David
E. Baker
University of Minnesota Extension Service
Anhydrous
ammonia is one of the most efficient and widely used sources
of nitrogen for plant growth. The advantages of ammonia's
relatively easy application and ready availability have led
to its increased use as a fertilizer on Missouri farms.
Anhydrous
ammonia also has disadvantages, especially in its handling.
It must be stored and handled under high pressure, which requires
specially designed and well-maintained equipment. Workers
also must be trained to handle this product and to follow
strict work procedures to ensure operator safety.
What
is anhydrous ammonia (NH3), and why is it so risky to handle?
It is a chemical made up of one part nitrogen (N) and three
parts hydrogen (H3). The physical properties of this fertilizer
make it one of the most potentially dangerous chemicals on
the farm.
Anhydrous
means without water. Consequently, when anhydrous ammonia
and moisture come into contact, they rapidly combine. When
it is injected into the soil, the liquid ammonia expands into
a gas and is readily absorbed in the soil moisture. Similarly,
the liquid or gas that contacts body tissue - especially the
eyes, skin and respiratory tract - will cause dehydration,
cell destruction and severe chemical burns. Victims exposed
to even small amounts of ammonia require immediate treatment
to avoid permanent injury.
Table
1. Concentration of anhydrous ammonia vapor. |
PPM(parts
per million) |
Percent
by volume |
Effects
on the human body |
5 |
0.005 |
Detectable
by almost all persons. Some people complain of nose irritation
after 5 minutes |
134 |
0.0134 |
Most
people experience dryness and irritation of nose, throat
and eyes. |
700 |
0.07 |
Coughing.
Severe eye irritation, if not treated, may lead to partial
or total loss of sight. |
1700 |
0.17 |
Serious
lung damage, death unless treated. |
2000 |
0.2 |
Burns
and blisters skin after a few seconds of exposure. |
5000 |
0.5 |
Death
by suffocation within minutes. |
Anhydrous
ammonia has a built-in safety factor - you can't stand to breathe
it. No one can voluntarily remain in a concentration of anhydrous
ammonia gas strong enough to damage the nose, throat, lungs,
eyes or skin. When people receive burns or eye damage from the
product, it is because of a sudden release of it where the victim
is unprotected and cannot escape. Table 1 gives examples of
the effects of various concentrations of anhydrous ammonia vapor
on the human body.
Under
atmospheric temperature and pressure, anhydrous ammonia is
a colorless gas with a sharp, penetrating odor. For use as
an agricultural fertilizer, it is compressed into a liquid
resembling water. In the liquid state, under pressure, it
is stored in specially made tanks strong enough to withstand
internal pressures of a minimum of 250 pounds per square inch
(psi). As the outside temperatures increase, the temperature
of the anhydrous ammonia increases, causing the vapor pressure
in the tan to increase. For example, at 60ø F, the pressure
is 93 psi and at 100ø F, the pressure is nearly 200 psi.
Ammonia
is corrosive to certain metals and their alloys, such as copper
and zinc. Galvanized pipe and brass fittings must not be used
with equipment used for storing or applying ammonia. Containers
should be made of high-strength steel or other suitable material
and fittings should be made of black iron.
Due
to its properties and the manner in which it is stored, anhydrous
ammonia can create a dangerous situation when it is accidentally
released. The following are some examples of misusing anhydrous
ammonia and its equipment that can result in accidents:
- Filling
tanks beyond recommended capacity.
- Knocking
open the hose-end valve accidentally.
- Moving
the applicator tank before filling hoses have been disconnected
from nurse tank.
- Venting
pressure release valve while a person is in line of discharge.
- Breaking
of transfer hose, especially an old or misused one.
- Failing
to bleed hose coupling before disconnecting.
- Rupturing
of low pressure hose due to pressure buildup when knives
plug.
- Releasing
ammonia when knives are unplugged.
- Overturning
an applicator or nurse tank while in transit or in the field.
All
of the above accident situations can result in injury, extensive
property damage or both.
