1910.110—Storage and handling of liquefied petroleum gases.
(1)
API-ASME container—A container constructed in accordance with the requirements of paragraph (b)(3)(iii) of this section.
(2)
ASME container—A container constructed in accordance with the requirements of paragraph (b)(3)(i) of this section.
(3)
Container assembly—An assembly consisting essentially of the container and fittings for all container openings, including shutoff valves, excess flow valves, liquid-level gaging devices, safety relief devices, and protective housing.
(4)
Containers—All vessels, such as tanks, cylinders, or drums, used for transportation or storing liquefied petroleum gases.
(6)
DOT container—A container constructed in accordance with the applicable requirements of 49 CFR chapter 1.
(7)
“Liquified petroleum gases”—“LPG” and “LP-Gas”—Any material which is composed predominantly of any of the following hydrocarbons, or mixtures of them; propane, propylene, butanes (normal butane or iso-butane), and butylenes.
(8)
Movable fuel storage tenders or farm carts—Containers not in excess of 1,200 gallons water capacity, equipped with wheels to be towed from one location of usage to another. They are basically nonhighway vehicles, but may occasionally be moved over public roads or highways. They are used as a fuel supply for farm tractors, construction machinery and similar equipment.
(11)
Systems—an assembly of equipment consisting essentially of the container or containers, major devices such as vaporizers, safety relief valves, excess flow valves, regulators, and piping connecting such parts.
(12)
Vaporizer-burner—an integral vaporizer-burner unit, dependent upon the heat generated by the burner as the source of heat to vaporize the liquid used for dehydrators or dryers.
(13)
Ventilation, adequate—when specified for the prevention of fire during normal operation, ventilation shall be considered adequate when the concentration of the gas in a gas-air mixture does not exceed 25 percent of the lower flammable limit.
(14)
Approved—unless otherwise indicated, listing or approval by a nationally recognized testing laboratory. Refer to § 1910.7 for definition of nationally recognized testing laboratory.
(16)
DOT Specifications—regulations of the Department of Transportation published in 49 CFR chapter I.
(b) Basic rules—
(1) Odorizing gases.
All liquefied petroleum gases shall be effectively odorized by an approved agent of such character as to indicate positively, by distinct odor, the presence of gas down to concentration in air of not over one-fifth the lower limit of flammability. Odorization, however, is not required if harmful in the use of further processing of the liquefied petroleum gas, or if odorization will serve no useful purpose as a warning agent in such use or further processing.
(ii)
The odorization requirement of paragraph (b)(1)(i) of this section shall be considered to be met by the use of 1.0 pounds of ethyl mercaptan, 1.0 pounds of thiophane or 1.4 pounds of amyl mercaptan per 10,000 gallons of LP-Gas. However, this listing of odorants and quantities shall not exclude the use of other odorants that meet the odorization requirements of paragraph (b)(1)(i) of this section.
(2) Approval of equipment and systems.
(i)
Each system utilizing DOT containers in accordance with 49 CFR part 178 shall have its container valves, connectors, manifold valve assemblies, and regulators approved.
(ii)
Each system for domestic or commercial use utilizing containers of 2,000 gallons or less water capacity, other than those constructed in accordance with 49 CFR part 178, shall consist of a container assembly and one or more regulators, and may include other parts. The system as a unit or the container assembly as a unit, and the regulator or regulators, shall be individually listed.
(iii)
In systems utilizing containers of over 2,000 gallons water capacity, each regulator, container valve, excess flow valve, gaging device, and relief valve installed on or at the container, shall have its correctness as to design, construction, and performance determined by listing by a nationally recognized testing laboratory. Refer to § 1910.7 for definition of nationally recognized testing laboratory.
(3) Requirements for construction and original test of containers.
(i)
Containers used with systems embodied in paragraphs (d), (e), (g), and (h) of this section, except as provided in paragraphs (e)(3)(iii) and (g)(2)(i) of this section, shall be designed, constructed, and tested in accordance with the Rules for Construction of Unfired Pressure Vessels, section VIII, Division 1, American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, 1968 edition, which is incorporated by reference as specified in § 1910.6.
