CENTER LADDER SUPPORTS.The center ladder is the center support for the tank deck. The ladder is adjustable and is used to align the deck section bolt holes and provide the required slope to the tank deck

The ladder consists of two ladder braces, two ladder rails, four ladder steps, steel angles, and a flanged manhole that supports the tank deck

TANK DECKThe tank deck is made up of six sections, extending radially from the tank center ladder support to the top chime of the single ring of side staves. Each deck section has an integral formed flange along its right edge when viewed from the large end toward the small end of the deck section. The flanged side of the deck section acts as a supporting rafter for the deck section. A bolt retainer angle is attached to the inside face of each deck section, flanged to retain the radial seam joint bolts that are installed near the right edge of each deck section.

SPECIAL SECTIONS.The tank bottom has one special section, fitted with a blind opening. All of the staves are special sections (fig. 9-3). One section is for a cleanout cover, and the other five sections are used for pipe connections. The tank deck has three special sections. One section is for a combination thief hatch and vent, one section has a blind hatch, and one section has a liquid level indicator.

EMERGENCY VENT.Each tank is equipped with an 8-inch emergency vent, bolted to the top cover of the manhole attached to the top of the center ladder supports.

OUTSIDE LADDER.Each tank is equipped with an outside ladder for access to the deck The ladder is bolted to the bottom and top chimes of a side stave and is usually located near a tank thief and vent.

250-Barrel Tank

The 250-barrel tank has a capacity of 10,500 gallons of liquid, and the fabrication is similar to the 100-barrel tank. The tank bottom consists of ten wedge-shaped plates, assembled radially around a one-piece center section, as shown in figure 9-4. The inside diameter is 15 feet 4 5/8 inches and is 8 feet 1/2 inch high at the sidewall.

SIDE STAVES.The side staves consist of ten curved, vertical sections, arranged in a single ring. The staves are chimed (flanged) at the top and bottom of each section with the left end of each chime offset so the vertical seams overlap. The bottom chime bolt holes are patterned to match the outer edge bolt holes in the tank bottom. The vertical seams have one row of bolt holes.

TANK DECK.The tank deck is made up of ten sections, extending radially from the tank center ladder support to the top chime of the single ring of side staves. Each deck section has an integral formed flange along its right edge when viewed from the large

Figure 9-3.-Layout of the staves around the tank bottom.