To minimize
the chance of an accident, take steps to ensure all equipment
is in top operating condition. Be sure all agricultural workers
handling or applying ammonia have been specially trained in
equipment maintenance and operation, proper personal protective
equipment and emergency first aid.
Even
with the best precautions, you may be involved with the accidental
release of ammonia. Simple protection can prevent serious consequences
if used consistently.
A face
shield or goggles, rubber gloves and a heavy-duty long-sleeved
shirt are recommended as minimum protection for operators
routinely handling ammonia. Wear gloves and eye protection
whenever you are working on or operating anhydrous equipment
or handling hoses.
It is
important to wear properly fitting goggles or a face shield
when working with ammonia. A face shield will help prevent
you from breathing a direct blast of ammonia and also will
reduce possible eye exposure. Regular glasses do not provide
adequate protection. Never wear contact lenses when working
with ammonia. Ammonia might get under the lenses and cause
permanent eye damage before you can remove the lenses and
flush your eyes with water.
Loose-fitting
rubber gloves with an extended cuff are recommended for handling
anhydrous ammonia. Turn the extended cuff down so ammonia
does not run down your sleeve when you raise your arms. You
can remove gloves that fit loosely in case of an emergency.
You
can further protect your arms from splashes by wearing heavy-duty
clothing such as coveralls or work shirts that cover your
arms. Thin dress shirts or short sleeves don't provide satisfactory
protection.
If you
store bulk quantities of anhydrous ammonia on your farm, you
will need additional protective equipment. Keep two rainsuits
or slickers and gas masks with an ammonia canister filter
available for emergency work. The protection from a canister
filter is limited and you should only use it in low concentrations
of ammonia. When a serious leak occurs, call your local fire
department for assistance. Firefighters have the proper training
and equipment - including a self-contained breathing apparatus
and protective suit to deal with major ammonia leaks where
high concentrations of ammonia are probably present.
The
operator's manual for anhydrous ammonia equipment should include
instructions on proper procedures and protective equipment
to use when handling ammonia. Review this information before
operating the equipment.
Every
second is critical when someone is sprayed with liquid ammonia
or engulfed in concentrated vapors. Exposure to anhydrous ammonia
can be harmful if it contacts the skin and eyes or if it is
inhaled or swallowed. When ammonia contacts the skin or eyes,
tissue damage occurs rapidly. Immediately flushing the exposed
body area(s) with water is crucial.
Regulations
require that all farm vehicles used for anhydrous ammonia
carry a container filled with at least 5 gallons of water.
This water must be readily available for flushing the eyes
and skin in case of exposure. You should change the water
daily to ensure you have a clean supply.
Safety
specialists recommend you keep a second 5-gallon container
of water on the tractor. This provides another source of water
for first aid in case the tractor operator is unable to reach
the water container on the nurse or applicator tank. You should
also carry a 6- to 8-ounce, water-filled plastic eye wash
bottle in your shirt pocket. It provides an immediate supply
of water if an accident does occur. The objective of the eye
wash bottle is to get the excess ammonia out of the eyes in
the first few seconds until you or the victim can get to the
larger water supply to continue flushing.
When
a victim has been exposed to anhydrous ammonia, move him or
her to a safe place and flush the exposed area immediately
with water for a minimum of 15 minutes. Remove contaminated
clothing as soon as you have thawed them out. (Remember, the
sub-zero temperature of anhydrous ammonia can freeze exposed
clothing to skin below it. If you remove clothing before you
thaw it with rinse water, extensive skin damage can result.)
Do not
apply salves, creams or ointments. They won't stop the damaging
action to skin. Contact a doctor immediately after emergency
first aid treatment.
Even
if small amounts of ammonia enter the eyes, irrigate them
immediately with water for 15 minutes or more. Hold the eyelids
open during irrigation to ensure water contacts all parts
of the eye. Immediate first aid is important to avoid partial
or total loss of vision. Again, consult a doctor after giving
emergency first aid.
