Current through Register Vol. 18, September 20, 2024
(1)
Design, working pressure and classification of containers:
(a) containers shall be constructed in
accordance with ARM
4.12.704 with a minimum design
pressure of 250 psig;
(b) U-68 and
U-69 ASME Code containers with a design pressure of 200 psig are acceptable if
recertified to 250 psig and equipped with safety relief valves set at 250 psig
as stated in ARM
4.12.710(2).
(2) Installation of storage
containers:
(a) Aboveground installation of
anhydrous ammonia containers shall be installed on reinforced concrete footings
or foundations or structural steel supports mounted on reinforced concrete
foundations or sufficient equivalent prepared on gravel pad. The reinforced
concrete foundations or footings must extend below the established frost line
and shall be of sufficient width and thickness to support the total weight of
the containers and contents adequately. The foundations shall maintain the
lowest point of the tank at not less than 24 inches above the ground. I-beams
shall support the weight of the tank and product.
(b) Skid-mounted anhydrous ammonia storage
tanks must be installed on permanent concrete footing or adequate floating
reinforced concrete slabs. Skid-mounted units shall include all piping and
pumps or compressors as one unit. If the design of such a unit precludes a
minimum of 24 inches ground-to-tank clearance, bottom-side inlet, outlet valves
and piping are prohibited.
(c)
Horizontal aboveground containers shall be mounted on foundations in such a
manner as to permit expansion and contraction. Every container shall be
supported so as to prevent the concentration of excessive loads on the
supporting portion of the shell. Means of preventing corrosion shall be
provided on that portion of the container in contact with the foundations or
saddles.
(d) Secure anchorage or
adequate pier height shall be provided against container flotation wherever
high flood water might occur.
(e)
Distance between aboveground containers over 2000 gallons capacity shall be at
least five feet.
(f) Container
buried underground shall be placed so that the top of the container is at least
one foot below the surface of the ground. Should ground conditions make
compliance with this requirement impracticable, precautions, such as guard
rails, shall be taken to prevent physical damage to the container. It will not
be necessary to cover the portion of the container to which a manhole and other
connections are affixed. When necessary to prevent flotation, containers shall
be securely anchored or weighted.
(g) Underground containers shall be set on
firm foundations (firm earth may be used) and surrounded with soft earth or
sand well tamped in place. As a further means of resisting corrosion, the
container, prior to being placed underground, shall be given a protective
coating equivalent to hot dip galvanizing or two preliminary coatings of red
lead followed by a heavy coating of coal tar or asphalt. The coated container
shall be lowered into place in such a manner as to prevent abrasion or other
damage to the coating.
(3) Container valves and accessories:
(a) all containers shall be equipped with a
fixed liquid level gauge;
(b) all
containers shall be equipped with a vapor pressure indicating gauge having a
dial graduated from 0-400 psig;
(c)
the filling connection shall be fitted with an approved combination
back-pressure check valve, excess-flow valve, or a positive shutoff valve in
conjunction with either an internal back-pressure check valve or an internal
excess-flow valve;
(d) all
containers shall be equipped with an approved vapor return valve;
(e) all vapor and liquid connections, except
safety relief valves and those specifically exempt in this section, shall be
equipped with approved excess-flow valves or fitted with approved remote
controlled quick-closing internal valves which shall remain closed, except
during operating periods.
(4) Every container shall be provided with
one or more safety relief valves of the spring-loaded type and shall comply
with the following:
(a) The discharge from
safety relief valves shall be directed upward, unobstructed into the open air,
and away from the container. Vent pipes shall not be restricted nor smaller in
size than the relief valve outlet connection. All relief valve discharges shall
have raincaps that will allow the free discharge of the vapor and prevent the
entrance of water. Provision shall be made for draining condensation which may
accumulate.
(b) Vent pipes from two
or more safety relief devices located on the same unit or similar lines from
two or more different units may be run into a common header, provided the
cross-sectional area of the header is at least equal to the sum of the
cross-sectional area of the individual vent pipes.
(5) Underground containers:
(a) Spring-loaded relief valves installed on
underground containers may be reduced to a minimum of 30 percent of the rate of
discharge specified in Table A. Containers so protected shall not be uncovered
after installation until the liquid anhydrous ammonia has been removed.
Containers which may contain liquid anhydrous ammonia before being installed
underground and before completely covered with earth are to be considered
aboveground containers when determining the rate of discharge requirement of
the relief valves.
(b) The
discharge from vent pipes should be above the possible water level on
underground installation where there is a probability that the manhole or
housing may become flooded. All manholes or housings shall be provided with
ventilated louvers or their equivalent. The area of such openings shall equal
or exceed the combined discharge areas of safety relief valves and vent pipes
that discharge their content into the manhole housing.
(6) Each tank or group of tanks shall be
marked on at least two approaching sides with the words "Caution-Ammonia" or
"Caution-Anhydrous Ammonia" in sharply contrasting colors with letters not less
than four inches high.
(7)
Individual storage container capacity shall be limited only by good engineering
practice (according to the code).
(8) Protection of tank accessories and
grounding:
(a) Valves and other appurtenances
shall be protected against tampering and physical damage. Such appurtenances
shall also be protected during the transit of containers intended for
installation underground.
(b) All
connections to underground containers shall be located within a metal dome,
housing, or manhole fitted with a metal removable cover.
(c) Storage tanks need not be grounded. Where
an electrical system exists, such as for lights or pump motors, the electrical
system shall be installed and grounded in a manner as required by the National
Electrical Code or local ordinance.
(d) Manually controlled valves, which if open
would allow anhydrous ammonia to discharge into the atmosphere, shall be kept
secured when the installation is unattended.
(e) All areas occupied by storage
installations shall be kept free of dry grass and weeds.
(f) The owner of an abandoned storage system
shall be responsible for its maintenance, safe disposal of anhydrous ammonia,
and shall keep the storage site free of dry grass and weeds.
(9) Containers once installed
underground shall not later be installed aboveground or underground, unless
they successfully withstand hydrostatic pressure tests at the pressure
specified for the original hydrostatic test as required by the code under which
the container was constructed and show no evidence of serious corrosion.
Reinstalled containers must also comply with ARM
4.12.719(3).