PREN 13941 : DRAFT 2009

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions, units and symbols
   3.1 Terms and definitions
   3.2 Units and symbols
4 General considerations for system design
   4.1 General requirements
   4.2 Service life
   4.3 Preliminary investigations
   4.4 Determination of project class
   4.5 Design documentation
5 Components and materials
   5.1 Basic requirements
   5.2 Steel pipe components
   5.3 Polyurethane foam insulation
   5.4 PE casing
   5.5 Expansion cushions
   5.6 Valves and accessories
6 Actions and limit states
   6.1 General
   6.2 Simplified analysis procedure
   6.3 Actions
   6.4 Limit states
7 Installation
   7.1 General
   7.2 Transportation and storage
   7.3 Excavation of pipe trench
   7.4 Installation of pipes and components
   7.5 Welding of the steel pipe and testing of the
        steel welds
   7.6 Strength pressure test and leak tightness test
   7.7 Assembly of casing pipes, joint installation
        and site insulation
   7.8 Backfilling of trench
   7.9 Pipe bends and other components
   7.10 Setting into operation
   7.11 Special constructions
   7.12 Construction work during the operation stage
Annex A (normative) - Design of piping components under
        internal pressure
   A.1 General
   A.2 Symbols
   A.3 Straight pipe and bends
        A.3.1 Straight pipes
        A.3.2 Bends
   A.4 Tees and branch connections
        A.4.1 General aspects and limitations
        A.4.2 Reinforcement
   A.5 Reducers and extensions
        A.5.1 General
        A.5.2 Minimum wall thickness of the cone
        A.5.3 Offset reducers
   A.6 Dished ends
        A.6.1 General
        A.6.2 Minimum required wall thickness for internal
              pressure
        A.6.3 Straight cylindrical shells
Annex B (informative) - Geotechnics and pipe-soil interaction
   B.1 Scope
        B.1.1 General
        B.1.2 General requirements
   B.2 Symbols and units
   B.3 Soil parameters for global analysis (pipe-soil interaction)
        B.3.1 Modelling pipe-soil interaction
        B.3.2 Pipe to soil friction (axial)
        B.3.3 Coefficient of horizontal soil reaction (lateral)
        B.3.4 Combined stiffness of PUR foam, expansion cushions
              and soil
   B.4 Characteristic values for soil loads and soil parameters
        B.4.1 General
        B.4.2 Soil mechanics study
   B.5 Specific requirements for stability
        B.5.1 General
        B.5.2 Vertical stability
        B.5.3 Horizontal stability
   B.6 Specific requirements for parallel excavations
        B.6.1 General
        B.6.2 Reduced friction
   B.7 Requirements for soft soils and settlement areas
        B.7.1 General
        B.7.2 Differential settlements
   B.8 Ovalization and circumferential stresses from top load
        B.8.1 Traffic load
        B.8.2 Stresses and ovalization from top load
        B.8.3 Deflection
Annex C (informative) - Global- and cross sectional analysis
   C.1 General
   C.2 Symbols
   C.3 Survey of limit states for steel
   C.4 Locations to be assessed
        C.4.1 Components to be considered
        C.4.2 Areas to be considered
   C.5 Actions
        C.5.1 General
        C.5.2 Action cycles
   C.6 Global analysis
        C.6.1 General
        C.6.2 Flexibility
        C.6.3 Boundary conditions
        C.6.4 Boundary conditions for pipe systems with single
              use compensators (SUC's)
   C.7 Calculation of stresses
        C.7.1 General
        C.7.2 Simplified procedure
        C.7.3 Cross section analyses, steel
        C.7.4 Straight pipes
        C.7.5 Bends
        C.7.6 Tees
        C.7.7 Other components
        C.7.8 PUR foam and PE casing
   C.8 Fatigue analysis
        C.8.1 Fatigue strength data
        C.8.2 Fatigue strength data, detailed design
        C.8.3 Design fatigue lives
   C.9 Further actions
Annex D (informative) - Calculation of heat losses
   D.1 General
   D.2 Heat loss per pipe pair
   D.3 Insulance of the soil
   D.4 Insulance of the insulation material
   D.5 Insulance of the heat exchange between flow and return
        pipe
Bibliography

Describes rules for design, calculation and installation for preinsulated bonded pipe systems for buried hot water distribution and transmission networks with pipe assemblies in accordance with EN 253, for continuous operation with hot water at various temperatures up to 120 degree C and occasionally with peak temperatures up to 140 degree C and maximum internal pressure 25 bar (overpressure).