(ii)
Containers constructed according to the 1949 and earlier editions of the ASME Code do not have to comply with paragraphs U-2 through U-10 and U-19 thereof. Containers constructed according to paragraph U-70 in the 1949 and earlier editions are not authorized.
(iii)
Containers designed, constructed, and tested prior to July 1, 1961, according to the Code for Unfired Pressure Vessels for Petroleum Liquids and Gases, 1951 edition with 1954 Addenda, of the American Petroleum Institute and the American Society of Mechanical Engineers, which is incorporated by reference as specified in § 1910.6, shall be considered in conformance. Containers constructed according to API-ASME Code do not have to comply with section I or with appendix to section I. Paragraphs W-601 to W-606 inclusive in the 1943 and earlier editions do not apply.
(iv)
The provisions of paragraph (b)(3)(i) of this section shall not be construed as prohibiting the continued use or reinstallation of containers constructed and maintained in accordance with the standard for the Storage and Handling of Liquefied Petroleum Gases NFPA No. 58 in effect at the time of fabrication.
(v)
Containers used with systems embodied in paragraph (b), (d)(3)(iii), and (f) of this section, shall be constructed, tested, and stamped in accordance with DOT specifications effective at the date of their manufacture.
(4) Welding of containers.
(i)
Welding to the shell, head, or any other part of the container subject to internal pressure, shall be done in compliance with the code under which the tank was fabricated. Other welding is permitted only on saddle plates, lugs, or brackets attached to the container by the tank manufacturer.
(ii)
Where repair or modification involving welding of DOT containers is required, the container shall be returned to a qualified manufacturer making containers of the same type, and the repair or modification made in compliance with DOT regulations.
(5) Markings on containers.
(i)
Each container covered in paragraph (b)(3)(i) of this section, except as provided in paragraph (b)(3)(iv) of this section shall be marked as specified in the following:
(a) With a marking identifying compliance with, and other markings required by, the rules of the reference under which the container is constructed; or with the stamp and other markings required by the National Board of Boiler and Pressure Vessel Inspectors.
(b) With notation as to whether the container is designed for underground or aboveground installation or both. If intended for both and different style hoods are provided, the marking shall indicate the proper hood for each type of installation.
(c) With the name and address of the supplier of the container, or with the trade name of the container.
(d) With the water capacity of the container in pounds or gallons, U.S. Standard.
(e) With the pressure in p.s.i.g., for which the container is designed.
(f) With the wording “This container shall not contain a product having a vapor pressure in excess of __ p.s.i.g. at 100 °F.,” see subparagraph (14)(viii) of this paragraph.
(g) With the tare weight in pounds or other identified unit of weight for containers with a water capacity of 300 pounds or less.
(h) With marking indicating the maximum level to which the container may be filled with liquid at temperatures between 20 °F. and 130 °F., except on containers provided with fixed maximum level indicators or which are filled by weighing. Markings shall be increments of not more than 20 °F. This marking may be located on the liquid level gaging device.
(i) With the outside surface area in square feet.
(ii)
Markings specified shall be on a metal nameplate attached to the container and located in such a manner as to remain visible after the container is installed.
(iii)
When LP-Gas and one or more other gases are stored or used in the same area, the containers shall be marked to identify their content. Marking shall conform to the marking requirements set forth in § 1910.253(b)(1)(ii).
(6) Location of containers and regulating equipment.
(i)
Containers, and first stage regulating equipment if used, shall be located outside of buildings, except under one or more of the following:
(a) In buildings used exclusively for container charging, vaporization pressure reduction, gas mixing, gas manufacturing, or distribution.
(b) When portable use is necessary and in accordance with paragraph (c)(5) of this section.
(c) LP-Gas fueled stationary or portable engines in accordance with paragraph (e) (11) or (12) of this section.
(d) LP-Gas fueled industrial trucks used in accordance with paragraph (e)(13) of this section.
(e) LP-Gas fueled vehicles garaged in accordance with paragraph (e)(14) of this section.
