13 DESCALING POWDER
Scale and rust remover, acidic powder
Description
Aquamarine Descaling Powder is a dry acid cleaner formulated to remove water and rust scale deposits.
Uses/Benefits
- Powder product - safe and easy handling and storage
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Fast and effective scale remover
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Inhibitors protect normal constructional metals
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Contains anti-foam agent
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Colour indicator shows solution strength
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Removal of water scale from boilers
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Descaling of diesel engine cooling systems
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Removal of water scale and rust from condensers, evaporators, calorifiers & heat exchangers.
Dosage/User Instructions
- For large systems or components the most effective descaling is accomplished by circulation.
- In the case of small components, the soak method in an immersion bath can be used.
- If the equipment to be cleaned is contaminated by oil, grease or sludge, then pre-cleaning with Aquamarine Aquawash is necessary. For heavy deposits of carbon residues use Aquamarine Tank Cleaner H.D.
- Aquamarine Descaling Powder should normally be mixed with fresh water to form a solution between 2.5 and 10%, depending on the extent of scaling. At this optimum strength, the solution will be a red colour. It will change colour to orange when 85% of the acid has been neutralised, and to colourless when all the acid has been neutralised. Whenever possible, the solution should be heated to 60oC.
- Calcium sulphates and heavy iron oxides may need stronger acid solutions. The strength of the acid can be sufficiently enhanced by adding 1 part sodium chloride (common salt) to 20 parts of Descaling Powder. If salt is not available an acceptable alternative is to dissolve
- Descaling Powder in sea water. After use of Descaling Powder, a neutralising solution of sodium carbonate in fresh water should be circulated for 2.4 hours or until an acceptable pH value is obtained around pH 7. This will neutralise any remaining acidity and passivate steel surfaces.
Descaling Powder should not be used on aluminium, zinc, tin or galvanised surfaces for which a special grade cleaner should be used.
Descaling of boilers
Recirculating cleaning: The most efficient cleaning method is to use a recirculation system, heating the cleaning solution to 60oC throughout the operation. Live steam heating will cause an increase in solution level for which allowance must be made.
1. Open the superheater and boiler drum vents to prevent gas build-up during the cleaning process.
2. Connect a non-collapsible hose from the suction side of a portable pump to the water-drum blowdown flange.
3. Connect a steam supply hose to the water-wall header or to the water-drum blow down flange opposite the pump suction connection.
4. Connect a mixing tank to the circulation suction line between the pump and water-drum blowdown flange, or arrange to gravity feed the solution directly into the boiler.
5. Connect the delivery side of the pump to the auxiliary feed line so that the circulating solution will flow into the boiler through the economiser to the steam drum, then via the boiler tubes to the water-drum and out through the blowdown flange connection.
6. Arrange to check the circulating acid solution for colour and temperature during the cleaning process.
7. When all connections are secure, half fill the boiler with fresh water. Slowly add the calculated amount of Descaling Powder to the mixing tank to make up the 5% - 10% solution in water heated to 60oC.
8. As the cleaner crystals dissolve, start the circulation pump and take a sample of the solution for later colour comparison. The circulation flow rate should be maintained at 30cm/second for between 4 and 8 hours.
9. Apply head (steam) to maintain the cleaning solution at 60oC.
10. If needed, add fresh water until the solution level in the steam drum is 10cm over the tube sheet. Do not cover the tube sheet by more than this amount initially if live steam heating is used, as this may raise the water level considerably during the cleaning process. The solution level should be maintained at ¾ of the upper gauge glass throughout the operation.
11.Check the solution colour periodically against the sample taken when cleaning began. Colour changes towards orange and yellow indicate neutralisation of the solution. In this case add sufficient Descaling Powder to restore the solution to its original colour. Such additions should not be carried out more than twice during the cleaning operation.
12. If, after two cleaner additions, the solution still becomes completely neutralised, it should be drained off. The operation should then be started with fresh solution. This will usually only occur when very severe deposits are present.
13. When the solution retains its colour for 1 hour, the cleaning operation may be considered complete and the solution drained off.
