Section 460.20407. Sectionalizing block valves.

In addition to the requirements in 49 C.F.R. §192.179, which is adopted by reference in R 460.20606, an operator of pipeline facilities used in the transportation of sour gas shall comply with all of the following requirements for any portion of the pipeline that contains more than 10 pounds of H2S per mile, with the weight calculated according to the formula W=0.0933 (P) (V) (MW) (H) /T, where W=Weight of H2S in pounds per mile of pipe, P=Absolute pressure in pounds per square inch, V=Volume of one mile of pipe in cubic feet, mw=Molecular weight of natural gas, H=Percentage of H2S in the gas, and T=Temperature in degrees Rankine:

(a)     Sectionalizing block valves shall be installed and located so that each point on the pipeline is within 3 miles of a sectionalizing block valve with a block valve located at each end of the pipeline.

(b)     A pipeline shall incorporate block valve automation so that block valves will automatically   close  upon  the  registering   of  low  pressure readings.  The system shall

be designed to operate even in  the  event  of  a power failure or malfunction of electronic devices and shall be designed  to fail in a closed position.

(c)        A pipeline shall incorporate a supervisory control and data acquisitions (SCADA)  system that  complies  with  all  of  the   following provisions:

(i)     Is monitored by the operator to ensure appropriate   response  to emergencies.

(ii)         Is programmed to automatically close  block  valves   based  on operating data gathered at each metering site and at each automated block valve.

(iii)       Automatically closes the upstream and downstream sectionalizing block valves surrounding any sectionalizing block valve that is in an alarm condition.

(iv)      Allows the operator monitoring the SCADA system to close, but not open, any or all of the block valves and metering points.

(d)     H2S sensors shall be located at all sectionalizing block valve sites. The sensors shall provide a warning to the SCADA system at H2S levels of 10 ppm and shall close the block valve at H2S levels of 30 ppm.

(e)       Control valves shall be installed at appropriate locations at well sites or laterals to automatically shut off the flow of gas into the pipeline in the event of a line break or over pressure conditions.

History: 2003 AACS; 2009 AACS; 2010 AACS.