1、 Tentative Interim Amendment NFPA59A Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG) 2016 Edition Reference: Various TIA 16-1 (SC 15-12-4 / TIA Log #1187R) Note: Text of the TIA was issued and approved for incorporation into the document prior to printing. 1. Add ne
2、w entries to Subsection 2.3.12 to read as follows: EN14620-1 through 5, (2006) Design and manufacture of site built, vertical, cylindrical, flat-bottomed, steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 C and -165 C PARTS 1 5. CEB Bulletin 187 (1988
3、) Concrete Structures under Impact and Impulsive Loading. 2. Add new 3.3.4.3.3* and Annex to read as follows (renumber current 3.3.4.3.3 as 3.3.4.3.4): 3.3.4.3.3* Membrane Containment Tank System. A tank system consisting of a thin metal liquid barrier and load-bearing thermal insulation supported b
4、y a self-standing outer concrete container jointly forming an integrated composite tank structure designed to contain liquid and vapor during tank operation as well as LNG in the event of leakage from the liquid barrier, and where the vapor-containing roof of the outer container is either steel or c
5、oncrete configured such that the excess vapor caused by a spill of LNG from the liquid barrier will discharge through the relief valves. A.3.3.4.3.3 A membrane containment tank system consists of a thin metal liquid- and vapor-tight barrier resting against load-bearing thermal insulation and support
6、ed by a free-standing outer pre-stressed concrete container. In normal conditions, primary liquid and vapor containment is provided by a thin metallic barrier which is structurally supported via load-bearing insulation on an outer pre-stressed concrete container. Under these conditions primary vapor
7、 containment is provided by a thin metallic barrier which is connected to the metallic roof liner. In emergency conditions, the secondary liquid and vapor containment is provided by an outer pre-stressed concrete container and metallic roof liner. The outer container must be capable of both containi
8、ng the liquid product and controlling the vapor resulting from evaporation. In this instance the vapor generated from the leakage is discharged through pressure relief valves located in the roof. Vapor losses due to permeability through the outer pre-stressed concrete are acceptable while the wall i
9、s containing liquid in the event of leakage from the thin metal barrier and insulation system. The roof of the outer pre-stressed concrete container may be concrete or steel. Significant design issues arise at the monolithic base-to-wall connection due to the mechanical restraint offered by the base
10、. To mitigate these issues, a secondary liquid containment barrier inside the insulation system across the entire bottom and part of the wall in the vicinity of the base-to-wall joint is to be provided to protect and thermally isolate this area from the cold liquid and provide liquid-tightness. Othe
11、r alternatives of the monolithic base-to-wall are described in ACI376. 3.3.4.3.4* Single Containment Tank System. A single wall container or a double wall tank system in which only the self-supporting primary or inner container is designed to contain LNG. 3. Revise 5.3.1.1(4) to read as follows: 5.3
12、.1.1 Provisions shall be made to minimize the potential of accidental discharge of LNG at containers, pipelines containing LNG, and other equipment such that a discharge from any of these does not endanger adjoining property or important process equipment and structures or reach waterways. LNG conta
13、iners shall be provided with one of the following methods to contain any release: (1) An impounding area surrounding the container(s) that is formed by a natural barrier, dike, impounding wall, or combination thereof complying with 5.3.2 and 5.3.3 (2) An impounding area formed by a natural barrier,
14、dike, excavation, impounding wall, or combination thereof complying with 5.3.2 and 5.3.3, plus a natural or man-made drainage system surrounding the container(s) that complies with 5.3.2 and 5.3.3 (3) Where the container is constructed below or partially below the surrounding grade, an impounding ar
15、ea formed by excavation complying with 5.3.2 and 5.3.3 (4) Secondary containment as required for double, or full, or membrane containment tank systems complying with 5.3.2 and 5.3.3. 4. Revise 5.3.2.5* and Annex to read as follows: 5.3.2.5* Dikes and impounding walls shall meet the following require
16、ments: (1) Dikes, impounding walls, drainage systems, and any penetrations thereof shall be designed to withstand the full hydrostatic head of impounded LNG or flammable refrigerant, the effect of rapid cooling to the temperature of the liquid to be confined, any anticipated fire exposure, and natur
17、al forces, such as earthquakes, wind, and rain. (2) Where the outer shell of a tank system complies with the requirements of 5.3.1.1, the dike shall be either the outer shell or as specified in 5.3.1.1. A.5.3.2.5 Section 7.2.1.1 requires compliance with API 625. API 625 paragraph 5.6 requires the se