Ammonia
vapors are easily detected because of their pungent odor,
even in low concentrations. Inhaling ammonia can irritate
the respiratory tract and lungs. At high concentrations, ammonia
combined with the moisture in the lungs may damage the lung
lining and reduce the lungs' ability to transfer oxygen to
the bloodstream.
When
a person has inhaled ammonia, move them to a safe area. Exposures
to low concentrations of ammonia for a short period of time
may not require treatment. Exposure to higher concentrations
may cause convulsive coughing and respiratory spasms. Provide
cardiopulmonary resuscitation if the victim is not breathing.
Obtain medical help as soon as possible.
In case
ammonia has been swallowed, contact a doctor immediately.
Have the victim, if conscious and able, drink large amounts
of water to dilute the chemical. Do not induce vomiting if
the victim is in shock or unconscious. If vomiting occurs,
keep the head lower than the hips to prevent vomitus from
entering the lungs.
The
specially fabricated and designed pressurized equipment should
meet the guidelines provided by the American National Standards
Institute in publication K61.1-1981, Safety requirements for
storage and handling of anhydrous ammonia. All parts and contact
surfaces must withstand a minimum working pressure of 250 psi.
This includes pressure welds, safety valves, gauges, fittings,
hoses and metering devices.
All
containers used for storing ammonia must be painted white
or silver. Light colors reflect heat and this helps keep the
temperature and pressure down inside the tank during warm
weather.
Keep
anhydrous ammonia equipment in good condition. Be on the lookout
for defects in nurse tanks, regardless of whether you own them
or lease them. Make periodic inspections and repair or replace
equipment. Accident victims are just as injured regardless of
who owns the tank. The following procedures for maintenance
are taken from guidelines recommended by the Fertilizer Institute.
For a complete copy of the detailed guidelines, write to: The
Fertilizer Institute, 1015 18th St. NW, Washington, D.C. 20036.
Daily
inspection. Each day give the tank and hoses a brief inspection.
Look for problems with:
- Hoses
- Check for cuts, soft spots, bulges, kinking, flattening
or slipping at the coupler.
- Tires
- Inspect for proper inflation, cuts, weathering, wear and
tightness of lug bolts on wheels.
Each
time you fill the nurse tank, check the liquid level gauge
and pressure gauge. The gauges should be working properly
and be consistent in their readings. Don't use nurse tanks
with faulty gauges. To repair or replace faulty gauges, the
tank must be emptied and the tank pressure dropped to zero
before faulty parts can be removed.
Immediate
repair. Several situations are cause for immediate repair
or replacement. Any leak in a liquid or vapor shut-off valve
calls for repair or replacement of the valve. If an accident
causes a dent, gouge, crack or other damage to the tank that
might result in failure, inspect the tank, and if necessary,
repair it before placing it back into service. A certified
welder must make any welding repairs on the tank and the welds
must be hydrostatically tested to ASME standards. An overturned tank or collision between the tank and other farm machinery
are examples of causes for inspection.
Annual
inspection. At least once a year, inspect these items
carefully and repair or replace as needed:
Hoses.
Lay hose out straight and examine carefully for:
- cuts
exposing reinforcement fabric
- soft
spots or bulges
- blistering
or loose outer cover
- unusual
abuse, such as kinking or flattening by a vehicle
- slippage
of hose at any coupling
- brass
or copper fittings or waterhose-type clamps
- hoses
over 1/2 inch O.D. not marked with the following information:
- "Anhydrous
Ammonia"
- xxx
psig (maximum working pressure)
- Manufacturer's
name or trademark
- Year
of Manufacture
Braid
material |
From
date of installation |
Rayon |
2
years |
Nylon/Kevlar |
4
years |
Stainless
steel |
6
years |
Immediately
replace hoses that show these defects. Hoses exposed to anhydrous
ammonia lose strength. You should replace them according to
the following schedule regardless of visible damage:
Most
ammonia accidents involve improper handling procedures. Read
your owner's manual an follow instructions. Do not leave during
the transfer procedure. Check with your dealer if you are unsure
about the correct procedure. Ask for instructions when renting
or borrowing equipment. Review the procedures with farm workers
before allowing them to handle equipment to ensure their safety.
