NEN EN 253 : 2009 + A2 2015

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Requirements
   4.1 General
   4.2 Steel service pipe
       4.2.1 Quality
       4.2.2 Diameter
       4.2.3 Wall thickness
       4.2.4 Surface condition
   4.3 Casing
       4.3.1 Material properties
       4.3.2 Casing properties
   4.4 Polyurethane rigid foam insulation (PUR)
       4.4.1 Composition
       4.4.2 Cell structure
       4.4.3 Foam density
       4.4.4 Compressive strength
       4.4.5 Water absorption at elevated temperature
   4.5 Pipe assembly
       4.5.1 Pipe ends
       4.5.2 Increase in diameter of the casing pipe
       4.5.3 Centre line deviation
       4.5.4 Expected life and long-term temperature resistance
       4.5.5 Thermal conductivity in unaged condition
       4.5.6 Impact resistance
       4.5.7 Creep behaviour
       4.5.8 Surface conditions at delivery
5 Test methods
   5.1 General
       5.1.1 Test specimens
   5.2 Casing
       5.2.1 Material density
       5.2.2 Dimensions
       5.2.3 Appearance and surface finish
       5.2.4 Heat reversion
       5.2.5 Long-term mechanical properties
       5.2.6 Constant load tensile test (CLT)
       5.2.7 Elongation at break
       5.2.9 Notched constant load test
   5.3 Polyurethane rigid foam insulation (PUR)
       5.3.1 Composition
       5.3.2 Cell structure
       5.3.3 Foam density
       5.3.4 Compressive strength
       5.3.5 Water absorption
   5.4 Pipe assembly
       5.4.1 Increase in diameter of the casing pipe
       5.4.2 Axial shear strength
       5.4.3 Tangential shear strength
       5.4.4 Shear strength of the pipe assembly after ageing
       5.4.5 Thermal conductivity
       5.4.6 Impact resistance
       5.4.7 Creep behaviour at 140 degrees C
6 Marking
   6.1 General
   6.2 Steel service pipe
   6.3 Casing
   6.4 Pipe assembly
Annexes
A (informative) Relation between actual continuous
     operating conditions and accelerated ageing test
     conditions
B (informative) Calculation of the minimum expected
     thermal life with operation at various temperatures
     with respect to PUR foam performance
C (normative) Calculated continuous operating temperature (CCOT)
    C.1 general
    C.2 Symbols
    C.3 Ageing and shear strength determinations
    C.4 Calculations
        C.4.1 Determination of the thermal life at different
              ageing temperatures
        C.4.2 Adoption to the Arrhenius relation
        C.4.3 Calculated continuous operating temperature, CCOT
D (informative) Guidelines for inspection and testing
    D.1 Manufacturer's type test
    D.2 Manufacturer's quality surveillance
    D.3 External inspection
    D.4 Manufacturer's responsibility
E (informative) Change of blowing agent and influence on
    thermochemical and thermomechanical properties of
    polyurethane rigid foam (PUR)
F (normative) Radial creep behaviour of the polyurethane
    foam (PUR)
G (normative) Thermal conductivity of pre-insulated pipes -
    Test procedure
    G.1 Scope
    G.2 Requirements
        G.2.1 Test specimen
        G.2.2 Operating temperature
        G.2.3 Types of apparatus
    G.3 Apparatus
        G.3.1 Guarded end apparatus
        G.3.2 Calibrated end apparatus
        G.3.3 Dimensions
        G.3.4 Heater pipe surface temperature
    G.4 Test specimens
        G.4.1 Conditioning
        G.4.2 Dimension measurement
        G.4.3 Surface temperature measurement
    G.5 Procedure
        G.5.1 Test length
        G.5.2 Diameter
        G.5.3 Thickness of casing
        G.5.4 Ambient requirements
        G.5.5 Test pipe temperature
        G.5.6 Power supply
        G.5.7 Axial heat loss
        G.5.8 Test period and stability
    G.6 Calculations
        G.6.1 Thermal conductivity
    G.7 Symbols and units
H (informative) National A-deviations
    H.1 Swedish national legislative deviations on steel
        service pipes
Bibliography

Defines requirements and test methods for straight lengths of prefabricated thermally insulated pipe-in-pipe assemblies for directly buried hot water networks, comprising a steel service pipe from DN 15 to DN 1200, rigid polyurethane foam insulation and an outer casing of polyethylene.