BLOCK VALVES - CLOSURE SWIFTNESS
8 MINUTES IS CRUCIAL
ONLY EVERY 20 MILES BECAUSE OF LOW POPULATION -
this means that 20 MILES of METHANE would be released.
There are NO environmental stations - NOT required.
The timeliness of manually shutting off the valves after a natural gas
release is crucial.
The swiftness of leak detection and pipeline shutdown capabilities
criteria is under or over an eight minute response time by firefighters
is crucial.
release is crucial.
The swiftness of leak detection and pipeline shutdown capabilities
criteria is under or over an eight minute response time by firefighters
is crucial.
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This procedure is called “block valve closure swiftness”
by the PHMSA involving the installation of both :
automatic shutoff valves (ASVs)
remote control valves (RCVs).
by the PHMSA involving the installation of both :
automatic shutoff valves (ASVs)
remote control valves (RCVs).
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Dominion Transmission refers to these as “Redundant Saftey Devices.”
Source: PHMSA
PHSMA
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“Gas transmission pipelines are currently required to incorporate sectionalizing block
valves at intervals that vary depending on population density.
valves at intervals that vary depending on population density.
These block valves are not required to be remotely operable or to operate
automatically in the event of an unexpected reduction in pressure
(e.g. from a pipeline rupture).
However, pipeline operators are required to conduct risk assessments of
automatically in the event of an unexpected reduction in pressure
(e.g. from a pipeline rupture).
However, pipeline operators are required to conduct risk assessments of
their pipelines and take additional measures to mitigate the consequences
of a pipeline failure in a HCA. (High Consequence Area)
of a pipeline failure in a HCA. (High Consequence Area)
Such additional measures may include, but are not limited to, installing ASVs or RCVs.
Hazardous liquid pipeline operators are required to install block valves
at prescribed locations to facilitate isolation of pump stations,
breakout storage tanks, and lateral takeoffs and other points along the pipeline
near designated bodies of water and populated areas to minimize damage
and pollution from an accidental hazardous liquid discharge.
at prescribed locations to facilitate isolation of pump stations,
breakout storage tanks, and lateral takeoffs and other points along the pipeline
near designated bodies of water and populated areas to minimize damage
and pollution from an accidental hazardous liquid discharge.
In addition, operators are required to consider installing emergency flow restricting
devices such as check valves and RCVs on pipeline segments to protect a HCA
in the event of a hazardous liquid pipeline release. In making this
devices such as check valves and RCVs on pipeline segments to protect a HCA
in the event of a hazardous liquid pipeline release. In making this
determination, an operator must, at least, consider the swiftness of leak detection
and pipeline shut down capabilities and benefits expected by reducing the spill size.
and pipeline shut down capabilities and benefits expected by reducing the spill size.
Block valve closure within 8 minutes after the break can result in a potential cost
avoidance of at least $2,000,000 for 12 in. nominal diameter natural gas pipelines
and $8,000,000 for 42-in. nominal diameter natural gas pipelines depending
and $8,000,000 for 42-in. nominal diameter natural gas pipelines depending
on the configuration of buildings within the Class 3 HCA.
Delaying block valve closure by an additional 5 minutes can reduce the cost
avoidance by approximately 50%. In addition, block valve closure in 8 minutes
increases the time fire fighters are able to conduct effective fire fighting operations
within a distance of 1.5 times the PIR by approximately 15 minutes or more.
avoidance by approximately 50%. In addition, block valve closure in 8 minutes
increases the time fire fighters are able to conduct effective fire fighting operations
within a distance of 1.5 times the PIR by approximately 15 minutes or more.
Shutoff Valves on Hazardous Liquids and Natural Gas Pipelines with Respect
to Public and Environmental Safety Oct 2013
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