Per AGA, 49 CFR 192, ASME B31.8
Understand TBS design, Joule-Thomson cooling, metering, and odorization requirements
A town border station is the facility where gas transfers from a transmission pipeline to a local distribution system. It includes pressure regulation, metering, overpressure protection, heating, and odorization equipment designed per AGA, 49 CFR 192, and ASME B31.8.
Gas heaters at town border stations compensate for Joule-Thomson cooling that occurs during pressure reduction. Without heating, the gas temperature can drop below the hydrate formation point, causing ice-like blockages in regulators and downstream piping.
Per 49 CFR 192, town border stations require redundant overpressure protection including a monitor regulator and relief valve. The relief valve must handle the full regulator failure flow to prevent exceeding the downstream distribution system MAOP.
49 CFR 192.625 requires gas in distribution systems to contain odorant (typically mercaptan) at a level detectable at one-fifth of the lower explosive limit. The TBS design calculator checks whether odorant injection is needed based on the gas source and downstream requirements.