(b) The owner or operator who elects to use a fixed roof and an internal floating roof, as defined in § 63.111 , to comply with the requirements of paragraph (a)(1) of this section shall comply with the requirements specified in paragraphs (b)(1) through (7) of this section. Note: The intent of paragraphs (b)(1) and (2) of this section is to avoid having a vapor space between the floating roof and the stored liquid for extended periods. Storage vessels may be emptied for purposes such as routine storage vessel maintenance, inspections, petroleum liquid deliveries, or transfer operations. Storage vessels where liquid is left on walls, as bottom clingage, or in pools due to floor irregularity are considered completely empty.
(1) The internal floating roof shall be floating on the liquid surface at all times except when the floating roof must be supported by the leg supports during the periods specified in paragraphs (b)(1)(i) through (b)(1)(iii) of this section. (i) During the initial fill.(ii) After the vessel has been completely emptied and degassed.(iii) When the vessel is completely emptied before being subsequently refilled.(2) When the floating roof is resting on the leg supports, the process of filling, emptying, or refilling shall be continuous and shall be accomplished as soon as practical.(3) Each internal floating roof shall be equipped with a closure device between the wall of the storage vessel and the roof edge. Except as provided in paragraph (b)(3)(iv) of this section, the closure device shall consist of one of the devices listed in paragraph (b)(3)(i), (b)(3)(ii), or (b)(3)(iii) of this section. (i) A liquid-mounted seal as defined in § 63.111 of this subpart.(ii) A metallic shoe seal as defined in § 63.111 of this subpart.(iii) Two seals mounted one above the other so that each forms a continuous closure that completely covers the space between the wall of the storage vessel and the edge of the internal floating roof. The lower seal may be vapor- mounted, but both must be continuous seals.(iv) If the internal floating roof is equipped with a vapor-mounted seal as of December 31, 1992, the requirement for one of the seal options specified in paragraphs (b)(3)(i), (b)(3)(ii), and (b)(3)(iii) of this section does not apply until the earlier of the dates specified in paragraphs (b)(3)(iv)(A) and (b)(3)(iv)(B) of this section.(A) The next time the storage vessel is emptied and degassed.(B) No later than 10 years after April 22, 1994.(4) Automatic bleeder vents are to be closed at all times when the roof is floating, except when the roof is being floated off or is being landed on the roof leg supports.(5) Except as provided in paragraph (b)(5)(viii) of this section, each internal floating roof shall meet the specifications listed in paragraphs (b)(5)(i) through (b)(5)(vii) of this section.(i) Each opening in a noncontact internal floating roof except for automatic bleeder vents (vacuum breaker vents) and rim space vents is to provide a projection below the liquid surface.(ii) Except as specified in paragraph (b)(5)(ix) of this section, each opening in the internal floating roof except for leg sleeves, automatic bleeder vents, rim space vents, column wells, ladder wells, sample wells, and stub drains shall be equipped with a cover or lid. The cover or lid shall be equipped with a gasket.(iii) Each penetration of the internal floating roof for the purposes of sampling shall be a sample well. Each sample well shall have a slit fabric cover that covers at least 90 percent of the opening.(iv) Each automatic bleeder vent shall be gasketed.(v) Each rim space vent shall be gasketed.(vi) Each penetration of the internal floating roof that allows for passage of a ladder shall have a gasketed sliding cover.(vii) Each penetration of the internal floating roof that allows for passage of a column supporting the fixed roof shall have a flexible fabric sleeve seal or a gasketed sliding cover.(viii) If the internal floating roof does not meet any one of the specifications listed in paragraphs (b)(5)(i) through (b)(5)(vii) of this section as of December 31, 1992, the requirement for meeting those specifications does not apply until the earlier of the dates specified in paragraphs (b)(5)(viii)(A) and (b)(5)(viii)(B) of this section. (A) The next time the storage vessel is emptied and degassed.(B) No later than 10 years after April 22, 1994.(ix) For each source as defined in § 63.101 , beginning no later than the compliance dates specified in § 63.100(k)(10) , paragraph (b)(5)(i) of this section no longer applies. Instead, each opening in the internal floating roof except those for automatic bleeder vents (vacuum breaker vents), rim space vents, leg sleeves, and deck drains shall be equipped with a deck cover. The deck cover shall be equipped with a gasket between the cover and the deck.(x) For each source as defined in § 63.101 , beginning no later than the compliance dates specified in § 63.100(k)(10) , each opening for an unslotted guidepole shall be equipped with a pole wiper, and each unslotted guidepole shall be equipped with a gasketed cap on the top of the guidepole.(xi) For each source as defined in § 63.101 , beginning no later than the compliance dates specified in § 63.100(k)(10) , each opening for a slotted guidepole shall be equipped with one of the control device configurations specified in paragraphs (b)(5)(xi)(A) and (B) of this section. (A) A pole wiper and a pole float. The wiper or seal of the pole float shall be at or above the height of the pole wiper.(B) A pole wiper and a pole sleeve.(xii) Each unslotted guidepole cap shall be closed at all times except when gauging the liquid level or taking liquid samples.(6) Each cover or lid on any opening in the internal floating roof shall be closed (i.e., no visible gaps), except when the cover or lid must be open for access. Covers on each access hatch and each gauge float well shall be bolted or fastened so as to be air-tight when they are closed. Rim space vents are to be set to open only when the internal floating roof is not floating or when the pressure beneath the rim seal exceeds the manufacturer's recommended setting.