Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1 Directives for standardization - Part 1: Structure and drafting of standards.
This standard was proposed by and is under the jurisdiction of SAC/TC 355 Subcommittee on Liquefied Natural Gas of National Technical Committee on Petroleum and Gas of Standardization Administration of China.
Specification for insulation design, construction and acceptance of cryogenic piping
1 Scope
This standard is applicable to the industrial piping with an external surface temperatures of -196℃ to 0℃ for constructed, extended or renovated projects.
This standard is not applicable to the piping with internal thermal insulation lining and special requirements (nuclear radiation devices, aviation industry and aerospace industry, etc.) and long-distance transmission piping.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1036-2008 Test method for coefficient of linear thermal expansion of plastics between -30℃ and 30℃ with a vitreous silica dilatometer
GB/T 2406.2 Plastics - Determination of burning behaviour by oxygen index - Part 2: Ambient-temperature test
GB/T 3280 Cold rolled stainless steel plate, sheet and strip
GB/T 3880.1 Wrought aluminium and aluminium alloy plates, sheets and strips for general engineering - Part 1: Technical conditions of delivery
GB/T 4339-2008 Test methods for thermal expansion characteristic parameters of metallic materials
GB/T 5486 Test methods for inorganic rigid thermal insulation
GB/T 6343 Cellular plastics and rubbers - Determination of apparent density
GB/T 7320 Refractories - Determination of thermal expansion
GB 8624 Classification for burning behavior of building materials and products
GB/T 8810 Determination of water absorption of rigid cellular plastics
GB/T 8813 Rigid cellular plastics - Determination of compression properties
GB/T 10294 Thermal insulation - Determination of steady-state thermal resistance and related properties - Guarded hot plate apparatus
GB/T 10295 Thermal insulation - Determination of steady-state thermal resistance and related properties - Heat flow meter apparatus
GB/T 10799 Rigid cellular plastics - Determination of the volume percentage of open cells and of closed cells
GB/T 14978 Continuously hot-dip aluminum-zinc alloy coated steel sheet and strip
GB/T 17146 Test methods for water vapour transmission properties of building materials and products
GB/T 17393 Specification for thermal insulation for use in contact with austenitic stainless steel
GB/T 25997-2010 Polyisocyanurate products for thermal insulation
GB 50185 Code for acceptance of construction quality of industrial equipment and pipeline insulation engineering
GB 50264 Code for design of industrial equipment and pipeline insulation engineering
GBZ 1 Hygienic standards for the design of industrial enterprises
JC/T 618-2005 Method of chemical analysis of thermal insulation materials for leachable chloride fluoride silicate and sodium ions
JC/T 647 Cellular glass product for thermal insulation
SY/T 7350-2016 Specification of coating and cold insulation for low temperature piping and equipment
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
insulation
measure taken to add insulation layer on the external surfaces of the piping and its accessories in order to reduce the heat dissipation from the piping and its accessories to the surrounding environment, or conversely, reduce the heat transfer from the surrounding environment to the inside of the piping and its accessories
3.1.2
insulation system
piping auxiliary system used to reduce heat exchange between industrial piping and the outside world, which is a complex with a complete structure consisting of an insulation layer, a vapor barrier and a cladding
3.1.3
insulation layer
insulation materials and their products which play a major role in maintaining the stability of medium temperature
3.1.4
vapor barrier
structural layer to prevent vapor from transferring
3.1.5
cladding
external protective structure to protect the thermal insulation layer and vapor barrier against external damage
3.1.6
fastener
members for fixing the insulation layer and cladding, including bolts, nuts, pins, hook nails, self-locking plates, hoop rings and straps, loose collars, fixed collars, etc.
3.1.7
supporting elements
members for supporting the thermal insulation layer and cladding, including brackets, support rings and support plates, etc.
3.1.8
circumferential joint
joint perpendicular to the axis of piping, which also refers to transverse joint and horizontal joint of square equipment
3.1.9
longitudinal joint
joint parallel to the axis of piping
3.1.10
rigid insulation
insulation which can basically keep its original state when in use, has a compressibility of less than 6% and does not bend under a load of 2×10-3
3.1.11
semi-rigid insulation
insulation which has a compressibility of 6%~30% under a load of 2×10-3MPa, and can restore its original shape when being bent by less than 90°
3.1.12
soft insulation
insulation which has a compressibility of 30% under a load of 2×10-3MPa, and can be bent by more than 90° without damage
3.1.13
expansion joint
clearance arranged in the insulation structure to adapt to the expansion and contraction of the insulation layer due to temperature change
3.1.14
vapor stop
structure which is arranged at both ends of the insulation structure and used for preventing water vapor from propagating longitudinally along the piping
3.1.15
secondary vapor barrier
vapor barrier arranged on the outer wall of the secondary outer layer of the multi-layer insulation layer structure
3.2 Symbols
For the purposes of this document, the following symbols apply.
