Anhydrous Ammonia

Chapter 296-826, WAC

Effective Date: 09/01/06


WAC 296-826-600


For printing


To protect employees while transporting, transferring, loading and unloading anhydrous ammonia

Mounting containers on trucks, semi-trailers and trailers

Mounting containers on farm trucks or trailers for transporting ammonia

Tank car loading or unloading

General specifications

Additional requirements for systems mounted on trucks, semi-trailers, and trailers for transporting ammonia
Nonrefrigerated containers
Refrigerated tanks


WAC 296-826-60005

Mounting containers on trucks, semi-trailers and trailers

You must

  • Make sure the method for attaching any container to the cradle, frame, or chassis of a vehicle is based on both of the following:
    • -Two "g" loading in either direction
    • -Using a safety factor of at least 4 based on the maximum strength of the material used.



Two "g" is either of the following:

    • -For load support it's equivalent to 3 times the static weight of the supported articles
    • -For loading and bending, acceleration, and torsion it's equivalent to twice the static weight support applied horizontally at the road surface.

You must

  • Secure both ends of the hose during transit.
  • Follow the requirements in Table 14, Additional Container Mounting Requirements.

Table 14
Additional Container Mounting Requirements

If you have:


"Hold-down" devices

  • Anchor the container to the cradle, frame, or chassis so there's no area of unnecessary stress
  • Lock the container down tightly
  • Provide stops or anchors to minimize movement between the container and the framing

    Note:   Movement could be the result of stopping, starting or changing direction.

Vehicles with cargo tanks designed with stress members instead of a frame

  • Support the tank with external cradles suspended at least 120 degrees of the shell circumference
  • The design calculation needs to include all of the following stressors:
    • -Beam
    • -Shear
    • -Torsion
    • -Bending moment
    • -Acceleration
    • -Any other stresses covered by the code of the cargo tank design.

A liquid withdrawal line installed in the bottom of a container

  • Then make sure the connections to the container, including the hose, aren't lower than the lowest horizontal edge of the trailer axle.

A cradle and container that aren't welded together

  • Use suitable material between them to eliminate metal-to-metal friction.


WAC 296-826-60010

Mounting containers on farm trucks or trailers for transporting ammonia

You must

  • Make sure tanks mounted on farm trucks and trailers meet all of the following:
    • -Are securely attached using drawbars and safety chains
    • -Follow behind the towing vehicle without swerving
    • -Have at least 5 gallons of readily available clean water.
  • Do all of the following when mounting containers on farm trucks:
    • -Use suitable material between the cradle and the container to eliminate metal-to-metal friction
      • This isn't necessary if the cradle and container are welded together
    • -Use stops and hold down devices to prevent displacement.
  • Distribute the container's weight, when mounted on 4-wheel farm trucks or trailers, evenly over both axles.

WAC 296-826-60015

Tank car loading or unloading

You must

  • Establish a location for tank car loading and unloading operations.
  • Assign employees and instruct them in the unloading of tank cars.
  • Make sure, when unloading cars, to set the brake and block the wheels.
  • Make sure the track of tank siding is level.
  • Place caution signs on the track or car to warn approaching persons of loading and unloading operations that are:
    • -Kept in place until the car is unloaded and disconnected from discharge connections.
  • Make sure these caution signs meet all of the following:
    • -Are made of metal or other suitable material
    • -Are at least 12 to 15 inches in size
    • -Read either "Stop -Tank Car Connected" or "Stop Men
      at Work" meeting the following criteria:
      • "Stop" at least 4 inches high
      • All other words at least 2 inches high
      • All with white letters on a blue background.


WAC 296-826-60020

General specifications

You must

  • Get owner authorization to use transfer containers.
  • Make sure transfer containers are gauged and filled in either:
    • -Open atmospheres
    • or
    • -Buildings approved for that purpose.
  • Make sure pumps used to transfer ammonia meet all of the following:
    • -Have a manufacturer's label for ammonia service
    • -Are designed for at least 250 psig working pressure
    • -Have a constant differential relief valve discharging into the suction port that:
      • Is installed on positive displacement pumps
      • Meets the pump manufacturer's recommendation for the settings and installation
    • -Have a pressure gauge graduated zero to 400 psig installed on the discharge side before the relief valve line.
  • Make sure plant pipes with shut off valves are located as close as possible to the pump connections.
  • Make sure meters used for measuring liquid anhydrous ammonia:
    • -Are recommended and labeled for ammonia service by the manufacturer
    • -Are designed for a minimum working pressure of 250 psig
    • -Incorporate devices that prevent unintended measurement of vapor.
  • Do the following when transferring ammonia:
    • -Maintain ammonia at a temperature suitable for the receiving container
    • -Have at least one attendant supervise the transfer from the time connections are made to when disconnection occurs
    • -Don't use flammable gases or gases that will react with ammonia, such as air to unload tank cars or transport trucks.
  • Make sure compressors used for transferring ammonia meet all of the following:
    • -Have a working pressure of at least 250 psig when transferring ammonia.
    • -If crank cases of compressors aren't designed to withstand system pressure, then provide protection with a suitable safety relief valve
    • -Are connected to plant piping with shut off valves located as close as practical to compressor connections
    • -Have a safety relief valve that's both:
      • Large enough to discharge the full capacity of the compressor
      • Connected to the discharge before any shut off valve
    • -Have an oil separator on the discharge side, where necessary to prevent contamination
    • -Have a drainable liquid trap or other adequate method on the compressor suction to minimize the entry of liquids into the compressor
    • -Pressure gauges on the suction and discharge ends 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:
    • - Backflow check valves

    • or

    • - Properly sized excess flow valves.



If such valves aren't practical, remotely operated shut off valves may be installed.

WAC 296-826-60025

Additional requirements for systems mounted on trucks, semi-trailers, and trailers for transporting ammonia

You must

  • Make sure the content of vehicle containers is determined by one of the following:
    • -Weight
    • -Liquid-level gauging devices
    • -Meters
    • -Other approved methods.
  • Use a thermometer well when the content of a container is determined by liquid-level measurement.   Make sure of the following:
    • -The volume, when converted to weight, doesn't exceed the DOT filling density requirement.
  • Protect pumps and compressors against physical damage when mounted on trucks or trailers.
  • Unload tank motor vehicles with a water capacity greater than 3,500 gallons at approved locations.


WAC 296-826-60030

Nonrefrigerated containers

You must

  • Make sure filling densities for nonrefrigerated containers are below or equal to the requirements in Table 15, Filling Densities.

Table 15
Filling Densities


Aboveground Containers

Underground Containers









  • For uninsulated, aboveground containers, the 56% corresponds to:
    • -82% by volume at -28° F
    • -85% by volume at 5° F
    • -87.5% by volume at 30° F
    • -90.6% by volume at 60° F

WAC 296-826-60035

Refrigerated tanks

You must

  • Make sure refrigerated tanks aren't liquid full at a liquid temperature so that the vapor pressure is below the "start-to-discharge" pressure setting of the safety relief valve.

WAC 296-826-60040


You must

  • Permit welding only on the saddle plates, lugs, or brackets attached to the container by the manufacturer.


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