R307-327-6. Retrofits for Floating Roof Tanks

(1) Except where specifically exempted in (3) below, all existing external floating roof tanks with capacities greater than 950 barrels (40,000 gals) shall be retrofitted with a continuous secondary seal extending from the floating roof to the tank wall (a rim-mounted secondary seal) if:

(a) The tank is a welded tank, the true vapor pressure of the contained liquid is 27.6 kPa (4.0 psia) or greater and the primary seal is one of the following:

(i) A metallic type shoe seal, a liquid-mounted foam seal, a liquid-mounted liquid-filled seal, or

(ii) Any other primary seals that can be demonstrated equivalent to the above primary seals.

(b) The tank is a riveted tank, the true vapor pressure of the contained liquid is 10.5 kPa (1.5 psia) or greater, and the primary seal is as described in (a) above.

(c) The tank is a welded or riveted tank, the true vapor pressure of the contained liquid is 10.5 kPa (1.5 psia) or greater and the primary seal is vapor-mounted. When such primary seal closure device can be demonstrated equivalent to the primary seals described in (a) above, these processes apply.

(2) The owner or operator of a storage tank subject to this rule shall ensure that all the seal closure devices meet the following requirements:

(a) There shall be no visible holes, tears, or other openings in the seals or seal fabric.

(b) The seals must be intact and uniformly in place around the circumference of the floating roof between the floating roof and the tank wall.

(c) For vapor mounted primary seals, the accumulated area of gaps between the secondary seal and the tank wall shall not exceed 21.2 cm² per meter of tank diameter (1.0 in² per ft. of tank diameter) and the width of any gap shall not exceed 1.27 cm (1/2 in.). The owner or operator shall measure the secondary seal gap annually and make a record of the measurement.

(3) The following are specifically exempted from the requirements of (1) above:

(a) External floating roof tanks having capacities less than 10,000 barrels (420,000 gals) used to store produced crude oil and condensate prior to custody transfer.

(b) A metallic type shoe seal in a welded tank that has a secondary seal from the top of the shoe seal to the tank wall (a shoe mounted secondary seal).

(c) External floating roof tanks storing waxy, heavy pour crudes.

(d) External floating roof tanks with a closure seal device or other devices installed that will control volatile organic compounds (VOC) emissions with an effectiveness equal to or greater than the seals required in (1) above. It shall be the responsibility of the owner or operator of the source to demonstrate the effectiveness of the alternative seals or devices to the director. No exemption under (3) shall be granted until the alternative seals or devices are approved by the director.