In a food processing facility, an employee moved a pallet from an upper storage rack using a forklift when the forks were lifted too high and contacted the roofing panel near an ammonia line. The roofing panel pushed up, bending the liquid ammonia refrigeration line. A two-bolt flange connection was strained, causing an uncontrolled leak past the sealing gaskets of the flange. The building was evacuated, and the leak released over 1,000 lbs. of ammonia into the building and atmosphere.
The building is a 110,000-square-foot industrial food processing facility built in 2000. The facility employs approximately 430 workers and comprises warehouses, food processing areas, and office spaces.
The facility has multiple areas for refrigerating or freezing food products and has a large refrigeration system containing approximately 8000 pounds of ammonia.
Ammonia concentrations of up to 4000 parts per million (ppm) were measured inside the building from personal sensors in the area of the piping damaged by emergency response personnel. The system leaked approximately 1100 pounds of ammonia indoors and into the atmosphere before the ammonia line was able to be isolated, and the leak stopped.
The refrigeration and freezer areas are insulated areas constructed within the building consisting of insulated walls and ceilings. The refrigeration lines for the condensers in the areas mostly run on the outside of the insulated panels and only enter when they drop down to connect to the condensers. The lines are suspended from the metal ceiling structures and run in a mezzanine above the insulated ceiling panels. (e.g., this is commonly called an “interstitial space.”
Statements
Managers and safety personnel
- The employee who was operating the forklift that struck the ceiling had been employed for about two years and had been working in the receiving department operating a forklift for over a year.
- The employee had received forklift training and a qualification to operate the equipment and was familiar with the equipment.
- The employee had worked in the specific area and performed the same tasks before.
- There had not been any recent changes to area the employee was operating the forklift in.
- The forklift operates in different areas with different ceiling heights and needs to be able to reach higher than the ceiling height in the receiving area
while working in the freezer.
Documents
Refrigeration contractor report
- The area of the ammonia leak was from a two-bolt flange where the sealing gasket was damaged by the upward force on the pipe.
Forklift specification
- The maximum lift height of the forklift is 31 feet.
Site assessment
- The ceiling height in the receiving area was measured at 21 feet from the floor.
- The ceiling height in the freezer area was approximately 30 feet from the floor.
The cause of the incident was physical contact between the mobile forklift equipment and the ammonia line.
The contributing factors to the incident include:
- The 1/2-inch ammonia line being installed without sufficient clearance or protection from the material handling equipment below.
- No identification of the location of the ammonia lines from the work area below.
- The reliance on the forklift operator’s actions to not raise the forks high enough in the work area to contact the ceiling panels under the refrigeration lines.
Yellow = Where PIT struck ceiling panel
Red = where the pallet was stored
WARNING! Although not mentioned in this report, we STRONGLY ENCOURAGE clients to make these storage locations unusable by welding in bars to prevent activity directly under ammonia handling equipment such as this evaporator shown in this pic!
Green = Insulated ammonia line contacted by insulated ceiling panel
Blue = Area of ammonia leak from a flange connection
Red Arrow = The distance the insulated panel was pushed up by the forklift
Source: https://assets.contentstack.io/v3/assets/bltdec2ded849740f4d/blt303b1f7ded1d6f5f/651f08adf64f152d61b472d0/II-1508412-2023-(31811).pdf