Page 176 - Machinery Component Maintenance

158 Machinery Component Maintenance and Repair

Neutralization

1. Add sodium hydroxide for neutralizing the acid, and water to avoid
a temperature rise.
2. Circulate for 15-30 minutes.
3. Dump the solution and wash with water until pH = 7.
Note:

The concentration must be calculated on the overall volume of the so-
lution.

Passivation
1. Fill the system with water at 40°C (104°F).
2. Add 0.5% of citric acid and circulate to ensure complete mixing.
3. Check the pH of the solution: if pH < 3.5, slowly add ammonia to
raise pH to 3.5.
4. Circulate for 15-20 minutes.
5. Slowly add ammonia to raise pH to 6 in 10 minutes.
6. Add 0.5 % sodium nitrite (or ammonium persulfate).
7. Circulate for 10 minutes.
8. Add ammonia to raise pH to 9.
9. Circulate for 45 minutes.
10. Stop the pump and hold the solution in the system for at least three
hours.
11. Dump the solution.

Cleaning of Large Compressor Piping: Method II

Cleaning of the piping may be done by commercial companies with
mobile cleaning equipment or by the following recommended cleaning
procedure. After hydrostatic tests have been made and the pipe sections
have been cleaned as thoroughly as possible on the inside, the piping
should be pickled by the following (or equivalent) procedure:
1. Remove all grease, dirt, oil, or paint by immersing in a hot, caus-
tic bath. The bath may be a solution of eight ounces of sodium
hydroxide to one gallon of water with the solution temperature
180-200°F. The time of immersion is at least thirty minutes, de-
pending on the condition of the material.
2. Remove pipe from caustic and immediately rinse with cold water.