My previous article on the Anhydrous Ammonia requirements generated a lot of questions, mostly about how OSHA worded their requirements when it came to Excess Flow Valves, Check Valves, Unloading, and Emergency Shutoff Valves.  So this posting I used one of my favorite sources, WA States LNI standards, to present the material in a more straight forward manner.  I am just covering the non-refrigerated tanks and the operational designs in this article.

You must locate Anhydrous Ammonia containers either:

1. In buildings or parts of the building provided for ammonia storage; or
2. Outside, away from densely populated

You must locate containers according to Table 1, Minimum Distances for Container

Table 1 – Minimum Distances for Container Location
	Minimum Distances (feet) from Container to:
Nominal Capacity of Container	Line of Adjoining Property Which may be built upon, Highways & Mainline of Railroad	Place of Public Assembly	Institution Occupancy
Over 500 to 2,000	25	150	250
Over 2,000 to 30,000	50	300	500
Over 30,000 to 100,000	50	450	750
Over 100,000	50	600	1,000

 

You must make sure containers are located to meet all of the following:

1. Away from readily ignitable materials such as weeds, long dry grass, and
2. So there is no adverse impact on employee health through unnecessary exposure
3. At least fifty feet away from dug wells and other sources of potable water
   1. EXCEPTION: If the container is a part of a water treatment installation, this requirement does not apply.
4. You must maintain legibility of all container and valve markings

 

Construct and test containers according to the Unfired Pressure Vessel Code (ASME Section VIII].

Make sure the minimum design pressure of the container is 250 psig.

Make sure all containers with a capacity exceeding two hundred fifty (250) gallons are constructed to meet one or more of the following:

(a) Stress relieved after fabrication according to the Unfired Pressure Vessel Code;

(b) Have stress relieved cold-formed heads;

(c) Hot-formed heads

 

Installation

Provide a minimum distance of five (5) feet between aboveground and underground containers that have more than a twelve-hundred (1,200) gallon capacity each.

 

Protect containers from floating away, in areas with a potential for high floodwaters, by providing either:

1. Secure anchorage; or
2. Adequate pier

Follow Table 2 for the aboveground, NONREFRIGERATED containers.

 

Table 2 – ABOVEGROUND NONREFRIGERATED CONTAINER Requirements
If you have:	Then:
Aboveground containers	Provide one of the following:
	1.	Substantial reinforced concrete footings and foundations; or
	2.	Structural steel supports mounted on reinforced concrete foundations.
	Make sure the reinforced concrete foundation meets all of the following:
	1.	Extends below the established frost line.
	2.	Is of sufficient width and thickness to support the total weight of the containers and contents.
	3.	Has the lowest point of the tank at least 18 inches above the ground.
	Make sure the footings meet all of the following:

	1.	Extend below the established frost line.
	2.	Are of sufficient width and thickness to support the total weight of the containers and contents.
Floating type foundations on containers installed aboveground	Make sure they are designed to adequately support the tank, contents, and pumping equipment.
A horizontal, aboveground container	Mount the container on a foundation that permits expansion and contraction.
	Prevent the weight of excessive loads from resting on the supporting portion of the shell.
	Provide saddle bearing that extends over at least 1/3 the circumference of the shell.
	Prevent corrosion on the portions of the container in contact with the foundations or saddles.

 

Hose specifications

Make sure hose used in ammonia service and subject to container pressure meets both of the following:

• The Joint Rubber Manufacturers Association, RMA-IP-14, Specifications for Anhydrous Ammonia Hose 7th Edition 2003; and
• The Fertilizer Institute’s Hose Specifications for Anhydrous Ammonia.