When
filling a nurse or applicator tank, be thoroughly familiar
with the equipment and procedures prior to any transfer. Because
most accidents occur when transferring ammonia, it is very
important to wear a protective face shield or goggles and
rubber gloves when you are involved in this procedure.
Be sure
the 5-gallon container is full of clean water.
Park
the nurse tank on level ground, downwind from the filling
operation. Place it close to the operation to eliminate any
stress on the hose. Avoid working near any obstacles that
would make evacuation difficult, such as fences, buildings
or ditches. Block the wheels to prevent the nurse tank from
moving. A serious situation could develop if the tank moved
and a hose tore loose during the filling operation.
Before
connecting the hose, make sure the coupling and connections
are free of dirt and other foreign material. Visually check
to see that the threads are not damaged. This will reduce
the chance of an ammonia leak when pressure is applied.
Workers
should carry the filler hose by the valve body or coupling,
not by the valve wheel. This reduces the chance of the valve
wheel opening and spraying ammonia. Remember the valve wheel
and fitting are designed to be closed by hand pressure only.
Don't use a wrench - it can damage the fitting.
If you
are using a compressor to transfer ammonia, follow recommended
instructions in your operator's manual. Maintain a vapor pressure
5 to 10 pounds lower in the tank being filled to keep a forward
flow.
Do not
overfill the nurse or applicator tank. Keep check on the liquid
level by opening the 85 percent fill bleeder valve. A white
fog will appear when it reaches this level. As a part of the
normal loading procedure, check the liquid level float gauge
accuracy by comparing it with the fixed liquid level gauge.
It is important to fill only to 85 percent or less of the
total liquid capacity of the tank. As the outside temperature
increases, the temperature of the liquid increases and the
liquid expands, causing the vapor pressure in the tank to
increase. If the tank is overfilled and no vapor space is
available, the safety relief valve might fail, causing the
tank to rupture or explode.
After
the filling operation is complete, secure the hose in the
storage position for transit. Take a final walk around the
nurse or applicator tank to confirm that all steps have been
taken.
Prevention
and precautions
Work
upwind! Work upwind of machinery, the hose-end valve, bleeder
valve, coupler or plugged applicator tubes. This gives an advantage
of getting away quickly if anhydrous ammonia is suddenly released.
Plan an escape route. Know which way to run.
Handle
valves with care! Grasp valves by the valve body or the
coupling, not by the valve handle. The valve handle might
accidentally turn and open. If you throw a hose with an end
valve over the tank, it might open when it hits the tank and
spin open the rest of the way. All tanks are fitted with excess
flow valves that operate automatically when a hose ruptures.
A carelessly handled valve that is partially opened may not
provide adequate flow to activate the excess flow valve and
the entire tank of ammonia could escape. Attach the end coupling
to the dummy fitting provided when transporting or not using
the hose.
Respect
pressure! You must release pressure from the coupler using
a bleeder valve before disconnecting the coupler. Bleed the
pressure off slowly and then disconnect the coupler immediately.
On a warm day, leaving a coupler connected for five to 10
minutes after bleeding allows ammonia in the hose to rebuild
pressure. On cold days, rubber seals are stiff and may not
seal completely. The resulting leak might spray anhydrous
ammonia vapors as the tank valve is opened. It also may create
cloud of vapor, limiting access to the equipment for reclosing
the valve.
Check
your safety water tank! Check this water supply (at least
5 gallons) daily. It may freeze in cold weather or become
too hot to safely flush eyes on warm sunny days.
Change
the water weekly. It might absorb ammonia from the air
and become contaminated. Carrying a water supply on both tank
and tractor gives extra protection.
Check
applicator tubes! When removing dirt from a plugged applicator
tube, treat it as if it contains pressurized anhydrous ammonia.
They often do. This could be of particular concern when you
work among the knives of an anhydrous ammonia applicator.
You might not be able to move fast enough to escape the pungent
fumes without injury.
