Ala. Admin. Code r. 335-3-6-.23

Current through Register Vol. 43, No. 1, October 31, 2024

Section 335-3-6-.23 - Petroleum Liquid Storage In External Floating Roof Tanks

(1) For the purpose of this Rule, the following definitions apply:

(a) "Condensate" shall mean hydrocarbon liquid separated from natural gas which condenses due to changes in the temperature and/or pressure and remains liquid at standard conditions.

(b) "Crude Oil" shall mean a naturally occurring mixture which consists of hydrocarbons and sulfur, nitrogen and/or oxygen derivatives of hydrocarbons which is a liquid in the reservoir at standard conditions.

(c) "Custody Transfer" shall mean the transfer of produced crude oil and/or condensate, after processing and/or treating in the producing operations, from storage tanks or automatic transfer facilities to pipelines or any other forms of transportation.

(d) "External Floating Roof" shall mean a storage vessel cover in an open top tank consisting of a double deck or pontoon single deck which rests upon and is supported by the petroleum liquid being contained and is equipped with a closure seal or seals to close the space between the roof edge and tank wall.

(e) "Liquid-Mounted Seal" shall mean a primary seal mounted in continuous contact with the liquid between the tank wall and the floating roof around the circumference of the tank.

(f) "Petroleum Liquids" mean crude oil, condensate, and any finished or intermediate products manufactured or extracted in a petroleum refinery.

(g) "Vapor-Mounted Seal" shall mean any primary seal mounted continuously around the circumference of the tank. The annular vapor space is bounded by the bottom of the primary seal, the tank wall, the liquid surface, and the floating roof.

(h) "Waxy, Heavy Pour Crude Oil" shall mean a crude oil with a pour point of 10° C (50° F) or higher as determined by the American Society for Testing Materials Standard D 97-66, "Test for Pour Point of Petroleum Oils."

(2) This Rule shall apply to all petroleum liquid storage vessels equipped with external floating roofs, having capacities greater than 150,000 liters (40,000 gallons).

(3) This Rule does not apply to petroleum liquid storage vessels which:

(a) are used to store waxy, heavy pour crude oil;

(b) have capacities less than 1,600,000 liters (423,000 gallons) and are used to store produced crude oil and condensate prior to custody transfer;

(c) contain a petroleum liquid with a true vapor pressure of less than 10.5 kPa (1.5 psia);

(d) contain a petroleum liquid with a true vapor pressure less than 27.6 kPa (4.0 psia); and,

1. are of welded construction; and,

2. presently possess a metallic-type shoe seal, a liquid-mounted foam seal, a liquid-mounted liquid filled type seal, or other closure device of demonstrated equivalence approved by the Director; or,

(e) are of welded construction, equipped with a metallic-type shoe primary seal and has a secondary seal from the top of the shoe seal to the tank wall (shoe-mounted secondary seal).

(4) No owner or operator of a petroleum liquid storage vessel subject to this Rule shall store a petroleum liquid in that vessel unless:

(a) the vessel has been fitted with:

1. a continuous secondary seal extending from the floating roof to the tank wall (rim-mounted secondary seal); or

2. a closure or other device which controls VOC emissions with an effectiveness equal to or greater than a seal required under subparagraph (a)1. of this paragraph above, as approved by the Director.

(b) All seal closure devices meet the following requirements:

1. there are no visible holes, tears, or other openings in the seal(s) or seal fabric;

2. the seal(s) are intact and uniformly in place around the circumference of the floating roof between the floating roof and tank wall; and

3. for vapor mounted seals, the area of accumulated gaps between the secondary seal and the tank wall are determined by the method in Rule 335-3-6-.16(8)(c), and shall not exceed 21.2 square centimeters per meter of tank diameter (1.0 square inch per foot of tank diameter)

(c) All openings in the external floating roof, except for automatic bleeder vents, rim space vents, and leg sleeves, are:

1. equipped with covers, seals, or lids in the closed position except when the openings are in actual use; and

2. equipped with projections into the tank which remain below the liquid surface.

(d) Automatic bleeder vents are closed at all times except when the roof is floated off or landed on the roof leg supports;

(e) Rim vents are set to open when the roof is being floated off the leg supports or at the manufacturer's recommended setting; and,

(f) Emergency roof drains are provided with slotted membrane fabric covers or equivalent covers which cover at least ninety percent (90%) of the area of the opening.

(5) The owner or operator of a petroleum liquid storage vessel with an external floating roof subject to this Rule shall:

(a) perform routine inspections semi-annually in order to ensure compliance with paragraph (4) of this Rule, and the inspections shall include a visual inspection of the secondary seal gap;

(b) measure the secondary seal gap annually in accordance with Rule 335-3-6-.16(8) when the floating roof is equipped with a vapor-mounted primary seal; and,

(c) maintain records of the throughput quantities and types of volatile petroleum liquids stored.

(6) The owner or operator of a petroleum liquid storage vessel with an external floating roof not subject to this Rule, but containing a petroleum liquid with a true vapor pressure greater than 7.0 kPa (1.0 psia), shall maintain records of the average monthly storage temperature, the type of liquid, throughput quantities, and the maximum true vapor pressure for all petroleum liquids with a true vapor pressure greater than 7.0 kPa.

(7) The owner or operator of a petroleum liquid storage vessel subject to this Rule shall submit to the Director, as a minimum, an annual report detailing the results of routine monthly inspections, secondary seal gap measurements, and the amounts and physical properties of stored liquids.

(8) Copies of all records and reports under paragraphs (5), (6), and (7) of this Rule shall be retained by the owner or operator for a minimum of two (2) years after the date on which the record was made or the report submitted.

Author: Wm. Gerald Hardy

Ala. Admin. Code r. 335-3-6-.23

Effective Date: April 19, 1984. Amended: Filed October 17, 1996; effective November 21, 1996.

Statutory Authority:Code of Ala. 1975, §§ 22-28-14, 22-22A-5, 22-22A-6, 22-22A-8.