Hose assemblies are able to withstand a 500 psig pressure test

Follow Table 4 for hose specifications

 

Table 4 – Hose Specifications
If you have:	Then:
Hose subject to container pressure	Design it with a minimum working pressure of 350 psig; and
	Burst pressure of 1750 psig.
Hose and their connections	Design them for the maximum low side working pressure when located on either:
	1.	The pressure reducing valves on devices discharging to atmospheric pressure; or
	2.	The low pressure side of flow control.
	Design, construct, and install so there is no leakage when connected.
Liquid transfer hose that is not drained of liquid upon completion of transfer operations	Equip with an approved shut off valve at the discharge end.
	Prevent excessive hydrostatic pressure in the hose.
Hose with an outside diameter one-half inch and larger	Make sure the hose is marked and legible at 5-foot intervals.

 

PIPING, TUBING, AND FITTINGS

PROHIBIT the use of cast iron

The use of malleable or nodular iron such as Specification ASTM A47 or ASTM A395 is permitted.

Make sure all metal flexible connections for permanent installations have a minimum working pressure of 250 psig

Make sure all pipes, tubes, and fittings used for ammonia service meet all of the following:

• Made of material with a design pressure at least equal to the maximum service
• Well supported and have provisions for all of the following:
  • Expansion;
  • Contraction;
  • Vibration;
  • Jarring;

Protect all exposed pipes from damage resulting from undue strain including:

• Moving machinery;
• The presence of vehicles

Use ammonia resistant joint compounds

Make sure, after assembly, that all piping and tubing are leak-free at a pressure not less than the normal operating pressure of the system.

 

Nonrefrigerated systems

Make sure piping on nonrefrigerated systems is:

• ASTM A-53-2004 Electrical  Resistance  Welded  and Electric Flash Welded Pipe or equal
• At least schedule 80 when joints are threaded
• At least schedule 40 when joints are either welded or welded and flanges

Prohibit the use of piping or tubing made of any of the following:

• Brass;
• Copper;
• Galvanized steel

 

Appurtenance requirements for ALL systems

Make sure each appurtenance installed BEFORE February 8, 1973, is determined to be safe by meeting one of the following:

• Approved, tested, and installed by either:

• • The American National Standard for the Storage and Handling of Anhydrous Ammonia (in effect at the time of installation);
  • The Fertilizer Institute Standards for the Storage and Handling of Agricultural Anhydrous Ammonia (in effect at the time of installation).

• Accepted, certified, listed, or labeled, by a nationally recognized testing laboratory
• Inspected or tested by a federal, state, municipal, or local authority responsible for enforcing occupational safety provisions, when no nationally recognized laboratory will provide
• Tested and approved by a registered professional engineer or other qualified people if the system is a custom-designed or custom-built unit and no other recognized entity will provide approval
• Keep a document on file signed by the qualified person that indicates the unit is safe. Include the test bases, test data, and results and the qualifications of the qualified person.

Make sure container appurtenances are both of the following:

1. Designed for at least the working pressure for the portion of the system where installed; and
2. Fabricated from materials suitable for anhydrous ammonia service

Make sure fixed liquid level gauges:

1. Are designed so the maximum volume of the container filled by liquid does not exceed eighty-five percent (85%) of its water capacity; and
2. Have a coupling into which it is threaded that is placed at the eighty-five percent (85%) level of the container

If located elsewhere, install the dip tube of this gauge so it can not be easily removed.

Equip each container, except those filled by weight, with an approved liquid level gauging device that does ALL of the following:

1. Has a design pressure equal to or greater than the design pressure of the container;
2. Is arranged so the maximum liquid fill level of containers can be readily determined

Follow additional requirements found in Table 5, Appurtenance Requirements for all Systems

Table 5 – Appurtenance Requirements for all Systems
If you have:	Then make sure they:
Safety relief devices	Do not have discharge termination in or beneath any building.
Safety relief valves	Have a flow capacity that is not restricted by any connection to it on either the upstream or downstream side.
Connections to containers	Have shut off valves located as close to the container as possible.
	Exemption: Safety relief devices, gauging devices, or devices fitted with a No. 54 drill size holes are not required to have shut off valves located as close to the container as possible.
Connections and the line, including valves and fittings	Have a greater rated flow than the excess flow valves that protects them.
Excess flow valves, where required	Meet all of the following:
	1.	Are designed with a bypass no larger than a No. 60 drill size opening to allow equalization of pressures.