18、lection of storage concept to be based on a risk assessment. API 625 Annex C discusses implications of a release of liquid from the primary liquid container and provides specific discussion related to each containment type. API 625 Annex D provides guidance for selection of storage concepts as part
19、of the risk assessment including external and internal events and hazards to be evaluated. Paragraph D.3.2.2 discusses the possibility of sudden failure of the inner tank and advises “if extra protection from brittle fracture” (or unabated ductile crack propagation) “is desired, the general practice
20、 is to increase the” primary container toughness. Available materials meeting the required specifications of API 620 Appendix Q (and this standard) for LNG service are considered to have crack-arrest properties at LNG service temperature and stress levels. Therefore, rapid failure of a steel primary
21、 container meeting this standard is not considered credible. In membrane containment tank systems, brittle fracture of membrane material is typically not a pertinent hazard for membrane tanks. However, other hazards based on a risk assessment should be considered. 5. Revise 5.3.2.7 to read as follow
22、s: 5.3.2.7 Double, full, and membrane containment tank systems shall be designed and constructed such that in the case of a fire in an adjacent tank, the secondary container shall retain sufficient structural integrity to prevent collapse, which can cause damage to and leakage from the primary conta
23、iner. 6. Revise 5.3.2.8 to read as follows: 5.3.2.8 Double, full, and membrane containment tank systems shall have no pipe penetrations below the liquid level. 7. Revise 5.3.4.2 and add new 5.3.4.2.1 to read as follows: 5.3.4.2 Double, full, and membrane containment tank systems of greater than 70,0
24、00 gal (265 m3) water capacity shall be separated from adjacent LNG storage containers such that a fire in an adjacent single or double containment impoundment or from a design spill will not cause loss of containment from adjacent containers. This shall be accomplished by ensuring that no part of t
25、he adjacent storage container roof, walls, or its impoundment structure reaches a temperature at which the strength of the material of the container roof, wall, or its impoundment is reduced to a level where the LNG tank, roof, or impoundment loses its structural integrity. 5.3.4.2.1 The outer concr
26、ete container shall be designed for the external fire in accordance with ACI 376 unless fire protection measures are provided. The outer tank thermal analysis shall be performed to determine temperature distribution for the heat flux and duration of exposure as specified in the fire risk assessment
27、within API 625. (1) The applicable load components and the ultimate state load factors for the fire load combinations shall be in accordance with ACI 376 Table 7.3. For membrane tanks, an additional liquid pressure load in accordance with ACI 376 Table 7.2 shall be included. (2) The design of the ou
28、ter concrete container shall take into account the following factors: (a) Reduction in the wall post-tensioning due to the difference in the coefficient thermal expansion of post-tensioning steel and wall concrete at the temperature to which the post-tensioning steel is exposed. The effects of the c
29、oncrete aggregate type on the concrete coefficient thermal expansion shall be considered; (b) Reduction in strength and modulus of elasticity of the outer tank concrete, reinforcing and post-tensioning steel due to elevated temperature; (c) Reduction in the wall post-tensioning due to pre-stressing
30、steel softening and relaxation at elevated temperature; (3) The concrete wall, including the wall concrete mix, shall be designed to avoid explosive spalling. 8. Revise 7.2.1.1 to read as follows: 7.2.1.1 Storage tank systems shall comply with the requirements of API 625, Tank Systems for Refrigerat
31、ed Liquefied Gas Storage, including membrane containment tank systems, and the additional provisions of this chapter. The API 625 risk assessment shall be approved by the AHJ. 9. Add new 7.2.1.4 and 7.2.1.5 and renumber current 7.2.1.4 to read as follows: 7.2.1.4 The metallic membrane, load-bearing
32、insulation, and the outer container moisture barrier specific to the membrane tank system shall comply with EN 14620 parts 1-5 for material selection, design, installation, examination, and testing and further requirements of 7.4. All other components of the membrane tank system shall comply with AP
33、I625, API620, ACI376 and additional requirements in Section 7.4. 7.2.1.5 All the membrane system components, including insulation, primary membrane, and the secondary barrier of the thermal protection system, shall be designed in such a way that they can withstand all possible static and dynamic act
