Pennsylvania Code › Title 34 - LABOR AND INDUSTRY › Part I - Department of Labor and Industry › Chapter 14a - STORAGE AND USE OF FLAMMABLE AND COMBUSTIBLE LIQUIDS › Subchapter A - GENERAL PROVISIONS › UNDERGROUND STORAGE › Section 14a.25 - Vents for underground tanks

Current through Register Vol. 54, No. 28, July 13, 2024
(a)
					 Vent pipes from underground storage tanks storing class I liquids shall be so
					 located that the discharge point is outside of buildings, higher than the
					 fill-pipe opening, and not less than 12 feet above the adjacent ground level.
					 Vent pipes shall discharge only upward in order to disperse vapors. Vent pipes
					 shall not be obstructed by devices provided for vapor recovery or other
					 purposes unless the tank and associated piping and equipment are otherwise
					 protected to limit back-pressure development to less than the maximum working
					 pressure of the tank and equipment by the provision of pressure-vacuum vents,
					 rupture discs, or other tank-venting devices installed in the tank-vent lines.
					 Vent outlets and devices shall be protected to minimize the possibility of
					 blockage from weather, dirt, or insect nests and shall be so located and
					 directed that flammable vapors will not accumulate or travel to an unsafe
					 location, enter building openings, or be trapped under eaves. Tanks containing
					 class IA liquids shall be equipped with pressure and vacuum venting devices
					 which shall be normally closed except when venting under pressure or vacuum
					 conditions. Tanks storing class IB or class IC liquids shall be equipped with
					 pressure-vacuum vents or with listed flame arresters. Tanks storing gasoline
					 are exempt from the requirements for pressure and vacuum venting devices,
					 except as required to prevent excessive back pressure, or flame arresters,
					 provided the vent does not exceed 3 inches nominal inside diameter.
(b) Vent pipes from tanks storing class II or
					 class III liquids shall terminate outside of building and higher than the
					 fill-pipe opening. Vent outlets shall be above normal snow level. They may be
					 fitted with return bends, coarse screens, or other devices to minimize ingress
					 of foreign material. Vent piping shall be constructed in accordance with §
											14a.51 (relating to scope and
					 application).
(c) Tank-venting
					 systems shall be provided with sufficient capacity to prevent blowback of vapor
					 or liquid at the fill opening while the tank is being filled. Vent pipes shall
					 not be less than 1¼ inch nominal inside diameter. The required venting
					 capacity depends upon the filling or withdrawal rate, whichever is greater, and
					 the vent-line length. Unrestricted vent piping sized in accordance with the
					 following table will prevent back-pressure development in tanks from exceeding
					 2.5 psig Where tank venting devices are installed in vent lines, their flow
					 capacities shall be determined in accordance with §
											14a.8(b)(6)
					 (relating to vents).
Maximum Flow in GPM
Length of Pipe-Vent Lines of 50 feet, 100 feet, and 200
								  feet of pipe plus 7 ells-(in feet)
50
100
200
Vent Line Diameters
								  (in inches)
100
1 1/4
1 1/4
1
								  1/4
200
1 1/4
1 1/4
1 1/4
300
1 1/4
1 1/4
1 1/2
400
1 1/4
1 1/2
2
500
1 1/2
1 1/2
2
600
1 1/2
2
2
700
2
2
2
800
2
2
3
900
2
2
3
1000
2
2
3
(d) Vent pipes shall be so laid as to drain
					 toward the tank without sags or traps in which liquid can collect. They shall
					 be located so that they will not be subjected to physical damage. The tank end
					 of a vent pipe shall enter the tank through the top.
(e) When tank vent piping is manifolded, pipe
					 sizes shall be such as to discharge, within the pressure limitations of the
					 system, the vapors they can be required to handle when manifolded tanks are
					 filled simultaneously; except that, for service stations, the capacity of
					 manifolded vent piping shall be sufficient to discharge vapors generated when
					 two manifolded tanks are simultaneously filled.
(f) Vent piping for tanks storing class I
					 liquids shall not be manifolded with vent piping for tanks storing class II or
					 class III liquids, unless positive means are provided to prevent the vapors
					 from class I liquids from entering tanks storing class II or class III liquids,
					 to prevent contamination and possible change in classification of the less
					 volatile liquid.
(g) Where tanks
					 are filled by the use of a pump through tight connections, a vent pipe not less
					 in size than the discharge of the pump shall be used. Under no circumstances
					 shall the vent pipe diameter be less than 1¼ inches nominal inside
					 diameter.
(h) The design and
					 location of vent pipe systems (except those designed for areas of mandatory
					 vapor recovery) shall take into consideration the proximity of neighboring
					 buildings with respect to flammable and noxious vapors.
This section cited in 34 Pa. Code §
													14a.21 (relating to location); 34
						  Pa. Code §
													14a.141 (relating to scope and
						  application); 34 Pa. Code §
													14a.151 (relating to scope and
						  application); and 34 Pa. Code §
													14a.161 (relating to general
						  provisions).