Page 175 - Machinery Component Maintenance

Process Machinery Piping 157

Preliminary Work

1. Install an acid-resistant pump connected to a circulating tank.
2. Provide 1 1/2 in. (or greater) acid resistant hoses for the connections
(prepare suitable assembly sketch).
3. For ensuring the filling of the system, flow must go upward and
vents must be installed.
4. Provide method for heating the solutions (e.g., a steam coil).

Pretreatment
Pretreatment is required only when traces of grease are present.

1. Fill the system with water at 90°C (194°F).
2. Add 2 percent sodium hydroxide and 0.5 percent sodium metasili-
cate (or sodium orthosilicate if cheaper). If these compounds are
not available and only a small amount of grease is present 2 percent
of NaOH and 3 percent of Na2C03 may be used.
3. Circulate for 20-30 minutes at 90°C (194°F).
4. Dump the solution and wash with water until pH = 7.

Acid Treatment
1. Fill the system with water at 50°C (122°F).
2. Add 4% of Polinon 6A@ and circulate to ensure its complete distri-
bution.
3. Add hydrochloric acid to reach the concentration of 7 % .
4. Circulate intermittently for about 45 minutes or more until the pick-
ling has been accomplished.

Notes:

1. In order to avoid corrosion:
(a) Keep the flow rate lower than 1 m/sec.
(b) Take samples of the solution and check for the Fe+++ content: if
[,+++I > 0.4%, dump solution.

2. In order to determine when the system has been adequately pickled,
put a piece of oxidized steel in the circulation tank and inspect it
frequently.