The customer had an old heat exchanger that should have been used in a new production line. In the initial position of the preparation works the heat exchanger was partially heavily corroded after six years of decommissioning and greatly reduced in its mode of performance. A new acceptance by the TÜV and the authorization for a new use in a new operation for the customer would have been difficult. The customer's request to Kipp Environmental GmbH came just before the installation of the used heat exchanger. The inner tubes of the heavily corroded heat exchanger had to be cleaned and de-rusted before commissioning. The heat exchanger was about 90 t heavy with a total length of 21 m.
Such heat exchangers used for steam generation usually do not need to be cleaned. However, a long period of decommissioning without any measures taken o preserve it led to heavy corrosion also on the inner tube surfaces. Thus, an insulating layer was formed, which would greatly reduce the energy efficiency and lead to high additional energy costs.
The customer was looking for effective methods to remove corrosion from 1562 tubes having the dimensions of 60.3 x 3.2 mm. The difficulty here was the following: the 6 m long tubes with the inner diameter of 53.60 mm were formed by about a third of their length of the smooth tube, and by the remaining two thirds - as tubes with concaves. The opening between the concaves is only 21 mm. Normal cleaning using high-pressure water came for this heat exchanger out of the question, since the expensive isolation of the heat exchanger would have been irreparably damaged. The tubes were also only accessible by manholes of 450 mm located over narrow chambers (800 mm or 15000 mm deep). A use of lances for cleaning was not possible. Due to the partly smooth and partly designed as a tube with concaves, they therefore had to be grind from two sides when cleaning.
The heat exchanger was transported for treatment from a plant in France to the customer in Germany. The transportation of the 90 t heavy heat exchanger was carried out mostly by ship. Kipp Umwelttechnik GmbH was able to see the starting position already on the ship.
The grinding of the pipes with concaves had never been tried before. In a very short time mycon as a sister company of KIpp Umwelttechnik GmbH calculated and produced a special method of application of the TubeMaster system for cleaning or grinding the pipes with concaves. TubeMaster is a cleaning device for the non-abrasive inner pipe cleaning using dry ice, or granules. During the operation the nozzle of TubeMaster is hampered by the pipe to be cleaned out. In addition to cleaning, the surfaces may be polished, if necessary. Even the surface quality of new pipes can be significantly improved using this procedure.
In this case, the customer was guaranteed that the removal of metal caused by grinding of the inner tubes - especially of the concaves located frontally to the grinding direction - would be only max. 2/10 mm in order not to damage too heavily the concaves grounded to deep into the tube. The value was exactly determined by a previous beam experiments during company’s own operation. This value has been exactly observed by the Kipp Group during active grinding of pipes and after testing them.
The heat exchanger could be grind on time and accurately. The works were carried out to the complete satisfaction of the customer in accordance with the prescribed standards. The subsequent pressure test of the heat exchanger (37 bar) revealed no complaints. The heat exchanger is fully operational again and is available to the customers now with optimized transmission power in the new production line.
mycon GmbH, Jens Kipp
mycon GmbH, Jens Kipp