How to Maintain Marine Heat Exchangers on Ships?
Marine plate heat exchangers serve a vital role in eliminating heat produced by running ship machinery to maintain the equipment's proper operation. It is also important to improve the heat exchanging ability, which decreases after a given period of operation.
The cooling medium used in the heat exchanger is determined by the medium utilised as well as other considerations.
Sea water, along with fresh water, air, and oil, is frequently used as a significant cooling source in marine plate heat exchangers. However, corrosion and scale deposits are frequent in heat exchangers due to the presence of dissolved salts in sea water. Maintenance of maritime marine plate heat exchangers is thus required at regular intervals to prevent heat transfer decrease or device failure.
The technique of maintenance employed varies on the kind of heat exchanger and the type of deposits, but the overall goal of any heat exchanger maintenance operation remains the same - cleaning of heat transfer surfaces to prevent any sort of blockage in the flow process.
The major cause of heat exchanger surface fouling is a rise in the temperature differential between the two fluids as well as a change in pressure. The sea water side of the plate heat exchangers suppliers, on the other hand, suffers the most as a result of corrosion and scale deposits.
Methods of marine heat exchanger maintenance
Prior to maintenance, it is critical to isolate the heat exchanger by turning off the medium and media line valves and draining the leftover liquid via the drain cock. To guarantee that everything is drained from the heat exchanger, the Vent must be opened.
If the deposits on the heat exchanger are not too hard, a wire brush can be used to remove them.
If the deposits are very tenacious, chemical cleaning should be performed, which entails immersing the part in a chemical solution.
Depending on the kind of heat exchanger, the manufacturer may supply cleaning equipment. Cleaning shell and tube type marine plate heat exchangers, for example, requires specialised equipment.
After cleaning, rinse the heat exchanger with fresh water to eliminate any leftover chemical or debris from the surface.
Anodes are installed on the lid of a sea water cooled heat exchanger to avoid galvanic corrosion. Anodes must be examined and, if necessary, replaced.
Replace the lid gasket if it is damaged during heat exchanger opening.
Fouling can also occur on the outside of the tubes of oil coolers and heaters. To remove this, chemical flushing might be employed.
The stack of new and refurbished plate heat exchanger is removed to reveal the surface. The plate surface is next cleaned with a brush or according to the manufacturer's instructions. (It is best to avoid using sharp instruments.) Cleaning should be done in such a way that the plate seals are not damaged. However, if the seal has to be replaced, it must be done before reinstalling the plates.
Tightening the plates together requires careful attention to the equal tightening of all the exchanger studs and bolts, or else a leak may develop.
Excessive corrosion of the heat exchanger surface can potentially cause perforation, resulting in the mixing of two liquids. Minor leak identification is difficult, especially when header tanks are automatically toped or no adequate manual record is kept. Major leaks, on the other hand, can be quickly identified as a consequence of a rapid loss of lubricating oil or jacket water. Low-level alarms can also help identify large leaks.
Another method for preventing mixing of two liquids due to perforation is to keep the sea water at a lower pressure than the jacket water or any other liquid utilised. This reduces the possibility of seawater invading other media.
How are leaks detected?
Shell and tube type heat exchangers
Leaks in a shell and tube heat exchanger can be found using the following procedure:
Draining the sea water and isolating the plate heat exchangers exporter from the system
Taking off the end caps or headers to see the tubes or plates
If the surface is clean and dry, the liquid flow is inspected from the tube ends and via the perforations. However, it is difficult to keep huge coolers extremely dry in order to see any perforation. In such instances, a special fluorescent dye is applied to the cooler's shell side. When an ultraviolet light is shone on the tube, the dye glows, indicating the tube leaks.
Plate Type Heat Exchangers
Similarly, eye inspection or fluorescent dye penetration are employed to detect any flaws in plate type heat exchangers. (On one side, dye penetration is employed, followed by UV radiation on the other.)
Air coolers
Leaks in air coolers can be problematic because they allow sea water to enter the engine cylinder. This might result in the production of scales on the spindle of air inlet valves.
In such circumstances, the location of the leaks can be determined by allowing low air pressure on the air side and monitoring for air bubbles on the flooded sea water side. For best results, use soapy water for seawater flooding.
Aside from the procedures listed above, there are various ways to carry out maritime heat exchanger maintenance. These, however, are the most widely utilised.
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