(f) Containers awaiting use or resale when stored in accordance with paragraph (f) of this section.
(ii)
Each individual container shall be located with respect to the nearest important building or group of buildings in accordance with Table H-23.
| Water capacity per container | Minimum distances | Containers | Underground | Aboveground | Between aboveground containers |
|---|---|---|---|---|---|
| Less than 125 gals. 1 | 10 feet | None | None. | ||
| 125 to 250 gals | 10 feet | 10 feet | None. | ||
| 251 to 500 gals | 10 feet | 10 feet | 3 feet. | ||
| 501 to 2,000 gals | 25 feet 2 | 25 feet 2 | 3 feet. | ||
| 2,001 to 30,000 gals | 50 feet | 50 feet | 5 feet. | ||
| 30,001 to 70,000 gals | 50 feet | 75 feet. 3 | |||
| 70,001 to 90,000 gals | 50 feet | 100 feet. 3 | |||
| 1 If the aggregate water capacity of a multi-container installation at a consumer site is 501 gallons or greater, the minimum distance shall comply with the appropriate portion of this table, applying the aggregate capacity rather than the capacity per container. If more than one installation is made, each installation shall be separated from another installation by at least 25 feet. Do not apply the MINIMUM DISTANCES BETWEEN ABOVE-GROUND CONTAINERS to such installations. | |||||
| 2 The above distance requirements may be reduced to not less than 10 feet for a single container of 1,200 gallons water capacity or less, providing such a container is at least 25 feet from any other LP-Gas container of more than 125 gallons water capacity. | |||||
| 3 1/4 of sum of diameters of adjacent containers. | |||||
(v)
In the case of buildings devoted exclusively to gas manufacturing and distributing operations, the distances required by Table H-23 may be reduced provided that in no case shall containers of water capacity exceeding 500 gallons be located closer than 10 feet to such gas manufacturing and distributing buildings.
(vi)
Readily ignitible material such as weeds and long dry grass shall be removed within 10 feet of any container.
(vii)
The minimum separation between liquefied petroleum gas containers and flammable liquid tanks shall be 20 feet, and the minimum separation between a container and the centerline of the dike shall be 10 feet. The foregoing provision shall not apply when LP-Gas containers of 125 gallons or less capacity are installed adjacent to Class III flammable liquid tanks of 275 gallons or less capacity.
(viii)
Suitable means shall be taken to prevent the accumulation of flammable liquids under adjacent liquified petroleum gas containers, such as by diking, diversion curbs, or grading.
(ix)
When dikes are used with flammable liquid tanks, no liquefied petroleum gas containers shall be located within the diked area.
(7) Container valves and container accessories.
(i)
Valves, fittings, and accessories connected directly to the container including primary shutoff valves, shall have a rated working pressure of at least 250 p.s.i.g. and shall be of material and design suitable for LP-Gas service. Cast iron shall not be used for container valves, fittings, and accessories. This does not prohibit the use of container valves made of malleable or nodular iron.
(ii)
Connections to containers, except safety relief connections, liquid level gaging devices, and plugged openings, shall have shutoff valves located as close to the container as practicable.
(iii)
Excess flow valves, where required shall close automatically at the rated flows of vapor or liquid as specified by the manufacturer. The connections or line including valves, fittings, etc., being protected by an excess flow valve shall have a greater capacity than the rated flow of the excess flow valve.
(iv)
Liquid level gaging devices which are so constructed that outward flow of container contents shall not exceed that passed by a No. 54 drill size opening, need not be equipped with excess flow valves.
(v)
Openings from container or through fittings attached directly on container to which pressure gage connection is made, need not be equipped with shutoff or excess flow valves if such openings are restricted to not larger than No. 54 drill size opening.
(vi)
Except as provided in paragraph (c)(5)(i)(b) of this section, excess flow and back pressure check valves where required by this section shall be located inside of the container or at a point outside where the line enters the container; in the latter case, installation shall be made in such manner that any undue strain beyond the excess flow or back pressure check valve will not cause breakage between the container and such valve.