14. Thoroughly flush the boiler with clean, fresh water. An alkaline neutraliser should be added to the final rinse to remove any remaining acidity and passivate steel surfaces. For this purpose use a solution of sodium carbonate and circulate for 2 to 4 hours or until an acceptable pH value is obtained (minimum pH=7).
15. Remove the circulation system and heating equipment. Refill the boiler with distilled water, test and add the appropriate water treatment chemicals before returning the boiler to service.
Descaling of diesel engine cooling system, condensers, evaporators, calorifiers, heat exchangers
Recirculation cleaning: Generally the most efficient method is to use a recirculation system, using 5% - 10% solution heated to 60oC for the duration of the cleaning operation. The process will need sufficient cleaning solution to fill the water side of the heat exchanger plus up to 50 litres for the circulation system.1.Isolate the heat exchanger from the water circuit and drain.
2.Fit suitable valves in place for the heat exchanger cleaning plugs and drain off any remaining water. If cleaning plugs are not fitted, use the water inlet and outlet connections.
3.Connect the discharge side of an acid proof portable pump to the lower heat exchanger connection and the suction side of the pump to the bottom outlet of a 200 litre open top drum.
4.Complete the circuit by connecting the upper heat exchanger connection to the top of the drum.
5.Arrange an immersion heater in the drum with sufficient capacity to maintain the solution at 60oC throughout the operation.
6.When the connections are secure add the appropriate amount of fresh water to the drum and slowly add the Descaling Powder. When dissolved, start the circulation pump and heating system.
7.Take a sample of the solution for colour comparison later.
8.Maintain the heat and circulation for between 4 and 6 hours, checking the solution colour and temperature regularly. If the solution changes from red-brown to orange or yellow, indicating acid neutralisation, add sufficient Descaling Powder to the solution to return it to its original colour (usually 25g per litre of solution). This solution enhancement should not be carried out more than twice. If after two additions, the acid is still neutralised, the solution should be drained off and the process started again with a fresh solution. This will usually only be necessary when dealing with very severe deposits.
9.When the cleaning solution retains its red colour for 1 hour, the cleaning operation may be considered complete and the solution drained off.
10.Thoroughly flush the heat exchanger with fresh water. Add an alkaline neutralising agent to the final rinse to remove any remaining acidity and passivate steel surfaces. For this purpose use a solution of sodium carbonate and circulate until an acceptable pH value is obtained (minimum pH = 7).
11.After rinsing, remove the circulation system, remove the temporary valves, replace the cleaning plugs and reconnect the heat exchanger to the normal water supply.
1.Isolate the heat exchanger from the water circuit and drain.
2.Remove both cleaning plugs. If cleaning plugs are not fitted, use water inlet and outlet connections. Replace the lowest plug with a valve to which a steam hose should be connected, the upper valve must be vented to atmosphere.
3.Using fresh water at 60oC, mix sufficient cleaner at 5% solution to fill the heat exchanger three quarters full. Take a sample for later colour comparison, then carefully pour the solution into the heat exchanger through the top valve.
4.Use live steam to maintain solution temperature at 60oC. Check the solution regularly by comparing with the original taken before cleaning started.
5.If the cleaner solution turns orange or yellow, add more Descaling Powder at the rate of 25g for every litre of solution to restore the solution to its original colour. This solution enhancement should not be carried out more than twice. If after two additions, the acid is still neutralised, the solution should be drained off and the process started again with fresh solution. This will only be necessary when dealing with very severe deposits.
6.When the solution retains its red colour for at least one hour, the cleaning process may be considered complete and the solution drained off.
7.The heat exchanger must now be thoroughly flushed with fresh water. If possible, add an alkaline neutralising agent to the final rinse to remove any remaining acidity and passivate steel surfaces. For this purpose, use a solution of sodium carbonate. Connect the hose delivering the rinsing solution to the upper heat exchanger valve and remove the steam supply from the lower valve. The water discharging from the lower valve may be drained into the bilges.
8.After rinsing, remove the temporary valves, replace the cleaning plugs and reconnect the heat exchanger to the normal water supply.
Dosage Rates
Aquamarine Descaling Powder should be used at a maximum of 10% solution. Stronger acid solution may be prepared by using 10% solution containing a mixture of 20 parts Descaling Powder and 1 part sodium chloride (common salt).