Pipeline Safety: Class Locations and Valve Placement

In a recent interview about pipeline safety, senior health and safety advisor Dale Gross recommended installing valves at closer intervals to allow you to isolate smaller sections of the pipeline.

Pipeline valve spacing is covered under Title 49 of the Code of Federal Regulations. The responsible regulatory entity is the Pipeline and Hazardous Materials Safety Administration (PHMSA), which is part of the U.S. Department of Transportation. Below you’ll find the minimum safety standards for the spacing of valves along pipelines transporting natural and other gas.

Class locations and valve spacing on transmission lines

Pipeline locations are classified based on their proximity to buildings (especially those intended for human occupancy) or other areas where people gather regularly. A “class location unit” is an onshore area extending 220 yards (660 feet) on either side of any pipeline longer than 1 mile.

All onshore transmission pipelines are required to have block valves (i.e., valves intended to block flow) stationed at specified intervals, “unless in a particular case the Administrator finds that alternative spacing would provide an equivalent level of safety.”

Class 1 locations

Definition: A Class 1 location is:

  • Any offshore area, or
  • Any class location unit that has 10 or fewer buildings intended for human occupancy

Valve placement: Each point on a pipeline in a Class 1 location must be within 10 miles of a valve.

Class 2 locations

Definition: A Class 2 location is any class location unit that has between 11 and 45 buildings intended for human occupancy.

Valve placement: Each point on a pipeline in a Class 2 location must be within 7½ miles of a valve.

Class 3 locations

Definition: A Class 3 location is:

  • Any class location unit that has 46 or more buildings intended for human occupancy, or
  • An area where the pipeline lies within 100 yards (300 feet) of either a building or a small, well-defined outside area (such as a playground, recreation area, outdoor theater, or other place of public assembly) that is occupied by 20 or more persons on at least 5 days a week for 10 weeks in any 12-month period.

Valve placement: Each point on a pipeline in a Class 3 location must be within 4 miles of a valve.

Class 4 locations

Definition: A Class 4 location is any class location unit where buildings with four or more stories above ground are prevalent. *Note that this definition does not specify that the buildings be intended for human occupancy.

Valve placement: Each point on a pipeline in a Class 4 location must be within 2½ miles of a valve.

Other transmission line valve requirements

In addition to the block valves, each onshore section of a transmission line must have a blowdown valve that has enough capacity to allow the transmission line to be blown down rapidly, and the gas must be able to be blown to the atmosphere safely.

Distribution line valves

Distribution lines also require valves so that the system can be shut down as quickly as possible in an emergency. The placement of valves along distribution lines is determined by the operating pressure, the size of the mains, and the local physical conditions. Every regulator station in a gas distribution system must also have a valve installed at a sufficient distance so that if the station can’t be accessed, the valve can still be controlled.




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