	2.	Close automatically at the rated flow of vapor or liquid specified by the manufacturer.
	3.	Maintain legible markings.
Excess flow valves provided with shut off valves	Are designed to close if the shut-off valve breaks during installation.
Excess flow and back pressure check valves, where required	Are located either:
	1.	Inside the container; or
	2.	Outside the container as long as the excess flow valve is:
	a.	As close as possible to the entrance of the line; and
	b.	Installed without excessive stress that could result in breakage between the container and the valve.
Liquid level gauging devices that:	Are either:
Require bleeding of the product into the atmosphere such as the rotary tube, fixed tube, and slip tube devices	1.	Designed so that the maximum opening of the bleed valve is not larger than No. 54 drill size; or
	2.	Provided with an excess flow valve.
	Exemption:
	1.	If openings from the containers or through fittings are attached directly onto the container where pressure gauge connections are made, then there is no need for excess flow valves as long as the openings are not larger than a No. 54 drill size.
	2.	This requirement does not apply to farm vehicles used for the application of ammonia as covered by WAC 296-826-50030.

 

Follow Table 6, Safety Valve Start to Discharge Rate, and Table 7, Safety Relief Valve Rate of Discharge, for the following systems:

• Nonrefrigerated stationary containers;
• Mounted on trucks, semi-trailers, and trailers used for the transportation of ammonia;
• Mounted on farm wagons for the transportation of ammonia;
• Mounted on farm equipment for the application of

EXEMPTION:

The rate of discharge of spring-loaded safety relief valves installed on underground containers may be reduced to thirty percent of the rate of discharge specified in Table 6, Safety Relief Valve Rate of Discharge so long as the container is not uncovered after installation until the liquid ammonia has been removed.

 

Table 6 – Safety Valve Start to Discharge Rate
Containers	Minimum	Maximum*
ASME U-68, U-69	110%	125%
ASME U-200, U-201	95%	100%
ASME 1952, 1956, 1959, 1962, 1965, 1968, or 1971	95%	100%
API-ASME	95%	100%
U.S. Coast Guard	(As required by U.S.C.G. regulations)
DOT	(As required by DOT regulations)

Note: A relief valve manufacturer’s tolerance of plus ten percent is permitted.

Instructions are found below the table

 

Table 7 – Safety Relief Valve Rate of Discharge
Surface Area sq. ft.	Flow Rate CFM Air	Surface Area sq. ft.	Flow Rate CFM Air	Surface Area sq. ft.	Flow Rate CFM Air	Surface Area sq. ft.	Flow Rate CFM Air
20	258	145	1,310	340	2,640	1,350	8,160
25	310	150	1,350	350	2,700	1,400	8,410
30	360	155	1,390	360	2,760	1,450	8,650
35	408	160	1,420	370	2,830	1,500	8,900
40	455	165	1,460	380	2,890	1,550	9,140
45	501	170	1,500	390	2,950	1,600	9,380
50	547	175	1,530	400	3,010	1,650	9,620
55	310	180	1,570	450	3,320	1,700	9,860
60	360	185	1,600	500	3,620	1,750	10,090
65	408	190	1,640	550	3,910	1,800	10,330
70	455	195	1,670	600	4,200	1,850	10,560
75	762	200	1,710	650	4,480	1,900	10,800
80	804	210	1,780	700	4,760	1,950	11,030
85	845	220	1,850	750	5,040	2,000	11,260
90	885	230	1,920	800	5,300	2,050	11,490
95	925	240	1,980	850	5,590	2,100	11,720
100	965	250	2,050	900	5,850	2,150	11,950
105	1,010	260	2,120	950	6,120	2,200	12,180
110	1,050	270	2,180	1,000	6,380	2,250	12,400
115	1,090	280	2,250	1,050	6,640	2,300	12,630
120	1,120	290	2,320	1,100	6,900	2,350	12,850
125	1,160	300	2,380	1,150	7,160	2,400	13,080
130	1,200	310	2,450	1,200	7,410	2,450	13,300
135	1,240	320	2,510	1,250	7,660	2,500	13,520
140	1,280	330	2.570	1,300	7,910

