19
10. BALLASTING (ADDING LIQUID)
Do not use air pressure to test tanks that contain or have
contained flammable or combustible liquids or vapors, and
do not perform any postinstallation pressure tests. The fuel
and air mixture could explode and cause death or serious
injury. Tanks should be air tested before ballasting.
If product is used as ballast, exercise special care in
handling. Safeguard against sparks, fire or product spills.
Improper handling of product could cause a fire or explo-
sion, and death or serious injury.
When ballasting the tank, make sure the tank is properly
vented. The vent must be large enough to allow the
displaced air to escape. Failure to properly vent the tank
may cause tank damage.
10.1. GENERAL
10.1.1. In most anchoring systems, a tank is not adequately
protected against flotation until the tank is fully backfilled and the
top slab is in place. Therefore, during the installation process,
the tank should be ballasted completely after the backfill is even
with the top of the tank and postinstallation testing has been
successfully completed.
10.1.2. Only under wet-hole conditions should ballast be added
before the backfill is even with the top of the tank.
(See
SECTION 8.)
When filling the tank, make sure the tank is properly vented.
The vent must be large enough to allow the displaced air to
escape.
11. PIPING AND VENTING
11.1. INTERNAL PIPING
11.1.1. All piping must conform to all applicable codes and
standards.
(See SECTION 1.)
All internal piping must be at least 4 inches [6 inches for
12-foot-diameter tanks] from the tank bottom.
All metal fittings and other metal components must be coated
to protect against corrosion.
11.1.2.
Refer to FIGURE 11-1 along with TABLE 11-1
to
determine the correct dimensions for sizing internal piping.
FIGURE 11-1
TABLE 11-1
11.2. EXTERNAL PIPING
When pressure testing the external piping, the tank must be
isolated from all piping. The test pressures for external
piping could cause tank failure, and result in death or
serious injury.
When extending monitoring or vapor-recovery piping to the
surface, make sure the at-grade fittings are different from
any fill fittings and will not accept standard fill hoses.
11.3. VENTING TANK
All underground tanks/compartments must be vented to
atmosphere for proper operations. Failure to vent could
result in death or serious injury.
11.3.1. In the double-wall and triple-wall tank, the primary tank is
designed to operate at atmospheric pressure.
Tank Diameter
4’
49 1/4”
54 1/2”
48”
49 1/2”
55”
48”
51 1/2”
56 5/8”
48”
6’
73”
78”
71 3/8”
72 3/4”
77 3/4”
70 5/8”
75 1/8”
80 1/4”
71 3/8”
8’
92”
98”
91 3/16”
91 1/2”
97 1/4”
90 5/8”
95 3/8”
100 1/2”
91 3/16”
10’
121”
126”
119 3/16”
120”
125 3/4”
118 1/2”
123 1/2”
128 5/8”
119 3/16”
12’
138 1/4”
143 1/4”
136 5/8”
_____
_____
_____
_____
_____
_____
Interior
Dimensions
in FIGURE
11 1
“A”
“B”
“C”
“D”
“E”
“F”
“G”
“H”
“I”
B & E
A & D
H
G
D
C
B
E
A
F
I
G
H
Single-Wall
Double-Wall II
Ribbed Outer Wall
Double-Wall I
Smooth Outer Wall
Dimension Line
Single-Wall & Double-Wall II
Dimension Line
Double-Wall I
Note:
1. All fitting dimensions are measured from the top of a
service fitting to the inside bottom of the tank and include
gauge-plate clearance.
2. Interior diameters do not include gauge-plate clearance.
