A five day shut down had been planned at an oil refinery to accommodate traditional pressure jetting and chemical cleaning methods to clean four crude train heat exchangers. Tube Tech challenged this route using an alternative innovative method to overcome the main disadvantages: Difficult to clean with lengthy downtime leading to expensive lost production.
The company was able to clean each bundle in a few hours without chemicals or high pressure water jetting, while the other three exchangers were kept running to maintain continuity of production, effectively 'flat lining' the production output. The cleaning procedure delivered a substantial Kj/C-hr improvement on just one bundle compared to all four bundles previously cleaned with either of the traditional procedures.
Cleaning technology
There has been little change over the decades in the methods and equipment used to clean and de-scale heat exchangers and pipelines. The low-tech approach of high pressure water jetting has kept it as a low skilled job with largely unimpressive and variable results.
Despite being armed with demonstrable evidence of being able to achieve better results than traditional methods, the company has faced an up hill struggle to get its innovative techniques widely accepted. It has not been easy persuading potential clients to consider trialling new techniques designed to improve substantially on traditional water jetting methods.
There has even been outright skepticism that Tube Tech's claims can be substantiated. Persistence and determination were needed to change the industry mind set regarding the effectiveness of current cleaning methods. Long-term maintenance contracts can also act as a barrier to an investigation of the company's advances.
The historical reliance on low tech, low skill water jetting for pipe cleaning has meant that clients have accepted that this is the best that can be achieved. This meant that there was often no quantifiable data against which Tube Tech's improved results could be measured.
Setting out to devise a more scientific approach to the whole cleaning and de-scaling process,
The company has created more than 40 innovative techniques. This has led to several 'firsts' in heat exchanger and pipeline cleaning processes. These developments include:
o The ability to clean exchangers in-situ where previously they were pulled.
o The ability to clean and unblock hairpin bends.
o Speed cleaning difficult bundles in hours instead of days.
o Online cleaning of difficult heat exchangers.
The introduction of more sophisticated technology enables the cleaning and de-scaling to be carried out faster so there is considerably less downtime, and potential mechanical damage to equipment is eliminated. Less waste, dry processes and the elimination of chemicals provides a safer and more environmentally acceptable process.
The company has also taken traditional pigging methods and tailored them to achieve much better results. Operating in a tube and pipe environment from 2mm to upwards of 1m, equipment is modified to suit the consistency of deposit and pipe configuration. A wider variety of deposits can be removed by an innovative drift system loaded into large diameter pipes through a very small aperture which then expands to suit the diameter. It also has the ability to return back down the same line without creating an expensive loop system.
Aluminum tubes
The scale which builds up in aluminum furfural exchangers is notorious for being highly tenacious. The accepted wisdom has been that due to their delicate nature, aluminum hairpin heat exchangers can only be cleaned using 200bar (3625 psi) bar water pressure.
This low-pressure approach only removes 20% of blockages and scale with the additional problem that it tends to compact coke deposits on the U bends rather than remove them. Working with clients sample tubes, Tube Tech's research and development team devised a combined mechanical and water jet system which used 2500 bar ( 40,000psi) to remove coke deposits and improve overall cleanliness to 90%.
The three-stage process included a sensitive mechanical hairpin-cleaning device coupled with exceptionally low volumes of water. First, each tube was cleaned using the Softdrill(TM) lance made from 'intelligent' metals to prevent damage to the tube wall. These soften on entering the U-tube and stiffen on extraction, while an oscillating motion drills the blockage using a mixture of water and an occasional infusion of food grade media at 12 * the pressure and four times the speed of the conventional approach. Finally, a micro turbine rotating under controlled hydraulic pressure was guided through each tube.
Not only were the results substantially improved but also cleaning was carried out in-situ, reducing downtime by 200% and avoiding possible handling damage, the cost of cranage and bundle pulling equipment.
A U-bend first
The inability of traditional water jetting to remove hard coke and oily sludge in the U bends in heat exchangers in crude oil distillation complex has produced a 70% cleaning standard.
After analyzing the nature and composition of the deposit and its dimensions, the Tube Tech approach was used. The result was:
o 99% of contamination removed.
o Hairpins cleaned for the first time ever.
o Heat exchangers returned to virtually as new condition.
o Cleaning operation completed in three times faster than the standard pressure jetting times, down from six to two days.
o Greatly improved throughput.
In-situ cleaning
Solving problems related to specific equipment often enables the company to further improve on its initial performance. The cleaning process for an important tube bundle In a catalytic cracker was initially reduced from nine days to six but this first experience subsequently lowered the barriers further. A smaller sister unit was subsequently cleaning in three hours instead of three days.
For the first time the operation was carried out in-situ, using a new turbine method, incorporating a low-pressure water jetting system avoiding the cost and effort of removing 10t of exchanger gaskets, scaffolding or cranes. In-situ cleaning lengthens the life of the bundles, which deteriorate through damage caused when they are removed for cleaning.
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