54 



AGRICULTURE HANDBOOK 134, U.S. DEFT. OF AGRICULTURE 



should be washed off immediately with large 

 quantities of water. Also, it should be removed 

 from clothing and equipment by rinsing repeat- 

 edly with large quantities of water. Bulk sup- 

 plies should be stored in a tight container in a 

 dry place. 



Despite its strong acid characteristics, sul- 

 famic acid has only a slight corrosive action on 

 most metals except zinc plating, especially if 

 contact is for a short period. For example, on 

 tin (the metal coating of most evaporators), 

 hydrochloric acid is almost 25 times more corro- 

 sive than sulfamic acid and sulfuric acid is 

 approximately 80 times more corrosive. 



Gluconic acid, another chemical cleaner, is 

 recommended for cleaning galvanized-iron 

 equipment because it has much less corrosive 

 action on the zinc coating. However, use of 

 gluconic acid need not be limited to cleaning 

 galvanized equipment; it is effective on most 

 metals, even though it has a slower cleaning 

 action than sulfamic acid. It is usually sold as a 

 50-percent water solution. 



Both sulfamic acid and gluconic acid can be 

 obtained from suppliers of maple sirup equip- 

 ment. 



Use these amounts of acid: 



Sulfamic Acid. — For a thin scale, use V4 

 pound (V2 cup) per gallon of water. (This is a 3- 

 percent solution.) For a heavy deposit, use V2 

 pound (1 cup) per gallon of water. (This is a 6- 

 percent solution.) 



Gluconic Acid. — For all deposits, use 1 gallon 

 of 50-percent stock solution (obtained from your 

 supplier) for each 4 gallons of water. (This is a 

 10-percent solution.) 



To avoid damaging the tinned surface of the 

 evaporator, do not use a stronger solution than 

 recommended; and do not leave the solution in 

 the evaporator longer than is required to soften 

 the scale. 



Cleaning Procedure 



Use the same methods to clean the flue (sap) 

 pans and the sirup (finishing) pan. 



You will need a good supply of piped water, so 

 that you can use a hose to rinse the pans. If 

 water is not available at the evaporator house, 

 take the evaporator pans to a source of piped 

 water. 



You should wear rubberized gloves to protect 

 your hands from the acid solution. 



The best maintenance practice is to remove 

 the sugar-sand scale between each run. The 

 following procedure should keep the evaporator 

 clean and bright: With a cloth, swab the pans 

 with the acid-cleaning solution; allow it to re- 

 main a few minutes; then thoroughly rinse the 

 pans with water, to be sure the acid is com- 

 pletely removed. 



If a layer of scale has accumulated on the 

 evaporator, use the following procedure: 



(1) Remove all loose scale and dirt from the 

 pan with a broom or brush. Then rinse the pan 

 with a good stream of water from a hose. 



(2) Plug the outlets of the pan. If the outlets 

 have threaded fittings, use metal screw plugs; 

 othei-wise, use wood, cork, or rubber stoppers. 



(3) Fill the pan with water to the level to be 

 descaled. Measure the water as you put it in 

 the pan, and make a record of the number of 

 gallons for future use. Also, make a I'ecord of 

 the estimated volume of the pan. 



(4) Add the correct amount of acid to the 

 water in the pan. Stir to help dissolve the acid. 



(5) Warm the solution in the pan to a temper- 

 ature of 140° to 160° F. This hastens the rate at 

 which it softens or dissolves the scale. After the 

 warm solution has been in the pan for a short 

 time (usually 15 to 20 minutes is enough), brush 

 the sides and bottom of the evaporator with a 

 fiber brush to speed up removal of the depos- 

 ited sand. 



(6) When the evaporator is clean, drain the 

 acid from the pan. Turn the pan on its side and 

 flush it out with a stream of water. Repeat the 

 water rinse five or six times, and allow the pan 

 to drain between each flushing. Thorough rins- 

 ing is necessary to insure complete removal of 

 the acid and its salts from the pan. 



To remove a thin layer of scale with sulfamic 

 acid requires from 30 to 35 minutes; to remove 

 a thick layer requires from 60 to 90 minutes. 

 With gluconic acid, about twice as much time is 

 required. The acid solution can be stored and 

 reused a number of times. Do not store it in 

 iron or galvanized containers; glass or earthen- 

 ware containers are best. 



To economize on the amount of acid, use a 

 smaller quantity of solution and tilt the pan 