34、ions throughout the tank lifetime. 7.2.1.46 Should any conflict exist between the above requirements, the most stringent requirement shall apply. 10. Revise 7.3.1.2 (A) to read as follows: 7.3.1.2 All piping that is a part of an LNG tank system shall comply with requirements in this chapter and requ
35、irements within API 625. (A) Tank system piping shall include all piping internal to the container, within insulation spaces and within void spaces, external piping attached or connected to the container up to the first circumferential external joint of the piping, and external piping serving only t
36、ank instrumentation (including tank pressure relief valves). All liquid piping with a source of external line pressure shall be designed for the external line relief valve setting but not less than 50 psi (345 kPa). Double, full, and membrane containment tank systems shall have no pipe penetrations
37、below the liquid level 11. Revise 7.3.3.2, 7.3.3.2(A), and 7.3.3.2(C) and add new (D) to read as follows: 7.3.3.2 The space between the inner container and the outer container shall contain insulation that is compatible with LNG and natural gas and that is noncombustible as installed for normal serv
38、ice and abnormal conditions. (A) A fire external to the outer tank shall not cause a reduction to the internal containment system performance due to damage to any component of the insulation systems. (B) The load-bearing bottom insulation shall be designed and installed so that cracking from thermal
39、 and mechanical stresses does not jeopardize the integrity of the container. (C) For tank systems other than membrane containment tank system, only materials used between the inner and outer tank bottoms (floors) shall not be required to meet the combustibility requirements, where the material and t
40、he design of the installation comply with all of the following: (1) The flame spread index of the material shall not exceed 25, and the material shall not support continued progressive combustion in air. (2) The material shall be of such composition that surfaces that would be exposed by cutting thr
41、ough the material on any plane shall have a flame spread index not greater than 25 and shall not support continued progressive combustion. (3) It shall be shown by test that the combustion properties of the material do not increase significantly as a result of long-term exposure to LNG or natural ga
42、s at the anticipated service pressure and temperature. (4) The materials in the installed condition shall be demonstrated to be capable of being purged of natural gas. (5) The natural gas remaining after purging shall not be significant and shall not increase the combustibility of the material. (D)
43、For membrane containment tank systems, the insulation system block shall include a non-foam cover (underneath the primary membrane) and shall include a welding thermal protection system in order to withstand all heat from welding during installation and during maintenance, if any. 12. Add a new 7.4.
44、2.3 to read as follows: 7.4.2.3 For membrane containment tank systems, weld procedure and production weld testing shall comply with EN14620 part 2 and the following requirements: 7.4.2.3.1 Qualification of Welders. All personnel associated with the welding fabrication of the membrane system shall be
45、 qualified by the manufacturer per an agreed upon schedule between the purchaser, the AHJ, and the fabricator. All records shall be available for review. 7.4.2.3.2 Inspection. 100% of all welding shall be visually examined for workmanship and conformance to the fabrication requirements. Bead placeme
46、nt and consistency shall be, at a minimum, documented by digital means for review by supervisory personnel. The personnel performing this visual inspection shall be qualified to an accepted standard for this inspection work. Upon cooldown of the welds to room temperature, provisions shall be made to
47、 perform a penetrant inspection (PT) of at least 5% of each weld type each day. The selection factors include orientation, welding direction, and complexity of welding being performed. a) All profiles and configurations of welds shall be subjected to this 5% requirement. The selection of this 5% sam
48、ple shall be agreed upon by the fabricator, customers representative, and the AHJ. b) The acceptance standard for this inspection technique shall be agreed upon by all parties. c) Any indication of a leak requires an additional 5% penetrant inspection of the total distance welded by each welder. Ins
49、pection after completion of membrane represents the last step prior to the cooldown of the tank to service temperature. After completion of the membrane, a leakage test shall be performed. Leakage shall be determined as agreed upon by the fabricator and customer. Tracer gas for this leak test shall be in accordance with approved procedure. All areas where leakage exceeds limit shall be repaired and inspected per 7.4.2.3.2, and the manufacturers approved procedure. In parallel, mechanical stress testing of the welding joints shall be performed by applying 3 cycles from atmospheri