T?——the temperature of the external surface of the piping;
Ta——the environment temperature;
Td——the dew point temperature;
ts——the external surface temperature of insulation layer;
Tl——the temperature of the external surface of the inner insulation layer;
￠——the relative humidity;
αs——the surface heat transfer coefficient of insulation structure;
Pc——the cooling price;
[Q]——the maximum allowable cold loss per unit of surface area of insulation layer, W/m2;
[q]——the maximum allowable cold loss per meter of piping length, W/m;
D?——the outer diameter of piping;
D?——the outer diameter of inner insulation layer;
D2——the outer diameter of outer insulation layer;
λ——the heat conductivity coefficient of insulation material at average temperature;
λ1——the heat conductivity coefficient of insulation material on the inner side;
λ2——the heat conductivity coefficient of insulation material on the outer side;
δ——the thickness of insulation layer (total thickness for double-layer insulation);
δ1——the thickness of inner insulation layer;
δ2——the thickness of outer insulation layer;
K——the insulation thickness correction coefficient;
PE——the energy price (cooling price);
t——the annual operating time;
PT——the unit cost of insulation structure;
S——the annual amortization rate of investment in insulation engineering.
4 Insulation structure
4.1 General
The insulation system structure shall not be damaged by its own load or accidental load.
4.2 Insulation layer
4.2.1 The fireproof performance of the insulation system shall meet the fireproof requirements of its insulation piping, and inorganic incombustible materials should be selected as insulation materials for piping with high fire risk.
4.2.2 For piping with alternating cold and hot operating temperatures, the materials of the insulation layer shall meet the requirements for use in high-temperature and low-temperature areas.
4.2.3 The insulation layer shall be tied and fixed with pressure-sensitive reinforced glass fiber tape or stainless steel tape, and hook nail structure shall not be used.
4.2.4 Detachable heat insulation structure should be adopted for the parts with disassembly requirements.
4.2.5 The bearing parts of piping supports and hangers shall be provided with rigid insulation cushion blocks, and the strength of the cushion blocks shall meet the bearing requirements.
4.2.6 Piping trunnions, lifting lugs, instrument piping sockets and other accessories shall be insulated. The thickness of the insulation layer shall not be less than 1/2 that of the connected piping and not less than 40 mm, and the length of the insulation layer shall not be less than 4 times of the thickness of the insulation layer or the insulation layer shall cover the cushion block.
4.2.7 The materials of fasteners and supporting elements of the insulation system should match the piping materials, otherwise, rigid insulation spacers shall be set.
4.2.8 The supporting elements of insulation layer shall be of the structural form with small cold bridge section. The insulation layer at the pipe-clamp bearing ring shall cover the end of the bolt hole.
4.2.9 The position of the insulation layer supporting element shall be away from the valve, flange and piping weld, and the supporting element of the vertical piping shall be located above the valve and flange, and its position shall not affect the pipe disassembly.
4.2.10 The insulation layer of elbow, tee, reducer and other pipe fittings and special parts of piping should be prefabricated.
4.2.11 The insulation structure of valves and flanges should be made of rigid insulation prefabricated profiles.
4.2.12 When the thickness of the insulation layer is greater than 80 mm, the rigid insulation shall be constructed in two or more layers.
4.2.13 The expansion joints shall be set for the insulation layer according to the following requirements:
a) The width of expansion joint should be 20 mm ~ 25 mm.
b) The expansion joint spacing should not be greater than 5 m for piping at a temperature of -101℃~1℃ or should not be greater than 3.5 m for piping with a temperature below -101℃.
c) Expansion joints of insulation layer should be tightly filled with low-temperature glass wool and shall be sealed with butyl rubber.
4.3 Vapor barrier
4.3.1 A vapor barrier shall be set on the external surface of the insulation layer.
4.3.2 Secondary vapor barrier should be set at the stratification of insulation layer structure.
Foreword i
1 Scope
2 Normative references
3 Terms, definitions and symbols
3.1 Terms and definitions
3.2 Symbols
4 Insulation structure
4.1 General
4.2 Insulation layer
4.3 Vapor barrier
4.4 Cladding
5 Insulation calculation
5.1 General requirements
5.2 Calculation parameter selection
5.3 Calculation of cold loss
5.4 Thickness calculation of cylindrical insulation layers
5.5 Thickness calculation of planar insulation layer
6 Materials
6.1 Performances of insulation layer materials
6.2 Vapor barrier
6.3 Cladding
6.4 Other materials
6.5 Transportation, storage and custody of materials
7 Construction
7.1 General requirements
7.2 Construction conditions
7.3 Construction of prefabricated profiles
7.4 Construction of insulation layers of valves and flanges
7.5 Construction of vapor barrier
7.6 Construction of cladding
8 Acceptance
8.1 Material acceptance
8.2 Construction acceptance
8.3 Engineering acceptance
9 Engineering handover
10 Health, safety and environment (HSE)
Bibliography
