Interpretation Response #PI-79-020
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
SUBJECT: Request for Interpretation
FROM: Chief, Central Region, DMT-14
TO: Associate Director, Office of Pipeline Safety Regulation, DMT-30
THRU: Associate Director, Office of Operations & Enforcement, DMT-10
Attached is a piping schematic indicating pressure regulation within a gas system. The schematic includes the transmission lines from the point of purchase from an interstate transmission line and the mains. I would like to know at what stations telemetering or recording pressure gauges are required in accordance with §192.741(a). The regulation states that "each distribution system supplied by more than one district pressure regulating station must be equipped with telemetering or recording pressure gauges to indicate the gas pressure in the district."
The distribution system is supplied by an 8-inch diameter transmission line which haws been looped with a 4-inch transmission line as shown. These lines are operated at 172 psig and supply gas to regulator stations A and B. All of the regulating equipment enclosed by the dashed line is located at station B. All other regulating equipment shown is at separate locations within the system. The regulating stations are denoted by letters A through G.
The system consists of sections, or districts, operating at pressures of 60 psig, 25 psig, 15 psig, 8 psig, and 6 ounces. The maximum allowable operating pressures of these sections are the same as the operating pressures, since §192.619(a)(3) has been interpreted to apply to distribution piping.
As indicated by the diagram, the 15 psig segment of the system can be supplied by regulator stations C, D, and E. The 8 psig segment of the system can be supplied by stations G and F. The 25 psig segment can be supplied by stations A and B. The 6 ounce segment can be supplied by two different regulator settings within station B. It is the intent of §192.741(a) to require telemetering or pressure recording devices only when the entire distribution system is supplied by more than one regulator stations, or does it also apply to districts within one distribution system? Is each pressure district within this system a separate distribution system?
The operating, or set pressures of the regulators within station B are as denoted on the schematic. The other regulator stations are operated as follows:
Station A: Inlet pressure 175 psig. This regulator is set at 10 psig to augment gas supply in the 25 psig segment should the pressure in that area drop that low during periods of high consumption.
Station C: Inlet pressure 60 psig. Outlet pressure 15 psig.
Station D and E: Inlet pressure 25 psig. These two regulators are set to operate at 10 psig to augment gas supply to the 15 psig segment should the pressure in that area drop that low during periods of high consumption.
Stations G and F: Inlet pressure 25 psig. Outlet pressure 8 psig.
Additionally, does Part 192 require overpressure protection to be installed at regulator stations D, E, F, and G. The facilities were installed in the 1950's and the maximum allowable operating pressures have been based on §192.619(a)(3). This question has arisen because determining the pressure per §192.619(a)(3) is based on operating history, as is §192.619(a)(b).
If you have any questions in regard to the system or comments which you feel would help to clarify this matter, please don't hesitate to call.
Marshall W. Taylor, II
|§ 192.741||Pressure limiting and regulating stations: Telemetering or recording gauges|