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AMERICAN NATIONAL STANDARD K61.1-1991 may be run into a common header, provided the ground conditions make compliance with these cross-sectional area of such header is at least equal to the sum of the cross-sectional areas of he be taken eto sp event physicaPracticable rdamage to the individual vent pipes. container.It is not necessary to cover the portion -3.3.2 The rate of discharge of spring-loaded of the container to which a manhole and other pressure relief valves installed on underground connections are affixed. When necessary to prevent floating, containers shall be securely containers may be reduced to a minimum of 30 Per cent of the rate of discharge specified in anchored or weighted. Appendix A.Containers so protected shall not be 3.4.4 Underground containers shall be set on uncovered after installation until the liquid firm foundations (firm earth may be used) and ammonia has been removed. Containers which surrounded with soft earth or sand well tamped may contain liquid ammonia before being in- in place. As a further means of resisting corro- stalled underground and before beingcompletely sion, the container, prior to being placed under- covered with earth are to be considered above- ground, shall be given a protective coating ground containers when determining the rate of satisfactory to the authority having jurisdiction. discharge requirements of the pressure relief Such protective coatingshall be equivalentto hot valves. dip galvanizing,or to two preliminary coatings of red lead followed by a heavy 3.3.3 On underground installations where there is a probability of the manhole or housing asphalt. The container thus coated shall lowered into place in such a manner be prevent abrasion or other damage to the coating becoming flooded, the discharge from vent lines tg. prevent shall be located above the high water level. All manholes or housings shall be provided with 3.4.5 Distance between aboveground and ventilated louvres or their equivalent,the area of underground containers of over 1,200 gallons such openings equalling or exceeding combined (4.54 m3)capacity shall be at least five ft.(1.5 m). discharge areas of pressure relief valves and vent lines which discharge their content into the manhole housing. 3.4.6 Secure anchorage or adequate pier OILheight shall be provided against container 3.4 Installation of Storage Containers flotation wherever sufficiently high flood water might o^-cur. 3.4.1 Containers installed aboveground shall be provided with substantial reinforced concrete 3.5 Reinstallation of Containers footings and foundations or structural steel supports mounted on reinforced concrete founda- 3.5.1 Containers once installed underground tions. In either case, the reinforced concrete shall not later be reinstalled aboveground or foundations or footings shall extend below the underground,unless they successfully withstand established frost line and shall be of sufficient hydrostatic pressure retests at the pressure width and thickness to support the total weight of specified for the original hydrostatic test as the containers and contents adequately. The required by the code under which the tank was foundation shall maintain the lowest point of the constructed and show no evidence of serious tank at not less than 18 inches(457 mm)above the corrosion. ground. Floating type foundations shall also be 3.5.2 Where containers are reinstalled under- acceptable providing the foundations are de- ground, the corrosion resistant coating shall be signed to adequately support the tank, contents put in good condition;see 3.4.4.Where containers and pumping equipment. (See Section 2.7) are reinstalled aboveground, pressure relief 3.4.2 Horizontal aboveground containers shall devices or gaging devices shall comply with 2.9 be mounted on foundations in such a manner as to and 3.3 respectively for aboveground containers. permit expansion and contraction. Every con- 3.6 Markin tamer shall be supported so as to prevent the g of Containers concentration of excessive loads on the supporting 3.6.1 Each container or group of containers portion of the shell. The bearing afforded by the shall be marked on at least two sides with the saddles shall extend over at least one third of the words "Anhydrous Ammonia' or "Caution— circumference of the shell. Suitable means for Ammonia" in sharply contrasting colors with preventing corrosion shall be provided on that letters not less than four inches high. portion of the container in contact with the foundations or saddles. 3.7 Protection of Container Appurtenances 3.4.3 Containers buried underground shall be 3.7.1 Valves and other appurtenances shall be placed so that the top of the container is at least protected against physical damage. Main Ion- one foot below the surface of the ground. Should tainer shut-off valves shall be kept closed and 17