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Subchapter 1. Unfired Pressure Vessel Safety Orders
Article 7. Compressed and Liquefied Natural Gas System

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§531. Location of Storage Tanks and Regulating Equipment.

(a) General.

(1) Except as provided elsewhere in these Orders, tanks, cylinders and regulating equipment used with natural gas storage and/or dispensing installations shall be located outside of buildings. Each individual tank or cylinder used for storage or dispensing natural gas shall be located with respect to the nearest important building, or line or adjoining property which may be built upon, or source of ignition, in accordance with the following table:
Capacity Per Storage Tank or Bank of Cylinders U.S. Gallons Minimum Distance In Feet Distance Between Above Ground Storage Tanks, Feet
To 500 10 3
501 To 2,000 25 3
2,001 To 30,000 50 5
30,001 To 70,000 75 1/4 of Sum of Diameter of Adjacent Tanks with
70,001 To 90,000 100 a Minimum of 5 Feet

NOTE: At the discretion of the Division, tanks may be located a lesser distance from important buildings constructed of concrete or masonry materials.

(2) No stationary storage vessel shall be located less than 10 feet from the nearest street line or sidewalk, nor less than 50 feet from the nearest rail of any railroad main track.

The distance between underground tanks shall be not less than 12 inches.

(3) Except as permitted in Section 543, filling connections shall not be located less than 10 feet from any opening into or under a building closed on more than 3 sides for filling connections 1/2-inch pipe size or less than 15 feet for larger sized filling connections.

(4) Readily ignitible material shall not be permitted within 10 feet of any stationary vessel or vaporizer.

(5) Regulators which are vented to atmosphere shall be installed in such a manner that moisture cannot enter the vent and accumulate above the diaphragm. Where the regulator vent may be obstructed due to rain, snow or icing conditions, shields, hoods or other suitable devices shall be provided to guard against closing the vent opening.

(b) Compressed Natural Gas.

(1) Multiple cylinder units or groups stored in the vertical position shall be limited to a width of no more than 4 cylinders. Units or groups stored in the horizontal position shall be limited to a height of 6 and a width of 4 cylinders. When stacked horizontally, the units or groups shall be separated by not less than 3 feet.

(2) No cylinder filling platform shall be located less than 10 feet from any storage tank, or 25 feet from the nearest important building or line of adjoining property that may be built upon. At the discretion of the Division, cylinder filling platforms may be located a lesser distance from important buildings constructed of concrete or masonry materials.

(c) Liquefied Natural Gas.

(1) All aboveground LNG tanks larger than 2,000 gallons shall have diked impounding areas or equivalent in accordance with Pamphlet 59-A of the National Fire Protection Association.

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