CJJ/T 104-2014 1 General provisions
1.0.1 This specification is developed to standardize the design, construction, acceptance and operational maintenance of directly buried steam heating pipeline in city, unify technical requirements, ensure project quality, and achieve economic rationality, safety and applicability.
1.0.2 This specification is applicable to the design, construction, acceptance and operational maintenance of directly-buried steel outer protective steam heat preservation pipes with working pressure less than or equal to 2.5 MPa and temperature less than or equal to 350°C.
1.0.3 In addition to this specification, the directly buried steam pipe project in seismic, collapsible loess, expansive soil and other regions shall also meet the relevant provisions of the current national standards GB 50032 Code for seismic design of outdoor water supply sewerage gas and heating engineering, GB 50025 Code for building construction in collapsible loess regions and GB 50112 Technical code for building in expansive soil regions.
1.0.4 The design, construction, acceptance and operational maintenance of directly buried steam pipes shall comply with the current national standards in addition to this specification.
2 Terms
2.0.1 directly buried steam pipe
prefabricated heat preservation pipe directly buried in soil layer for transporting steam
2.0.2 working pipe
steel pipe for transporting steam in the directly buried steam heat preservation pipe construction
2.0.3 outer protective pipe
bushing with sufficient mechanical strength and reliable waterproof performance outside the insulating layer to resist the damage and influence of external force and environment on insulating materials
2.0.4 antiseptic layer
corrosion-resistant material layer coated tightly on the surface of an outer protective steel pipe against corrosion
2.0.5 heat preservation pipe patch
treatment of interface of insulating layer, outer protective pipe and antiseptic layer at the junction of directly buried steam pipe
2.0.6 casing drain
conduit for discharging water vapor between the working pipe and the outer protective pipe
2.0.7 inside fixed support
accessories of pipeline that prevent relative displacement between working pipe and outer protective pipe
2.0.8 outside fixed support
accessories of pipeline that prevent relative displacement between outer protective pipe and fixed pier
2.0.9 inside and outside fixed support
accessories of pipeline that prevent relative displacement among working pipe, outer protective pipe and fixed pier
2.0.10 radiation heat insulation layer
polished metallic aluminum foil layer arranged on the wall of the air layer in the insulation construction with air layer, which uses its low surface emissivity and high reflectivity to reduce the surface radiation heat transfer and improve the thermal insulation effect
2.0.11 vacuumize
technological process enabling a certain vacuum degree between the working pipe and the outer protective pipe
3 Arrangement and installation of pipes
3.1 Arrangement of pipes
3.1.1 The arrangement of directly buried steam pipe shall meet the relevant provisions of the current professional standard CJJ 34 Design code for city heating network.
3.1.2 The minimum clear distance between directly buried steam pipe and other facilities shall be as specified in Table 3.1.2; effective protective measures shall be taken, if the clear distance in the table cannot be met or there are special requirements for other facilities.
Table 3.1.2 Minimum clear distance between directly buried steam pipe and other facilities
Facility name Minimum horizontal clear distance (m) Minimum vertical clear distance (m)
Water supply and drainage pipe 1.5 0.15
Directly buried hot water pipe/condensate pipe 0.5 0.15
Blind drainage ditch 1.5 0.50
Gas pipe (steel pipe) ≤0.4MPa 1.0 0.15
>0.4MPa, ≤0.8MPa 1.5
>0.8MPa 2.0
Gas pipe (polyethylene pipe) ≤0.4MPa 1.0 0.50, gas pipe at the top
1.00, gas pipe at the bottom
>0.4MPa, ≤0.8MPa 1.5
>0.8MPa 2.0
Compressed air or CO2 pipe 1.0 0.15
Acetylene and oxygen pipe 1.5 0.25
Railway rail Outside of rail: 3.0 From rail bottom: 1.20
Steel rail of trolley Outside of rail: 2.0 From rail bottom: 1.00
Side slope feet of railway and highway subgrade or fringe of side ditch 1.0 —
Electric poles for communication, lighting or power lines up to 10kV 1.0 —
Foundation fringe of electricity pylon (35kV~220kV) 3.0 —
Pier (viaduct, trestle) 2.0 —
Foundation of bracket for overhead pipe 1.5 —
Metro tunnel structure 5.0 0.80
Pole-foundation of electric railway contact system 3.0 —
Arbors and shrubs 2.0 —
Building foundation 2.5
(Outer protective pipe≤400mm) —
3.0
(Outer protective pipe>400mm) —
Cable Ball lump of communication cable 1.0 0.15
Power and control cables ≤35kV 2.0 0.50
>35kV, ≤110kV 2.0 1.00
Note: When directly buried steam pipes are installed in parallel with cables, for cables with a voltage of 10 kV, the soil temperature around the cable shall not exceed the monthly average natural soil temperature by 10°C at any time of the year; for cables with a voltage of 35 kV to 110 kV, when the soil temperature around the cable does not exceed the monthly average natural soil temperature by 5°C, the clear distances listed in the table can be reduced accordingly.
3.1.3 When the directly buried steam pipe intersects with other underground pipelines, the horizontal clear distance between the pipeline accessories of the directly buried steam pipe and the intersection point should be greater than 3 m.
3.1.4 The minimum covering depth of directly buried steam pipe shall be as specified in Table 3.1.4. Otherwise, corresponding technical measures shall be taken to protect the pipes.
Foreword ii
1 General provisions
2 Terms
3 Arrangement and installation of pipes
3.1 Arrangement of pipes
3.2 Installation method
3.3 Material of pipes
4 Accessories of pipelines
4.1 Accessories and facilities of pipelines
4.2 Connecting of pipe fittings and pipes
5 Calculation of pipe strength and stress
5.1 Working pipe
5.2 Outer protective pipe
6 Insulation construction and insulating layer
6.1 General requirements
6.2 Insulation construction
6.3 Vacuum insulating layer
6.4 Insulation calculation
7 Outer protective pipe and anticorrosion
7.1 General requirements
7.2 Stiffness and stability of outer protective pipe
7.3 Anticorrosion of outer protective pipe
8 Construction and acceptance
8.1 General requirements
8.2 Pipe installation
8.3 Heat preservation pipe patch
8.4 Vacuum system installation
8.5 Pressure test, purging and trial operation
8.6 Construction and acceptance
9 Operation management
9.1 General requirements
9.2 Preparation before operation
9.3 Warming pipe
9.4 Operational maintenance
9.5 Operational stop
Annex A Monthly average of measured ground temperature (depth 0.0 m to 3.2 m) in major Chinese cities
Annex B Calculation of temperature field near directly buried steam pipe
Annex C Calculation of radial deformation of steel pipe
Explanation of wording in this specification
List of quoted standards
Explanation of provisions
