Cleaning a Copper Heat Exchanger

Procedure for elimination of calcium carbonate and other scales when cleaning a copper heat exchanger

  1. To begin cleaning a copper heat exchanger, start by setting  up a 30 or 55 gal barrel ½ full of water, and a recirculation pump, to pump into the heat exchanger, and return back from the heat exchanger to the barrel. The input should be at the bottom; the output should be at the top.

  2. Add ½ quart or so of silicone based antifoam; then add 5 gal, or as directed (depends upon size of system), of RTA 9947 to the barrel.

  3. Start circulation to the heat exchanger with the pump.  At the same time select a control sample(s) of metals contacted by the cleaning solution and place it (them) in a container, then add a small amount of the actual cleaning solution.  Visually observe for any adverse action on the metals.  Refresh this test solution on a regular basis.

  4. Test the % acid content of the returning solution. It should not go higher than 3 to 5% for the initial injection period.  See below for test procedure.

  5. Test every 15 minutes. When the % acid decrease is less than ½% between tests, add more RTA 9947, always keeping below the 3% total acid concentration.

  6. Continue to add more RTA 9947 until the % acid no longer decreases for a ½ hour period from the previous test. After the acid no longer reduces, you have completed the cleaning of a copper  heat exchanger.

Disposal of the solution in the system and in the barrel

  1. Drain the system and discharge safely of the solution in the barrel.  Flush the system with water.

  2. Refill the barrel with water, add 1 qt to ½ gal of RTA 1130 (diluted 50%), or Caustic Soda 50%, and recirculate for 15 minutes.

  3. Make sure that the circulation water tests higher than 8.3 ph. (Add 1 drop of Taylor #638 reagent, or equivalent phenolphthalein indicator solution-test sample turns red if above 8.3 ph)

  4. Drain and rinse the system with water by pumping water through the heat exchanger.

Acid Test Procedure  (See step 4 at top above)

Add 1 ml of cleaning solution to a 25 ml test tube with approximately 20 or 30 ml of water.

Add 2 drops of total alkalinity indicator (Taylor # 645, or equivalent) reagent.  If the solution stays green, the cleaning solution contains relatively little acid.

If the solution turns red, add 5.0 N sodium hydroxide (NaOH), until the solution goes to green.  Multiply number of drops required by 0.75% per drop (or the factor required on your acid test, which depends on the drop size).

Note-Control at a maximum of about 3% acid in the cleaning solution.