S1901-4-1.pdf

August 18, 1992 (5/95)

NOAA Standard Specification S1901-4-1

PAINTING OF POTABLE WATER TANKS

Reference: (a) Steel Structures Painting Council SSPC-SP-10

(b) Attachment A - Acceptable Paint Systems For Potable Water Tanks

(c) Steel Structures Painting Council SSPC-PA-2

1. Open and gas free tanks "safe for men". Remove and wipe out remaining water in tanks.

2. Plug all leading to and from tanks with tapered or expandable plugs to preclude the contamination of the potable water system with grit or debris.

3. Isolate the tank areas by masking or blanking to prevent blasting materials/dust from entering other areas of the ship.

4. Provide and install air supply to exhaust fans and ducting to the tank area, sized to adequately supply air and remove any airborne dust from the isolated areas.

5. Abrasive blast all internal tank surfaces to a Near White Metal Blast as defined by Reference (a).

** CHECK POINT ** (Surface Condition)

6. Remove all abrasive materials from inside of the tanks and vacuum up all remaining dust/residue.

7. Preserve the potable water tanks utilizing one of the approved coating systems identified in reference (b).

** CHECK POINT ** (Dry Film Thickness)

7.1 Measure dry film thickness of each coat applied for the

coating system selected. Measurements to be in accordance with reference (c).

7.2 Drying time between coats of specified coating for potable water tanks shall be a minimum of 48 hours at a minimum temperature of 70°F, using heated air if necessary to maintain temperature. Ventilation shall be sufficient to ensure continuous flow of air through the tank with at least one complete air change every 4 hours. Mixing and stand-in times

(induction times) shall be in accordance with manufacturer's instructions.

Painting of Potable Water Tanks S1901-4-1

7.3 Cure potable water tank coatings for at least 7 days

prior to filling with water. Maintain a temperature of 70°F within the tanks. Ventilation shall ensure continuous flow of air with a minimum of one complete air change every 4 hours.

8. Rinse tanks twice with fresh water prior to chlorination to ensure cleanliness of tank.

** CHECKPOINT ** (Final Closure)

9. Inspect tank for cleanliness, coating integrity and removal of plugs. Install manhole covers with new gaskets manufactured of either cloth inserted rubber or synthetic rubber sheet.

10. Fill potable water tanks with clean fresh water, chlorinated to 100 ppm free Chlorine. After a minimum of 4 hours the Chlorine level of each tank shall be checked by a certified marine chemist.

Any tank with less than 50 ppm shall be brought back to 100 ppm and the process repeated until a reading of at least 50 ppm is attained after 4 hours. When satisfactory readings are obtained, empty and flush the tanks with fresh water.

** CHECKPOINT ** (Water Sample)

10.1 Sample potable water for odor after chlorination. There

shall be no detectable presence of odor when compared to potable water used for filling.

11. TESTS/REPORTS/INSPECTIONS

11.1 Records shall be maintained, and two copies provided to

the COTR at the completion of the work item, containing the following information:

(a) Surface preparation method including name of abrasive.

(b) Dry film thickness for each coat.

(c) Dry film thickness for total system.

(d) Elapsed time between coats.

(e) Ambient temperature and relative humidity taken at two hour intervals in area being coated.

(f) Name of paint, manufacturer, batch number and date of manufacture.

(g) Material Data Product Sheets for each proprietary coating used.

(h) Marine chemist's report.

11.2 Tank cleanliness shall be acceptable to COTR.

Painting of Potable Water Tanks S1901-4-1

(Include Attachment "A" Coating Systems for Potable Water Tanks Specification table (k:\*\specs\specs.xlw)

ATTACHMENT "A" (CONT.)

The isolated areas shall be less than two percent of the total area.

Mix and apply coatings in accordance with Mfr. instructions except for surface preparation and minimum dry film thickness specified above.

NOTE 1. The following requirements apply to MIL-P-24441 coatings:

a. MIL-P-24441 polyamide epoxy paints do not require thinning to application. If desired, the low temperature application properties can be improved by the addition of 10% of volume of one-to-one mixture of butyl alcohol and high flash naphtha or paint thinner TT-P-291. When sprayed without thinning at the recommended thickness, the paints have no tendency to sag.

Apply a thinned mist coat of one to two mils wet film thickness over existing paint.

b. When MIL-P-24441 polyamide epoxy paints are used at a work site having temperatures below 50°F, it is essential that the stand-in period be accomplished in a warm area (70°F) to ensure that the coating will cure.

c. Exterior side shell and underwater body painting at surface temperatures between 25°F and 35°F, is not recommended, but can be approved by the COTR provided the following conditions are met:

1.) Ambient temperature must be a minimum of 5°F above the dew point.

2.) Hull surfaces must be absolutely dry and free of any signs of frost and ice.

3.) Drying time will be increased by 4 hours for a total of 8 hours drying time per coat.

4.) No painting is allowed below surface temperature of 25°F.

5.) Paint shall be stored at 70°F for 24 hours before use.

d. Painting shall not be accomplished unless surface is dry and surface temperature is at least 5°F above the dew point.

Painting of Potable Water Tanks S1901-4-1

e. Approximate temperature of paint components in storage should be estimated in order to judge the amount of stand-in time to allow and the pot life that might be expected. The work site application temperature will greatly affect the time required for the paint to cure, and must be considered in estimating batch size, stand-in time, and cure time.

f. Epoxy primers applied in the vicinity of abrasive blasting must be sheltered from airborne contaminants. Abrasive particles trapped in wet paint films are a source of premature blistering and film failure.

g. Mix MIL-P-24441 coatings in accordance with the following:

(1) The MIL-P-24441 coatings mixing ratio is one-to-one by volume. The components of the various formulas are not interchangeable.

(2) Blend each component thoroughly prior to mixing the components. After mixing equal volumes of the two components, the mixture must be thoroughly stirred, and the stand-in times listed below must be observed.

(3) Stand-in time (induction time) is defined as the time immediately following the mixing of the components during which the critical reaction period of the components is initiated and is essential to the complete curing of the coating. During stand-in time the mixture must be thoroughly stirred at least once every 20 minutes to avoid hot spots caused by localized overheating from the chemical reaction.

Surface

(Temperature at Job Site) Stand-In Time Degrees Fahrenheit

35 to 50 2 hours at 70°F (paint temperature)

50 to 60 2 hours at job site temp.

60 to 70 1 - 1½ hours at job site temp.

70 and above ½ - 1 hour at job site temp.