Alternators, converting a prime mover’s rotational kinetic energy into eletricity, are a vital element on board any ship or in any power plant. They contribute greatly to the overall performance of the plant and thus deserve proper application and maintenance and must receive immediate and logical remedial attention once irregularities are detected.
Scheduled routine inspections and maintenance will minimize alternator problems. The frequency of routine maintenance depends on the alternator type, application and ambient conditions. During operation, attention should be paid to vibrations, excessive heat and abnormal noise. All of these indicate possible equipment failure.
Excessive heat is a sign of poor cooling that maybe caused by the accumulation of dust or oil, or by an internal damage, that restricts the flow of air through the alternator. The primary damage caused by excess heat is that it accelerates the insulation’s aging rate and shortens its life time. An approximate rule of thumb is that insulation life is reduced to half its normal life for each 10° C (50° F) increase above its design temperature.
QuantiServ offers a proven in-situ cleaning process that uses only water and a specialized, water-soluble degreaser. The process works as follows:
- Not much equipment needs to be removed. The stators and rotors stay in place. Thus, there are no (re-)alignment issues. Only access panels and, in some cases, cooling fans will have to be removed.
- Insulation tests (megger tests) of the rotor, stator, excitor rotor and exciter stator are carried out before and after the cleaning process.
- A special water-based degreaser and demineralized hot water is used for cleaning.
- Once the cleaning has been completed, the alternator will be tightly covered and will be dried by a portable heating and drying system.
The work can easily be carried out during the voyage, or alternatively in the dry dock or plant. It takes around five days to complete one alternator, drying time included. We usually send one engineer, who carries out all the work by himself but who needs full-time assistant from one crew member during the first two days of work on each alternator. All the tools and consumables that we need for a cleaning assignment are stacked into one pallet size box, which we send on board prior to the start of the assignment.
QuantiServ discourages the cleaning of alternators by electro cleaner and by CO2 (dry ice) for the following reasons:
- Electro cleaner is very volatile. It evaporates quickly, so quickly in fact that it does not reach dirt and stains that are hidden and more deeply embedded between the windings
- Electro cleaners are either fluorocarbon or methyl choloform (1,1,1 Trichlorethane). These chemicals are hazardous and toxic and their use is rapidly becoming restricted, particularly in areas where personnel are working.
- They are flammable and pose a fire hazard.
CO2 (dry ice):
- Dry ice pellets are often not easily available
- There is a significant risk of damaging the insulation varnish by thermal shock, in particular if the worker is inexperienced
The QuantiServ cleaning process does not suffer from any of these disadvantages as it only involves water and a water-soluble degreaser.
Benefits of a clean alternator
The advantages of a professionally cleaned alternators are many:
- Optimized performance
- Extended life time due to lower thermal loading
- Reduced downtime, reduced costs
- No power de-rating due to high winding temperatures
The image gallery below shows direct comparisons of alternators before and after they have been cleaned in-situ by our specialists.