Ohio State University Fact Sheet

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Safe Handling of Anhydrous Ammonia

AEX-594

Timothy J. Lawrence
Dr. Thomas G. Carpenter
Dr. Thomas L. Bean

Farmers throughout Ohio use anhydrous ammonia (NH³) as one source of nitrogen fertilizer for crops. All associated personnel should be familiar with the safe use of anhydrous ammonia, understand the potential for injury and know how to respond to an emergency. Anhydrous ammonia is caustic and will cause severe bums to the eyes, skin and respiratory tract. Anhydrous ammonia is a strong alkali that can cause death or severe injury to body tissue due to its caustic, corrosive, freezing and dehydrating action. Its strong affinity for water and rapid evaporation creates an almost instant freeze-drying process when the liquid NH³ comes in contact with body tissue.

Stored as a liquid under pressure, NH³ vaporizes to a colorless gas at atmospheric pressure and a temperature of -28 degrees F. It is important to understand that vapor pressure of NH³ will increase as the temperature increases. The pressure relief valve on the tanks are set to open at 250 psig. This pressure will be reached if the tank temperature reaches 116 degrees F (see graph below). Conditions that permit tank temperatures to increase drastically (i.e., left in the direct sunlight during very hot days) should be avoided.

As temperature increases, the vapor pressure of the anhydrous ammonia in the nurse tank increases. At 116 degrees F the pressure in the tank will reach 250 psig and anhydrous ammonia will be released.

Ammonia dissolved in water will react readily with copper, zinc, brass and many alloys. Only non-galvanized steel or iron should be used for containers, fittings and piping (Schedule 80 pipe or Schedule 40 when welded by a certified welder). All materials used with anhydrous ammonia should conform to recommended standards. Anhydrous ammonia tanks should not be used to store other materials such as propane or liquefied petroleum gas.

Accident Situations

The accidental release of anhydrous ammonia can create a dangerous situation for both the handler and bystanders. The following situations are dangerous:

• Overfilling the tank.
• Handling the hose by the valve handle or hand wheel.
• Faulty hitch pin or weakened tongue.
• Weakened undercarriage structure.
• Moving the tank before disconnecting the hose.
• Faulty valves and deteriorated or out-of-date hoses.
• Not using personal protective equipment.
• Failure to bleed pressurized NH³ from the hose before connecting or disconnecting.
• Failure to have sufficient amounts of water available.
• Overturning an applicator tank.
• External overheating of the storage container.

An estimated eighty percent of reported accidents result from improper procedure, lack of knowledge or training, and failure to follow proper safety precautions. Accidents can be reduced if all individuals follow safety rules and maintain the equipment properly. It is essential that all equipment be in good operating condition. Only trained individuals should handle and apply anhydrous ammonia.

Personal Protection

Goggles, rubber gloves, and complete protective clothing are necessary when handling anhydrous ammonia. It is recommended that goggles and a face shield or an approved respirator be used to protect the eyes and face from a direct blast of ammonia that can permanently blind and disfigure an individual.

Water must be available for flushing the eyes and skin in case of exposure. Each vehicle used for anhydrous ammonia must carry a five-gallon container of clean water. Anyone handling NH³ should carry a six to eight-ounce squeeze bottle of water in their shirt pocket for rapid emergency access.

Washing with water is the emergency measure to use when skin or eyes are exposed to anhydrous ammonia. Time is important! Get water onto the exposed area of the skin or eyes immediately and flush for at least 15 minutes. Never wear contact lenses when handling anhydrous ammonia, since they can trap the gas and freeze the contacts to the eye. Contaminated clothing should be removed quickly but carefully. Thaw clothing frozen to the skin with water before attempting removal. Wash the affected skin area with abundant amounts of water and do not apply anything except water for the first 24 hours. Stay warm and get to a physician immediately.

Care and Maintenance of NH³ Tank

Anhydrous ammonia can be handled and used safely. It is imperative that all equipment is properly maintained and checked daily. A regular, scheduled maintenance program will ensure that all the valves and the tank are safe for handling the high pressure liquid and its vapor form. Perform a daily visual inspection to locate any defects in the tank or hoses. To handle NH³ safely, all equipment must function properly. The most important valves and components that must be routinely checked are listed below. For a more detailed explanation, refer to External Visual Inspection Guidelines for Anhydrous Ammonia Nurse Tanks Applicators Tank Appurtenances, published by:

The Fertilizer Institute (TFI)
501 2nd St. N.E.
Washington, D.C. 20002

Important Valves And Components List

• Liquid Withdrawal Valve- Be sure valves are functional and will shut off. Any leak detected in the valve is cause for immediate repair or replacement. The valve should be removed every five years and inspected for internal corrosion and thread deterioration. At this time, check the excess flow for (1) movement of the valve plunger, (2) corrosion of springs, valve seat and guide, and (3) out of round disk.

• Liquid Fill Valve- ( Same inspection procedure as liquid withdrawal valve.)

