As with all engines, a ship's engine needs to be cooled. However, with both boats and ships there is an advantage. They can use the water they are floating or moving in to cool the engine provided there is the correct equipment to prevent water from seeping into the ship. The only drawback on this is the potential for leaks in the air to water system, which can cause a boat or ship to fill with water and sink, and corrosion caused by the salts in the water and the debris clogging the cooling system by pollutants, zebra muscles and other mollusks. Cleaning heat exchanger tubes on large ships can be a very difficult job that requires the right expertise and the right equipment.
Cleaning marine heat exchangers requires some of the most proficient expertise and labor. This is because it requires a lot of work to climb into tubes and use some very interesting cleaning equipment. This equipment includes things like high power water hoses, brushes, chemicals, abrasive balls, and scrapers (both metal and plastic). Before anything is done a proper initial inspection helps engineers and workers to decide on what will be necessary before proceeding.
Tubes of all Sizes and Metals
Heat exchangers come in all sizes because they are used in boats of all sizes, from small boats to large ships that the coast guards and military use. Therefore the tubes in them also range from very small (less than one inch) to very large, some often larger than men and up to 800 feet long. All of these must be inspected, both before and after the cleaning job. In addition to the sizes of the tubes that are included, the make-up of the metals involved and any decision to remove and recoat any of the tubes. All of these are taken into consideration when planning how to go about properly cleaning heat exchangers.
Traditional Methods vs. New Methods
In the past, cleaning large pipes and tubing was not always successful and refouling often occurred quickly because of incomplete debris removal. The traditional methods of hydro blasting water through tubes had its drawbacks, the water flowed in one direction and therefore streaking on the inside of large tubes occurred. In addition, some of the contaminants (chlorides, salts etc) were pushed into the sides of the walls as the huge amount of water was blasted through the tube. Thus, when any recoating was done, it did not last long and refouling was frequent.
There has been a new method created in which more pressure (10,000-40,000 psi) is used with a rotating head. With this method the tubes inner walls are cleansed of all debris and corrosive salts because the head moves in a circular manner eliminating all debris, thus preparing the tube's inner wall to be clean enough that recoating is successful and the wall is as good as new when finished.
In addition to this benefit, only water is used, no hazardous chemicals are employed and thus in addition to saving money, the US Navy in addition to other users of this method reduces pollution of the earth's waters. So, as more and more companies use this new technology, which is called "hydro-lasing", the more we all benefit. In addition, this method can be used with all metals ranging from brass to titanium without harming the metals involved.
Post Cleaning Inspection
Another necessary part of the cleaning, and if necessary, recoating, of these large tubes involved in heat exchange is a post cleaning inspection. This is necessary for confirmation that a good job was done by the cleaning company. It also provides both ship, and boat owners as well as the cleaning company an opportunity to search for any hidden leaks that might have been missed.
It might surprise some that this is done almost completely with robotic cameras of all sizes. There are tiny "mini-cameras" to inspect tubes from 1- 8 inches in diameter and up to 800 feet long. Other inspection services are manned underwater inspection of the outer areas of the unit. This provides total confirmation to all that a job well done has been completed and the ship is very safe and worthy of traveling in the sea.
Heat exchanger tube cleaning is an important job that provides ships with a properly functioning part of an engine, whether it be a small boat or ship. The equipment has undergone great changes in order to make the job both more effective and environmentally friendly.