weeks of downtime, performance reduction and the need for alternative ways of heating.

Solution:

The Tube Tech survey of the problem rejected the traditional approach of removing the coil and cutting it to clear the blockage. Instead Tube Tech recommended its own bespoke methods. It is believed this was the first time that a coil so blocked was cleared by a triple cleaning process with the coil intact.

The work was subject to two detailed inspections, the first using sound impedance developed by Tube Tech to assess the location and length of the problem. The blockage was then approached from both ends using a rotary drill within a protective water jacket.

This Softdrill™ method loosened the blockage in tandem with ultrasound equipment which vibrated blockages too far down the coil for the flexible unit to reach. DarTT™ system was fired through the coil until a full bore was achieved and a final chemical flush removed any loose deposits.

Benefits:

The client saved on the high cost of replacement and the inconvenience of the cutting-and-cleaning method and still achieved a coil returned to its efficient full bore. Additional reasons against the cutting approach were haphazard welded patches with the potential for future leakage.

Tube Tech Managing Director Mike Watson said: “Coiled or serpentine tubes are often the most difficult to clean, due mainly to inaccessibility combined with tortuous routes and hard deposits. Our teams avoided cutting the coil. Blockages were cleared and scale extracted using technology specifically developed by Tube Tech. We had the added difficulty of access via a 90-degree flange in order to enter the twin-coiled tube.”

BAE Brough’s Facilities Team Leader said:
“I was pleased with the work done by Tube Tech which was effective in that we have the coil back in operation. We have a potential for more work on which I will be contacting Tube Tech very soon.”

Clients can be contacted via Tube Tech for references