Leave
a message! Co-workers should know each other's activity
schedule when applying anhydrous ammonia. An overdue operator
may have had an accident. An accident causing eye damage leaves
the operator helpless and stranded. Check if you see operators
stopped in the field for an unusual period of time when conditions
are normal and equipment should be moving.
Towing
a nurse tank presents problems because anhydrous ammonia is
a hazardous material. An accident with a nurse tank on the highway
could result in serious injury, costly repairs and liabilities.
Nurse
tanks of 3,000 gallons or less mounted for transport are considered
"implements of husbandry" when they are used exclusively for
agricultural purposes. Nurse tanks must have the words "anhydrous
ammonia" in large green lettering and a non-flammable gas
placard with the words "non-flammable" or "1005" on both sides
and on each end of the tank. Applicator tanks must contain
the same identification on at least the rear of the container.
Motorists on the highway can easily identify an ammoni tank
by these markings.
All
nurse tank wagons must be securely attached to the vehicle
pulling them. Use a drawbar, hitch pin, safety clip and a
safety chain. Before each highway trip, check the hitch pin,
safety clip and safety chain to see that they are secure.
Nurse
tank wagons are designed to follow smoothly in the path of
the towing vehicle. Nurse tanks can overturn or collide with
another vehicle if the tank wagon swerves from side to side.
Make sure your tank wagon is hooked up properly. Also make
sure the wheel lug nuts are tight and the tires are in good
shape and properly inflated.
When
hauling a loaded nurse tank, drive at speeds of 30 mph or
less. The potential for a serious accident is increased at
higher speeds, because you might lack sufficient braking capacity
to safely control the wagon. Hauling more than one loaded
nurse tank is a violation of Missouri law.
Because
farm implement tires are designed for travel at low speeds,
allow sufficient time to reach your destination. When towing
at 25 mph or less, display a slow-moving-vehicle sign on the
wagon.
State
law has additional requirements for towing a nurse tank or
applicator tank at night. You must display two red reflectors,
visible to the rear, at the extreme right and left projections
of the trailing unit. If the brake and turn lights on the
towing vehicle are obscured, you must put brake and turn lights
on the nurse or applicator tank.
In
addition to its use as a nitrogen fertilizer, anhydrous ammonia
has other purposes on the farm. It has been used with high-moisture
grains to control mold growth. When using it with grain, use
the same precautions that you use when applying it as fertilizer.
The same hazards exist whenever you handle ammonia under pressure.
Anhydrous
ammonia also is used to add non-protein nitrogen to corn silage.
The ammonia is under pressure up to the cooling reactor in
this application. Wear a face shield or goggles and rubber
gloves along with heavy-duty clothing, including long-sleeved
shirts, when connecting and disconnecting the ammonia hose
and fitting.
Anhydrous
ammonia is perhaps the most dangerous chemical on the farm.
It can be handled safely when you follow proper procedures.
Make sure you wear personal protective equipment and provide
plenty of clean water for first aid. Keep the equipment in good
condition and observe proper procedures when transferring ammonia.
When transporting ammonia on the highway, travel at a safe speed
and use a safety chain and a safety clip on the hitch pin. By
following recommended procedures, you can reduce he chance of
an accident.
- The
Fertilizer Institute, External Visual Inspection Guidelines
for Anhydrous Ammonia Nurse Tanks and Applicator Tanks,
1982.
- American
National Standards Institute, Inc., Safety Requirements
for the Storage and Handling of Anhydrous Ammonia, Publication
K61.1-1981.
- Aherin,
Robert and Lee Schultz, Using Anhydrous Ammonia Safely on
the Farm, Educational Package AG-EP-2192, Agricultural Extension
Service, University of Minnesota, 1984.
- National
Safety Council, Safe Handling of Anhydrous Ammonia, Accident
Prevention Bulletin 699.41-11.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This document is
GO1920
, published by the University Extension, University of
Missouri-Columbia, Columbia, MO 65211. Publication date: October
1993.
David
E. Baker, Department of Agricultural Engineering, University
Extension, the University of Missouri-Columbia, Columbia,
MO 65211.
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