Figure 9-21.—Outside ladder installed.

The left lap seam of the last plate slips under the right lap seam of the first plate. The right lap seam of the last plate is placed over the bolts in the left lap seam of the next-to-last plate installed. Make the necessary adjustments in the deck if the last plate fails to fit properly. Remove the nuts temporarily installed on all of the bolts in the plate lap seams. Install a rubber gasket, a steel recessed washer, and a nut on all of the bolts except on the bolts in the top chime of the staves. Install any missing nuts on the chime bolts. Make sure that the rounded head of the nut is against the plate and washers and that the cupped side of the washer is facedown covering the rubber gasket. Tighten the bolts. Remove the scaffold. Install the gaskets, the washers, and the nuts to all of the bolts in the vertical seams. Return the brackets and the posts to the tank erection tool set. MANHOLE COVER— If this tank is used for water storage, omit the emergency vent valve (fig. 9-21). Install the manhole cover with the blind flange hatch set after installation of the manhole air intake. Install a 30 bolt hole gasket on the top flange of the dome. Insert 1/2- by 1 l/2-inch bolts through the flange and gasket, in that order. The gasket will hold the bolts in place. Install a 30 bolt hole manhole cover (fig. 9-21, #1) over the bolts. Install the gasket, the washer, and the nut on all of the bolts. Install the washer and the nut as above. Tighten the bolts. Emergency Vent Valve The emergency vent valve consists of a one-piece, flanged, round, cast steel body, fitted with lugs for a hinged vent. The vent is a one-piece, round, cast steel body, fitted with a lifting handle and hinge lugs. The vent comes attached to the flanged body hinges and seals the deck opening. Place the manhole cover gasket over the bolt holes at the opening in the cover (fig. 9-21, #l). Insert l/2- by 1 1/2-inch bolts through two bolt hole channels. Work through the l0-inch hole and insert the bolts through the cover and the gasket. Install the vent valve (fig. 9-21, #2) over the bolts. Apply the nuts to the bolts. Tighten the bolts. Manhole Air Intake The manhole air intake consists of a one-piece, round, flanged sheet steel dust restrictor ring, a one-piece, round, fabricated steel bar, an inside screen ring, and a copper insect screen. The insect screen is attached to the screen ring by two outside rings, formed from steel bars. Flange bolts, inserted through the manhole cover, a dust restrictor ring, and steel pipe sleeve spacers attach the air intake to the manhole dome. Wrap the insect screen around the outside of the inside screen ring. Join the ends of the screen with the copper wire weave. Install an outside screen ring at the top and the bottom of the insect screen to hold it in place. Make sure the screen is not knocked out of position. Tighten the bolts. Install the screen ring on the top flange of the dome (fig. 9-20, #3). Insert the flange bolts through the cover, the dust restrictor ring, the steel pipe sleeve spacers, and the top flange of the dome (fig. 9-20, #3), in that order. Apply the nuts to the bolts and tighten. Place the manhole cover gasket over the bolt holes at the opening in the cover. Insert 1/2- by 1 l/2-inch bolts through the two bolt hole channels. Work through the l0-inch hole and insert the bolts through the cover and the gasket. Install the blind hatch flange over the bolts. Apply the nuts to the bolts. Tighten the bolts. Outside Ladder The outside ladder consists of one bolted steel angle section. The top of the ladder is attached to the deck by two fabricated steel handrails. Two bolted steel angle braces support the ladder at the bottom chime of a stave. Place the left side ladder section and the right side ladder section with similar bolting legs facing each other on top of several pieces of blocking of sufficient length to support both sections and spaced wide enough apart to install a ladder step (fig. 9-21, #6). Select the bottom end of the ladder. Seven steps make up the assembled section. Insert 1/2- by l-inch bolts through the ends of the step and the sections, in that order. Install a nut on each bolt protruding through the sections. Tighten the bolts after all of the steps are installed. Install the braces at the bottom of the section. The leg with three bolt holes near each end of the braces is attached at the outside face of the vertical legs of the sections. Insert a bolt through the end bolt hole in the sections and the brace. Install the nuts on the bolts. Finger tighten the bolts. Install the handrails at the top of the sections. Insert the bolts through the horizontal legs of the sections and the rails, in that order. Install the nuts to the bolts. Tighten the bolts. 9-13