NEN EN 448 : 2015

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Requirements
   4.1 Steel parts
       4.1.1 Quality
       4.1.2 Wall thickness and diameter
       4.1.3 Bends
       4.1.4 T-pieces
       4.1.5 Reducers
       4.1.6 Anchors
       4.1.7 Fusion welding of steel fittings
       4.1.8 Surface condition
   4.2 Casing
   4.3 Polyurethane rigid foam insulation (PUR)
   4.4 Fitting assemblies
       4.4.1 Fitting ends
       4.4.2 Angle between casing segments of bend and
             minimum length
       4.4.3 Requirements of polyethylene welding
       4.4.4 Leak-tightness of the welded casing pipe
       4.4.5 Increase in diameter of the casing pipe
       4.4.6 Minimum insulation thickness in bends
       4.4.7 Tolerances of the main fitting dimensions
5 Test methods
   5.1 General
   5.2 Test specimens
   5.3 Steel parts
       5.3.1 Visual surface examination of welds
       5.3.2 Leak-tightness test with water
       5.3.3 Leak-tightness test with air
       5.3.4 Radiographic examination of butt welds
   5.4 Casing
   5.5 Polyurethane rigid foam insulation (PUR)
   5.6 Fitting assemblies
       5.6.1 Centre line deviation and angular deviation
       5.6.2 Visual examination of welds on casing pipes
       5.6.3 Bending test
       5.6.4 Increase in diameter of the casing pipe
       5.6.5 Minimum insulation thickness
       5.6.6 Leak-tightness of casing pipe fittings
6 Marking
   6.1 General
   6.2 Steel service pipe
   6.3 Casing
   6.4 Fitting assembly
Annexes
A (informative) Guidelines for inspection and testing
    A.1 Manufacturer's type test
    A.2 Manufacturer's quality surveillance
    A.3 External inspection
    A.4 Manufacturer's responsibility
B (informative) Procedures for polyethylene welding
    B.1 Introduction
    B.2 Requirements for site, machine and equipment
    B.3 Items
    B.4 Butt fusion welding
        B.4.1 Equipment
        B.4.2 Welding procedure
    B.5 Extrusion welding
        B.5.1 Equipment
        B.5.2 Welding procedure
Bibliography

Defines requirements and test methods for fittings of prefabricated thermally insulated pipe-in-pipe assemblies comprising a steel service fitting from DN 20 to DN 1200, rigid polyurethane foam insulation and an outer casing of polyethylene for use in directly buried hot water networks with preinsulated pipe assemblies in accordance with EN 253.