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|  MIL-T-62032H
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3.5.9 Manholes. Each compartment of the tank shall be equipped with a round manhole
opening not less than 19 inches in diameter. A lightweight, liquid-tight, easy opening manhole
cover or a bolted cover with a liquid-tight easy opening fill cover not less than 10 inches in
diameter shall be supplied. The manhole shall be fully compatible with the use of a
Parker-Hannifin Model F428A vapor-recovery adapter cover (to be in place only when
top-loading). All materials used shall be resistant to corrosion and to deterioration from contact
with the product fuel. Normal breathing venting may be incorporated into the manhole cover
(see 3.5.11). If the cover is hinged, the hinge shall be forward-mounted and the cover shall have
self-latching catches. The manhole cover shall have provisions for a padlock. When specified
(see 6.2), a 2-inch National Pipe Thread (NPT) coupling and plug shall be provided in the tank,
near the manhole cover, to permit future installation of a second fuel level-sensing device.
3.5.10 Capacity marker. A capacity marker or indicator disk of corrosion-resistant
construction shall be installed at the side of each manhole. The marker shall be located so as not
to interfere with the vapor recovery adapter cover specified in 3.5.9. The marker shall be set to
indicate rated tank capacity 1 percent.
3.5.11 Vents. Each tank compartment shall be vented to comply with the requirements
of 49 CFR, Section 178.341, Specification MC-306, and the additional requirements specified
herein.
3.5.11.1 Normal venting pressure limits. The lower opening limits for normal venting
(inbreathing, outbreathing) shall comply with the opening limits required by the California Air
Resources Board for vapor recovery, as summarized herein:
(a) The entire tank and venting system shall be sufficiently vaportight, such that a
pressure change of not more than 1 inch of water shall occur within 5 minutes when
the tank is pressurized to 18 inches of water (gage) or evacuated to 6 inches of water
(gage);
(b) The outbreathing pressure vents shall remain closed as tank compartment pressure is
increased above 18 inches of water (gage), but shall open before compartment
pressure reaches 27.7 inches of water (1 psig);
(c) The inbreathing vacuum vents shall remain closed until tank compartment vacuum
drops below 6 inches of water (gage), but shall open before a vacuum of 10.4 inches
of water (gage) is reached (6 ounces per square inch gage).
3.5.11.2 Normal venting capacity. The normal vents shall have sufficient vapor flow
capacity to permit bottom loading at a rate of 600 gpm, and for types I through IV to permit
loading and unloading through the plumbing system at not less than 200 gpm, all with the
manhole and fill covers closed, without damage and without exceeding the vacuum and pressure
limitations of 49 CFR, section 178.341, specification MC-306 (maximum pressure of 3 psig;
maximum vacuum of 1 psig).
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