(vii)
Excess flow valves shall be designed with a bypass, not to exceed a No. 60 drill size opening to allow equalization of pressures.
(viii)
Containers of more than 30 gallons water capacity and less than 2,000 gallons water capacity, filled on a volumetric basis, and manufactured after December 1, 1963, shall be equipped for filling into the vapor space.
(8) Piping—including pipe, tubing, and fittings.
(i)
Pipe, except as provided in paragraphs (e)(6)(i) and (g)(10)(iii), of this section shall be wrought iron or steel (black or galvanized), brass, copper, or aluminum alloy. Aluminum alloy pipe shall be at least Schedule 40 in accordance with the specifications for Aluminum Alloy Pipe, American National Standards Institute (ANSI) H38.7-1969 (ASTM, B241-69), which is incorporated by reference as specified in § 1910.6, except that the use of alloy 5456 is prohibited and shall be suitably marked at each end of each length indicating compliance with American National Standard Institute Specifications. Aluminum Alloy pipe shall be protected against external corrosion when it is in contact with dissimilar metals other than galvanized steel, or its location is subject to repeated wetting by such liquids as water (except rain water), detergents, sewage, or leaking from other piping, or it passes through flooring, plaster, masonry, or insulation. Galvanized sheet steel or pipe, galvanized inside and out, may be considered suitable protection. The maximum nominal pipe size for aluminum pipe shall be three-fourths inch and shall not be used for pressures exceeding 20 p.s.i.g. Aluminum alloy pipe shall not be installed within 6 inches of the ground.
(a) Vapor piping with operating pressures not exceeding 125 p.s.i.g. shall be suitable for a working pressure of at least 125 p.s.i.g. Pipe shall be at least Schedule 40 (ASTM A-53-69, Grade B Electric Resistance Welded and Electric Flash Welded Pipe, which is incorporated by reference as specified in § 1910.6, or equal).
(b) Vapor piping with operating pressures over 125 p.s.i.g. and all liquid piping shall be suitable for a working pressure of at least 250 p.s.i.g. Pipe shall be at least Schedule 80 if joints are threaded or threaded and back welded. At least Schedule 40 (ASTM A-53-69 Grade B Electric Resistance Welded and Electric Flash Welded Pipe or equal) shall be used if joints are welded, or welded and flanged.
(ii)
Tubing shall be seamless and of copper, brass, steel, or aluminum alloy. Copper tubing shall be of type K or L or equivalent as covered in the Specification for Seamless Copper Water Tube, ANSI H23.1-1970 (ASTM B88-69), which is incorporated by reference as specified in § 1910.6. Aluminum alloy tubing shall be of Type A or B or equivalent as covered in Specification ASTM B210-68 (which is incorporated by reference as specified in § 1910.6) and shall be suitably marked every 18 inches indicating compliance with ASTM Specifications. The minimum nominal wall thickness of copper tubing and aluminum alloy tubing shall be as specified in Table H-24 and Table H-25.
Aluminum alloy tubing shall be protected against external corrosion when it is in contact with dissimilar metals other than galvanized steel, or its location is subject to repeated wetting by liquids such as water (except rainwater), detergents, sewage, or leakage from other piping, or it passes through flooring, plaster, masonry, or insulation. Galvanized sheet steel or pipe, galvanized inside and out, may be considered suitable protection. The maximum outside diameter for aluminum alloy tubing shall be three-fourths inch and shall not be used for pressures exceeding 20 p.s.i.g. Aluminum alloy tubing shall not be installed within 6 inches of the ground.