• Vapor Return Valve- (Same inspection procedure as liquid withdrawal valve.)

• Pressure Gauge- Check the consistency with other tanks of similar volume. Make sure the lens is clean and the dial face is clearly readable.

• Fixed Liquid Level Gauge- Clean, repair or replace as needed.

• Liquid Level Float Gauge- Check against the 85% level gauge for accuracy. An inaccurate reading, leaking at the seal, or unreadable lens should be repaired or the defective item replaced.

• Safety Relief (SR) Valve- Stand to one side and use a mirror for viewing. The SR valve should be free of dirt and rust. Replace the rain cap if it is damaged or missing. Leakage or discharge below 250 psi is cause for replacement. The SR valve should be replaced every five years.

• Hydrostatic Relief (HR) Valve- Inspect the valve for leakage, corrosion or damage. The HR valve should be replaced every five years.

• Transfer Hose- Examine the hose closely for cuts, abrasions, soft spots, bulges, kinking or flattening and similar defects. Check for slippage of the hose at coupling. The hose must be replaced five years from the date of manufacture (stamped on hose).

• Tank Condition- Prevent corrosion and excessive pressure buildup from direct sunlight by keeping the tank painted with a reflective paint. Dented or damaged tanks should be taken out of service until checked by an authorized inspector and repaired as necessary. All welding on the tank must be done by a certified welder. Be careful in repairing or replacing these parts to prevent accidental exposure to anhydrous ammonia. Most retailers will assist you in repairing your nurse tank or applicator.

IMPORTANT SAFETY POINTS

• Always have an ample water supply

• Always wear personal protective equipment Never fill a tank over 8-5 percent of the tank's capacity Inspect and replace hoses and valves as needed Bleed off pressure in the hose before disconnecting it

• Stay clear of hose and valve openings

• Follow step-by-step procedure when using the equipment

• Never try to repair the tank yourself; Seek a qualified technician

• Never tamper with relief valves

• Use a proper hitch, safety chains and a Slow Moving Vehicle (SMV) sign when towing on the highway

Labels, Marking & Safety Signs Legal Requirements

Standard Recommendations

The American Society of Agricultural Engineers (ASAE) has developed a number of general safety standards which contain requirements that should be applied to anhydrous equipment. ASAE S441 establishes requirements for uniform safety signs to promote safety of persons associated with agricultural equipments. This includes:

• Signal Words (Caution, Warning or Danger).

• Sign Format (See Page 4).

• Sign color combinations (Black background and yellow lettering for caution and warning signs and red background with white lettering for danger signs).

• Letter Sizes and durability requirements.

These safety signs should be strategically placed in the immediate vicinity of the hazard and be readily visible so that the viewer can avoid the hazard or take other appropriate action. In consideration of these requirements and the multiple concerns for various safe operating procedures mentioned previously, several standard safety signs (illustrated below) should appear on the equipment used in handling and application of anhydrous ammonia.

Additional ASAE safety standards require the following:

• An operator's manual. It is extremely important that this manual be with the equipment and available for reference at all times.
• A safety type hitch pin with a standard safety chain attachment for the nurse tank wagons or running gear.
• In addition to the mandatory SMV sign, appropriate lighting for travel on roadway must include at least one red tail lamp and two amber flashing warning lamps. These may be on the towing vehicle or the tank wagon, but they must be visible from the rear. Additionally, the tank wagon must have at least two red reflectors visible to the rear.
• Turn signals, flashing warning lights and a red brake light are recommended on all anhydrous ammonia tank wagons which are towed on public roadways. To accommodate these lights, a standard seven terminal breakaway connector plug should be used on the tank wagon.
• At least one safety sign should be located in between the control valves and the 5 gallon water supply.

Highway Safety

The speed limit for anhydrous ammonia tanks traveling on the public roadways of Ohio is 25 M.P.H. and only one nurse tank may be towed. Prior to operating a nurse tank on public roadways the following should be carefully checked:

Running Gear - Inspect the farm wagon frame tongue, reach poles, anchor devices, wheel bearings, knuckles, ball joints and pins for structural damage, cracks, excessive wear and adjustments.

Tires - Check for proper inflation, cuts, badly worn spots, and signs of weathering. Assure that lug nuts are tight.

Lubrication - Steering knuckles, wheels, tongues, or other applicable farm wagon equipment should be lubricated at least once every year.

It is highly recommended that the vehicle used to tow the nurse tank be at least equal in weight to the gross weight of the nurse tank. This will assist the operator in maintaining control of all the vehicles, at 25 M.P.H., and minimize the potential for an accident.

Any tank operating on the highways should look similar to the above drawing. Regulations require: An SMV emblem be attached to the rear of the vehicle and visible from at least 500 feet; The words Anhydrous Ammonia (4 inches high) in contrasting colors be placed on both sides and the rear of the tank; The words Inhalation Hazard (3 inches high) in association with the anhydrous ammonia label be on both sides of the tank; The DOT placard for non-flammable gas be placed on the front, back and sides of the tank.