 

Table instructions:

• The surface area = the total outside surface area of the container in square
• When the surface area is not stamped on the nameplate or the marking is not legible, calculate the area by using Table 8, Surface Area

Table 8 Surface Area
If you have:	Then calculate as follows:
Cylindrical container with hemispherical heads	Area = overall length in feet times the outside diameter in feet times 3.1416
Cylindrical container with other than hemispherical heads	Area = (overall length in feet plus 0.3 outside diameter in feet) times outside diameter in feet times 3.1416
Spherical container	Area = outside diameter in feet squared times 3.1416

 

Flow rate: CFM air = cubic feet per minute of air required at standard conditions, 60°F, and atmospheric pressure (14.7 psia).

• The rate of discharge may be altered for intermediate values of surface
• For containers with total outside surface area greater than 2,500 sq. ft., the required flow rate can be calculated using the formula, flow rate CFM air = 22.11 A0.82 where A = outside surface area of the container in square

 

Nonrefrigerated stationary containers

Important:

In addition to this section, you need to follow the Appurtenances requirements above

 

All containers are to be equipped with all of the following:

• An approved vapor return valve;
• A fixed maximum liquid level gauge;
• A pressure gauge that is both:
  • Graduated from zero to 400 psig; and
  • Designed for use in ammonia

Provide one or more spring-loaded safety relief valves, or an equivalent type, on all containers

Make sure safety relief valves do ALL of the following:

• Discharge in the following ways:
  • Away from the container in an upward, unobstructed manner in- to the atmosphere;
  • Not in or beneath a building
• Have rain caps that allow free discharge of the vapor and prevent the entrance of water;
• Have a method for draining accumulated condensation;
• Have a start to discharge, related to the design pressure of the container, according to Table 6, Safety Valve Start to Discharge Rate;
• Are arranged to minimize the possibility of tampering;
• Are provided, when the pressure setting adjustment is external, with a means of sealing the adjustment;
• Have direct communication with the vapor space of the container.

Note:

Vent pipes from 2 or more safety relief devices located on the same unit, or similar lines from 2 or more different units, may be run into a common header if the cross-sectional area of the header is at least equal to the sum of the cross-sectional areas of the individual vent pipes.

 

Protect container appurtenances against physical damage and during transit of containers intended for underground installation.

Make sure shut off valves are not installed between the safety relief valve and the container or system. A shut off valve may be used if arranged so that the required capacity flow is maintained.

EXEMPTION:	You are exempt from the requirement not to install the shut off valve between the safety relief valve and the container or systems in the following situations:
	1. A three-way valve installed under two safety relief valves, each with:
	a. The required rate of discharge; and
	b. Installed to allow either of the safety relief valves to be closed off but not at the same time.
	2. Two separate relief valves are installed with individual shut off valves.
	3. The two shut off valve stems must be mechanically interconnected to allow the full required flow of one safety relief valve at all times.
	4. When a safety relief valve manifold that allows:
	a. One valve of two or more to be closed off; and
	b. The remaining valve or valves will provide not less than the rate of discharge shown on the manifold nameplate.