| Standard size (inches) | Nominal outside diameter (inches) | Nominal wall thickness (inches) | |
|---|---|---|---|
| Type K | Type L | ||
| 1/4 | 0.375 | 0.035 | 0.030 |
| 3/8 | 0.500 | 0.049 | 0.035 |
| 1/2 | 0.625 | 0.049 | 0.040 |
| 5/8 | 0.750 | 0.049 | 0.042 |
| 3/4 | 0.875 | 0.065 | 0.045 |
| 1 | 1.125 | 0.065 | 0.050 |
| 11/4 | 1.375 | 0.065 | 0.055 |
| 11/2 | 1.625 | 0.072 | 0.060 |
| 2 | 2.125 | 0.083 | 0.070 |
| 1 Based on data in Specification for Seamless Copper Water Tube, ANSI H23.1-1970 (ASTM B-88-69). | |||
| Note: The standard size by which tube is designated is 1/8 inch smaller than its nominal outside diameter. | |||
| Outside diameter (inches) | Nominal wall thickness (inches) | |
|---|---|---|
| Type A | Type B | |
| 3/8 | 0.035 | 0.049 |
| 1/2 | 0.035 | 0.049 |
| 5/8 | 0.042 | 0.049 |
| 3/4 | 0.049 | 0.058 |
| 1 Based on data in Standard Specification for Aluminum-Alloy Drawn Seamless Coiled Tubes for Special Purpose Applications, ASTM B210-68. | ||
(iii)
In systems where the gas in liquid form without pressure reduction enters the building, only heavy walled seamless brass or copper tubing with an internal diameter not greater than three thirty-seconds inch, and a wall thickness of not less than three sixty-fourths inch shall be used. This requirement shall not apply to research and experimental laboratories, buildings, or separate fire divisions of buildings used exclusively for housing internal combustion engines, and to commercial gas plants or bulk stations where containers are charged, nor to industrial vaporizer buildings, nor to buildings, structures, or equipment under construction or undergoing major renovation.
(iv)
Pipe joints may be screwed, flanged, welded, soldered, or brazed with a material having a melting point exceeding 1,000 °F. Joints on seamless copper, brass, steel, or aluminum alloy gas tubing shall be made by means of approved gas tubing fittings, or soldered or brazed with a material having a melting point exceeding 1,000 °F.
(v)
For operating pressures of 125 p.s.i.g. or less, fittings shall be designed for a pressure of at least 125 p.s.i.g. For operating pressures above 125 p.s.i.g., fittings shall be designed for a minimum of 250 p.s.i.g.
(vi)
The use of threaded cast iron pipe fittings such as ells, tees, crosses, couplings, and unions is prohibited. Aluminum alloy fittings shall be used with aluminum alloy pipe and tubing. Insulated fittings shall be used where aluminum alloy pipe or tubing connects with a dissimilar metal.
(vii)
Strainers, regulators, meters, compressors, pumps, etc., are not to be considered as pipe fittings. This does not prohibit the use of malleable, nodular, or higher strength gray iron for such equipment.
(viii)
All materials such as valve seats, packing, gaskets, diaphragms, etc., shall be of such quality as to be resistant to the action of liquefied petroleum gas under the service conditions to which they are subjected.
(ix)
All piping, tubing, or hose shall be tested after assembly and proved free from leaks at not less than normal operating pressures. After installation, piping and tubing of all domestic and commercial systems shall be tested and proved free of leaks using a manometer or equivalent device that will indicate a drop in pressure. Test shall not be made with a flame.
(x)
Provision shall be made to compensate for expansion, contraction, jarring, and vibration, and for settling. This may be accomplished by flexible connections.
(xi)
Piping outside buildings may be buried, above ground, or both, but shall be well supported and protected against physical damage. Where soil conditions warrant, all piping shall be protected against corrosion. Where condensation may occur, the piping shall be pitched back to the container, or suitable means shall be provided for revaporization of the condensate.
(9) Hose specifications.
(i)
Hose shall be fabricated of materials that are resistant to the action of LP-Gas in the liquid and vapor phases. If wire braid is used for reinforcing the hose, it shall be of corrosion-resistant material such as stainless steel.
(ii)
Hose subject to container pressure shall be marked “LP-Gas” or “LPG” at not greater than 10-foot intervals.
(iii)
Hose subject to container pressure shall be designed for a bursting pressure of not less than 1,250 p.s.i.g.
(iv)
Hose subject to container pressure shall have its correctness as to design construction and performance determined by being listed (see § 1910.110(a)(15) ).
