AN 01-25CN-2

PARAGRAPH 6

knuckle can be gently pressed against the cemented surface and then pulled away clean without any cement sticking to it, the surface is ready for the next coat of cement or patch to be applied.   If the cemented surface is not tacky, it may sometimes be freshened by wiping with a clean cloth, damp with solvent, or by applying another coat of cement. If this fails, the patch should be scrapped, the cement on the tank should dry and be buffed off, and a new repair started.   4. A recommended procedure for rolling down the patch is as follows: stick one end of the patch down first. Then gradually roll down to the other end of the patch, moving the roller perpendicularly to the long dimension of the patch and perpendicularly to the direction of advance of the rolled down area. During each movement of the roller, part of the roller must overlap the previously rolled down area to avoid trapped air. Do not let any part of the patch touch until rolled down in the prescribed manner or trapped air will probably result.   Always do patching in a dry place. Dampness and moisture make good adhesion difficult or impossible.   After the patch has been applied, paint its edges and buffed area of the cell with four coats of synthetic cement.   5. Cut a second patch which will extend at least 2½ inches beyond the first and apply the second patch in the same manner as the first patch.   (d). INSIDE REPAIRS.   l. If the cell has sloshing compound, remove it by dissolving it with ethyl acetate or by buffing around the injury for a distance of 2½ inches in all directions from the edge of the injury. Then buff with clean emery cloth.   All inside repairs should be buffed heavily; that is, all gloss should be removed and the surface should be covered with closely spaced fine scratches.   2. Cut a piece of repair gum with a smoothly rounded outline large enough to extend 1½ inches in all directions from the edge of the injury. Edges should be skived by tilting the shears when cutting out the patch, so that an obtuse angle between the tank surface and the edge will be formed when the patch is in place.

Give the flat side of the patch a heavy buff. Buff the edges to paper thinness. The flat side of the patch goes against the cell wall, the tapered side away from it.   3. Apply four coats of cement to the buffed side of the patch and the buff ed area of the cell wall.   4. Apply the patch to the cell rolling down as specified for the outside patch.   5. If, after the repair has been made, there are any bubbles, blisters, trapped air, or evidence of looseness, the patch should be torn off and the repair started over.   6. If the repair is satisfactory, paint over the entire surface of the patch with four coats of specified cement.   7. If the cell was previously sloshed, paint the entire patched area with two coats of Fuller's sloshing compound.   (e) FITTINGS.   1. If the injury in the fitting is surrounded and supported by the liner, it may be repaired in the manner prescribed for general injuries.   2. If the fitting injury is in an unsupported wall of the fitting or in the junction of the fitting wall and liner, the liner should be returned to the manufacturer for repair or disposition.   (f) LOOSE LAPS -Loose lap scams may be repaired by using the prescribed procedure of buffing, washing, cementing, rolling down, and painting of the loose lap without the use of additional patches.   (g) LOOSE PATCHES. - Treat in the same manner as a loose lap unless it is obviously better to replace the patch with a new one.   (h) GENERAL-All repaired tanks must dry at least 100 hours after the last repair is completed before being filled with gasoline. The drying time may be cut to 24 hours if for the first eight hours the repair is kept from 43°C. (110° F.) to 49°C. (120°F.). Do not raise the temperature above 49°C. (120°F.).   Always wash cement out of the brush with solvent immediately after use. If it is allowed to remain on the brush, the cement soon becomes insoluble.

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