Fin Fan Cleaning Improves Heat Transfer

Air pressure of tubes tested and repaired

Summary

Tube Tech International used its all-round expertise to satisfactorily solve several problems with the fin fan air blast coolers at the Engineering Steels Division of Corus. Tube Tech took on the total management of the project at the Thrybergh Bar Mill near Rotherham in Yorkshire, covering all aspects of the cleaning, inspection, pressure testing and tube plugging operations.

Challenge

• The problems were centred on the closed-circuit water cooling system for a reheat furnace in which the fin fan coolers were seriously underperforming.
• During the reheat process the billets of steel are taken through the furnace on walking beams.
• The walking beams are water cooled and the thermal load is 15MW.
• A main concern was that the small-bore tubes in the cooler had become clogged with dislodged corrosion products, resulting in reduced water flow and poor heat transfer.
• Also of concern was the number of leaking tubes and the uncertainty of how much working life remained in them.
• The previous cleaning practice had been to wash the external finned surfaces of the tubes.
• It was also imperative to keep the shutdown period of the cooling units as short as possible.

Solution

• Before tackling the concerns about available life left in the tubes Tube Tech technicians had first to clean them inside and out.
• Deposits on the internal faces were removed using the Tube Tech WysperFlex system with SafetyBoss which cleans without damaging the internal tube surfaces.
• The Tube Tech SafeJet system was used on external surfaces and this was followed by internal electromagnetic checks of the tube wall thickness.
• Each individual tube was then air pressure tested to locate tube leaks and bespoke mechanically-expanding plugs used to seal them.
• A major benefit was the short downtime.
• Although there were five phases to the project Tube Tech technicians took just three days to complete the job by working around the clock, achieving the desired improvement in heat transfer, some energy savings due to efficiency and improved production throughput.

Client Comment

An Independent heat transfer consultant of Lincoln-based Industrial Energy Surveys said: “As on earlier jobs of this type Tube Tech did a good job. Tube Tech has good methods and are resourceful. Tube Tech are dependable; they always achieve a satisfactory result within the short window of opportunity of a planned shutdown despite unexpected eventualities.”

A Corus, Thrybergh-based, Mechanical Engineer said: “The Tube Tech teams did an excellent job in the short time that was available to them. We asked them to carry out the work on a 24-hour basis as time was short and other work had to be carried out during the downtime. The work by Tube Tech has increased the heat transfer of the coolers which were blocked and there is now a reduced risk of plant failure, with the added benefit of energy savings.”

Tube Tech Comment

Scott Donson. Technical Sales Manager: “This contract was challenging but with detailed planning and the ability to access a variety of cleaning equipment we once again provided an excellent service to our client.”