(v)
Hose connections subject to container pressure shall be capable of withstanding, without leakage, a test pressure of not less than 500 p.s.i.g.
(vi)
Hose and hose connections on the low-pressure side of the regulator or reducing valve shall be designed for a bursting pressure of not less than 125 p.s.i.g. or five times the set pressure of the relief devices protecting that portion of the system, whichever is higher.
(vii)
Hose may be used on the low-pressure side of regulators to connect to other than domestic and commercial gas appliances under the following conditions:
(a) The appliances connected with hose shall be portable and need a flexible connection.
(b) For use inside buildings the hose shall be of minimum practical length, but shall not exceed 6 feet except as provided in paragraph (c)(5)(i)(g) of this section and shall not extend from one room to another, nor pass through any walls, partitions, ceilings, or floors. Such hose shall not be concealed from view or used in a concealed location. For use outside of buildings, the hose may exceed this length but shall be kept as short as practical.
(c) The hose shall be approved and shall not be used where it is likely to be subjected to temperatures above 125 °F. The hose shall be securely connected to the appliance and the use of rubber slip ends shall not be permitted.
(d) The shutoff valve for an appliance connected by hose shall be in the metal pipe or tubing and not at the appliance end of the hose. When shutoff valves are installed close to each other, precautions shall be taken to prevent operation of the wrong valve.
(e) Hose used for connecting to wall outlets shall be protected from physical damage.
(10) Safety devices.
(i)
Every container except those constructed in accordance with DOT specifications and every vaporizer (except motor fuel vaporizers and except vaporizers described in paragraph (b)(11)(ii)(c) of this section and paragraph (d)(4)(v)(a) of this section) whether heated by artificial means or not, shall be provided with one or more safety relief valves of spring-loaded or equivalent type. These valves shall be arranged to afford free vent to the outer air with discharge not less than 5 feet horizontally away from any opening into the building which is below such discharge. The rate of discharge shall be in accordance with the requirements of paragraph (b)(10)(ii) or (b)(10)(iii) of this section in the case of vaporizers.
(ii)
Minimum required rate of discharge in cubic feet per minute of air at 120 percent of the maximum permitted start to discharge pressure for safety relief valves to be used on containers other than those constructed in accordance with DOT specification shall be as follows:
| Surface area (sq. ft.) | Flow rate CFM air |
|---|---|
| 20 or less | 626 |
| 25 | 751 |
| 30 | 872 |
| 35 | 990 |
| 40 | 1,100 |
| 45 | 1,220 |
| 50 | 1,330 |
| 55 | 1,430 |
| 60 | 1,540 |
| 65 | 1,640 |
| 70 | 1,750 |
| 75 | 1,850 |
| 80 | 1,950 |
| 85 | 2,050 |
| 90 | 2,150 |
| 95 | 2,240 |
| 100 | 2,340 |
| 105 | 2,440 |
| 110 | 2,530 |
| 115 | 2,630 |
| 120 | 2,720 |
| 125 | 2,810 |
| 130 | 2,900 |
| 135 | 2,990 |
| 140 | 3,080 |
| 145 | 3,170 |
| 150 | 3,260 |
| 155 | 3,350 |
| 160 | 3,440 |
| 165 | 3,530 |
| 170 | 3,620 |
| 175 | 3,700 |
| 180 | 3,790 |
| 185 | 3,880 |
| 190 | 3,960 |
| 195 | 4,050 |
| 200 | 4,130 |
| 210 | 4,300 |
| 220 | 4,470 |
| 230 | 4,630 |
| 240 | 4,800 |
| 250 | 4,960 |
| 260 | 5,130 |
| 270 | 5,290 |
| 280 | 5,450 |
| 290 | 5,610 |
| 300 | 5,760 |
| 310 | 5,920 |
| 320 | 6,080 |
| 330 | 6,230 |
| 340 | 6,390 |
| 350 | 6,540 |
| 360 | 6,690 |
| 370 | 6,840 |
| 380 | 7,000 |
| 390 | 7,150 |
| 400 | 7,300 |
| 450 | 8,040 |
| 500 | 8,760 |
| 550 | 9,470 |
| 600 | 10,170 |
| 650 | 10,860 |
| 700 | 11,550 |
| 750 | 12,220 |
| 800 | 12,880 |
| 850 | 13,540 |
| 900 | 14,190 |
| 950 | 14,830 |
| 1,000 | 15,470 |
| 1,050 | 16,100 |
| 1,100 | 16,720 |
| 1,150 | 17,350 |
| 1,200 | 17,960 |
| 1,250 | 18,570 |
| 1,300 | 19,180 |
| 1,350 | 19,780 |
| 1,400 | 20,380 |
| 1,450 | 20,980 |
| 1,500 | 21,570 |
| 1,550 | 22,160 |
| 1,600 | 22,740 |
| 1,650 | 23,320 |
| 1,700 | 23,900 |
| 1,750 | 24,470 |
| 1,800 | 25,050 |
| 1,850 | 25,620 |
| 1,900 | 26,180 |
| 1,950 | 26,750 |
| 2,000 | 27,310 |
Surface area=total outside surface area of container in square feet.
