b. Determine which end of rails (1 and 2) will be
long enough to support both rails and wide enough apart
to insert ladder step (4).
the bottom. Install steps (4) from bottom toward top of
c. Insert /2-by 1-inch bolts (3) through ends of step
(4) and rails (1 and 2) in that order. Secure bolts with
nuts (5). Tighten bolts after installing all steps.
d. Face the 28-bolthole flange of the manhole
dome (7) and slide dome over top of rails. Use drift pin
and aline the three boltholes at top of rails with similar
holes in side of dome. Insert 1/2 -by 11/4 -inch bolts (6)
through rails and dome in that order. Secure the bolts
with washers and nuts; tighten the bolts.
e. Install a 30-bolthole gasket on the inside face of
the bottom flange of dome. Insert ½/-by 11/4-inch bolts
through flange and gasket. Gasket material will hold
bolts in place.
3-12. Installation of Ladder
a. Raise ladder assembly (fig. 3-19) and set front
legs of rails (1 and 2) against the inside face of the
vertical leg of brace (8).
b. Insert bolts (3) through the rails and brace in
c. Install nuts (5) on bolts (3). Tighten the bolts.
LEFT LADDER SUPPORT RAIL
RIGHT LADDER SUPPORT RAIL
Figure 3-19. Center support ladder assembled.
Section IV. ASSEMBLY AND INSTALLATION OF TANK DECK
valve, one is assembled with a blind flange, and the
remaining plate is fitted with a liquid level indicator.
The assembled deck consists of six, tapered, flat, steel
All plates are interchangeable.
plates (1, fig. 3-20). There are three special plates: one
plate is fitted with a pressure vacuum