Louisiana Administrative Code
Title 43 - NATURAL RESOURCES
Part XIII - Office of Conservation-Pipeline Safety
Subpart 5 - Liquefied Natural Gas Facilities: Federal Safety Standards
Chapter 69 - Siting Requirements [49 CFR Part 193 Subpart B]
Section XIII-6959 - Flammable Vapor-Gas Dispersion Protection [49 CFR 193.2059]
Universal Citation: LA Admin Code XIII-6959
Current through Register Vol. 50, No. 9, September 20, 2024
A. Each LNG container and LNG transfer system must have a dispersion exclusion zone in accordance with sections 2.2.3.3 of NFPA-59A-2001 (incorporated by reference, see §6713) with the following exceptions.
1.
Flammable vapor-gas dispersion distances must be determined in accordance with
the model described in the GTI-04/0049, "LNG Vapor Dispersion Prediction with
the DEGADIS 2.1 Dense Gas Dispersion Model" (incorporated by reference, see
§6713). Alternatively, in order to account for additional cloud dilution which
may be caused by the complex flow patterns induced by tank and dike structure,
dispersion distances may be calculated in accordance with the model described
in the Gas Research Institute report GRI-96/0396.5 (incorporated by reference,
see §6713), "Evaluation of Mitigation Methods for Accidental LNG Releases.
Volume 5: Using FEM3A for LNG Accident Consequence Analyses". The use of
alternate models which take into account the same physical factors and have
been validated by experimental test data shall be permitted, subject to the
Commissioner's approval. [
49 CFR
193.2059(a)]
2. The following dispersion parameters must
be used in computing dispersion distances.
a.
Average gas concentration in air = 2.5 percent. [
49 CFR
193.2059(b)(1)]
b. Dispersion conditions are a combination of
those which result in longer predicted downwind dispersion distances than other
weather conditions at the site at least 90 percent of the time, based on
figures maintained by National Weather Service of the U.S. Department of
Commerce, or as an alternative where the model used gives longer distances at
lower wind speeds, Atmospheric Stability (Pasquill Class) F, wind speed = 4.5
miles per hour (2.01 meters/sec) at reference height of 10 meters, relative
humidity = 50.0 percent, and atmospheric temperature = average in the region. [
49 CFR
193.2059(b)(2)]
c. The elevation for contour (receptor)
output H = 0.5 meters. [
49 CFR
193.2059(b)(3)]
d. A surface roughness factor of 0.03 meters
shall be used. Higher values for the roughness factor may be used if it can be
shown that the terrain both upwind and downwind of the vapor cloud has dense
vegetation and that the vapor cloud height is more than ten times the height of
the obstacles encountered by the vapor cloud. [
49 CFR
193.2059(b)(4)]
3. The design spill shall be
determined in accordance with section 2.2.3.5 of NFPA-59A-2001 (incorporated by
reference, see §6713). [
49 CFR
193.2059(c)
]
AUTHORITY NOTE: Promulgated in accordance with R.S. 30:551.C.
Disclaimer: These regulations may not be the most recent version. Louisiana may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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