When the surface area is not stamped on the nameplate or when the marking is not legible, the area can be calculated by using one of the following formulas:
(1) Cylindrical container with hemispherical heads:
Area=Overall length×outside diameter× 3.1416.
(2) Cylindrical container with other than hemispherical heads:
Area=(Overall length 0.3 outside diameter) ×outside diameter×3.1416.
(3) Spherical container:
Area=Outside diameter squared×3.1416.
Flow Rate-CFM Air=Required flow capacity in cubic feet per minute of air at standard conditions, 60 F. and atmospheric pressure (14.7 p.s.i.a.).
The rate of discharge may be interpolated for intermediate values of surface area. For containers with total outside surface area greater than 2,000 square feet, the required flow rate can be calculated using the formula, Flow Rate-CFM Air=53.632 A0.82.
A=total outside surface area of the container in square feet.
Valves not marked “Air” have flow rate marking in cubic feet per minute of liquefied petroleum gas. These can be converted to ratings in cubic feet per minute of air by multiplying the liquefied petroleum gas ratings by factors listed below. Air flow ratings can be converted to ratings in cubic feet per minute of liquefied petroleum gas by dividing the air ratings by the factors listed below.
| Container type | 100 | 125 | 150 | 175 | 200 |
| Air conversion factor | 1.162 | 1.142 | 1.113 | 1.078 | 1.010 |
(iii)
Minimum Required Rate of Discharge for Safety Relief Valves for Liquefied Petroleum Gas Vaporizers (Steam Heated, Water Heated, and Direct Fired).
The minimum required rate of discharge for safety relief valves shall be determined as follows:
(a) Obtain the total surface area by adding the surface area of vaporizer shell in square feet directly in contact with LP-Gas and the heat exchanged surface area in square feet directly in contact with LP-Gas.
(b) Obtain the minimum required rate of discharge in cubic feet of air per minute, at 60 °F. and 14.7 p.s.i.a. from paragraph (b)(10)(ii) of this section, for this total surface area.
(iv)
Container and vaporizer safety relief valves shall be set to start-to-discharge, with relation to the design pressure of the container, in accordance with Table H-26.
(v)
Safety relief devices used with systems employing containers other than those constructed according to DOT specifications shall be so constructed as to discharge at not less than the rates shown in paragraph (b)(10)(ii) of this section, before the pressure is in excess of 120 percent of the maximum (not including the 10 percent referred to in paragraph (b)(10)(iv) of this section) permitted start to discharge pressure setting of the device.
| Containers | Minimum (percent) | Maximum (percent) |
|---|---|---|
| ASME Code; Par. U-68, U-69—1949 and earlier editions | 110 | 1 25 |
| ASME Code; Par. U-200, U-201—1949 edition | 88 | 1 100 |
| ASME Code—1950, 1952, 1956, 1959, 1962, 1965 and 1968 (Division I) editions | 88 | 1 100 |
| API—ASME Code—all editions | 88 |
|