The partial plugs would have severely restricted the sprinkler discharge. Even though these sprinkler systems were relied upon heavily to protect the building and contents during a fire, they had never before been internally inspected and, as a result, how long the systems were out of service could not be determined. The impaired systems could not have provided its intended protection and the plant was actually, unknowingly, sitting there vulnerable to a catastrophic loss potential. Ice plugs usually cannot be detected unless piping is taken down and internally inspected. Routine testing of low air pressure and waterflow alarms cannot be used to detect ice plugs.
Plugs typically form in piping exposed to large temperature differentials.
The moisture in the compressed air on the dry side of the sprinkler system condenses and the water freezes inside the piping at the point where it enters the freezer. In order to reduce moisture content in piping, the air supply used by the compressor should be taken from the room with the lowest temperature. Also, excess water left in piping after yearly trip tests or accidental system trips will result in ice plugs forming. Visual inspections of piping should be conducted annually to ensure systems are free of ice plugs. All rights reserved.