 

Make sure vapor and liquid connections have either of the following:

• An approved excess flow valve; or
• An approved quick-closing internal valve that remains closed except during operations

EXEMPTION:	The following do not need to be fitted with excess flow valves:
	1. Safety relief valves.
	2. Liquid level gauging devices that require both of the following:
	a. Bleeding of the product into the atmosphere;
	b. Construction so that outward flow will not exceed that passed by a No. 54 drill size opening.
	Those with openings from the containers or through fittings that are attached directly onto the container where pressure gauge connections are made as long as: The openings are not larger than a No. 54 drill size.

 

Follow additional requirements found in Table 9, Appurtenances for Nonrefrigerated Stationary

 

 

Table 9 – Appurtenances for Nonrefrigerated Stationary Containers
If you have:	Then make sure they:
Columnar-type gauges	1.	Are restricted to stationary storage installations.
	2.	Are shielded against the direct rays of the sun.
	3.	Are equipped with all of the following:
	a.	Shut off valves having metallic hand-wheels;

	b.	Excess flow valves;
	c.	Extra heavy glass that is adequately protected with a metal housing applied by the gauge manufacturer.
Main shut off valves	Are kept closed and locked when the installation is unattended.
	Exemption: Valve locks are not required if the facility is protected against tampering by fencing or other suitable means.
Filling connections	Are provided with one of the following:
	1.	Combination back-pressure check valve and excess flow valve.
	2.	One double or two single back-pressure check valves.
	3.	A positive shut off valve in conjunction with either an internal back-pressure check valve or an internal excess flow valve.
Underground installations with a probability of the manhole or housing becoming flooded	1.	Have vent lines located above the high water level.
	2.	Have manholes or housings with ventilated louvers or their equivalent with the area of their openings equal or exceeding the combined discharge areas of the safety relief valves and vent lines which discharge their content into the manhole housing.
Hydrostatic relief valves	Are installed between each pair of valves in the liquid ammonia piping or hose.

 

 

TRANSFERRING LIQUIDS

Make sure transfer containers are gauged and filled in either:

1. Open atmospheres; or
2. Buildings approved for that purpose

Make sure pumps used to transfer ammonia meet all of the following:

1. Have a manufacturer’s label for ammonia
2. Are designed for at least 250 psig working
3. Have a constant differential relief valve discharging into the suction port that:
   1. Is installed on positive displacement pumps; and
   2. Meets the pump manufacturer’s recommendation for the settings and installation
4. Have a pressure gauge graduated zero to 400 psig installed on the discharge side before the relief valve

Make sure plant pipes with shut off valves are located as close as possible to the pump

Make sure meters used for measuring liquid anhydrous ammonia:

1. Are recommended and labeled for ammonia service by the manufacturer.
2. Are designed for a minimum working pressure of 250

Incorporate devices that prevent unintended measurement of vapor.

You must do the following when transferring ammonia:

1. Maintain ammonia at a temperature suitable for the receiving container.
2. Have at least one attendant supervise the transfer from the time connections are made to when disconnection
3. Do NOT use flammable gases or gases that will react with ammonia, such as air to unload tank cars or transport

Make sure compressors used for transferring ammonia meet all of the following:

1. Have a working pressure of at least 250 psig when transferring ammonia
   1. If crankcases of compressors are not designed to withstand system pressure, then provide protection with a suitable safety relief valve.
2. Are connected to plant piping with shut off valves located as close as practical to the compressor
3. Have a safety relief valve that is both:
   1. Large enough to discharge the full capacity of the compressor; and
   2. Connected to the discharge before any shutoff valve
4. Have an oil separator on the discharge side, where necessary to prevent contamination
5. Have a drainable liquid trap or other adequate methods on the compressor suction to minimize the entry of liquids into the compressor.
6. Pressure gauges on the suction and discharge end graduated to at least one and one-half times the maximum pressure that can develop.

Protect loading and unloading systems in the event of hose severance by suitable devices where necessary, such as:

1. Backflow check valves; or
2. Properly sized excess flow

Note:

If such valves are not practical, remotely operated shut off valves may be installed.