GB/T 39246-2020 in English

《GB/T 39246-2020高密度聚乙烯无缝外护管预制直埋保温管件》由TC455（全国城镇供热标准化技术委员会）归口，主管部门为住房和城乡建设部。

Prefabricated directly buried insulating fittings with seamless high density polyethylene casing pipe

1 Scope

This standard specifies the terms and definitions, product construction, requirements, test methods, inspection rules, as well as marking, transportation and storage of prefabricated directly buried insulating fittings with seamless high density polyethylene casing pipe.

This standard is applicable to the manufacturing and inspection of the prefabricated directly buried insulating fittings with seamless high density polyethylene casing pipe whose conveying medium temperature (long-term operating temperature) is not greater than 120°C and peak temperature is not greater than 130°C.

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 8923.1-2011 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous
GB/T 12459 Steel buttwelding pipe fittings - Types and parameter
GB/T 13401 Steel buttwelding pipe fittings - Technical specification
GB/T 18475-2001 Thermoplastics materials for pipes and fittings for pressure applications - Classification and designation - Overall service (design) coefficient
GB/T 29046 Test methods of technical specification for pre-insulated directly buried district heating pipes
GB/T 29047 Prefabricated directly buried insulating pipes and fittings with polyurethane foamed-plastics and high density polyethylene casing pipes
GB 50236-2011 Code for construction of field equipment, industrial pipe welding engineering
CJJ/T 254 Technical specification for leakage surveillance system of directly buried heating pipe
NB/T 47013.2-2015 Nondestructive testing of pressure equipments - Part 2: Radiographic testing
NB/T 47013.3-2015 Nondestructive testing of pressure equipment - Part 3: Ultrasonic testing
NB/T 47014 Welding procedure qualification for pressure equipment
SY/T 5257 Steel bends for oil and gas transmission

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1
seamless high density polyethylene casing pipe
generic term for seamless casing elbow, seamless casing bend, seamless casing T-shaped tee, seamless casing reducer, etc., which are formed by extrusion or pulling from high density polyethylene raw materials

3.2
reinforced weld
butt weld of polyethylene casing branch pipe of T-shaped tee using an electric fusion welding tape sleeve

3.3
determination of environmental stress cracking
capability of polyethylene specimens to withstand sustained static tensile loads when they are immersed in a surfactant solution at a specific temperature

4 Product structure

4.1 The prefabricated directly buried insulating fittings with seamless high density polyethylene casing pipe shall be of a bonded insulation structure in which steel fitting, insulating layer and seamless casing fitting are closely bonded, and guiding holder and signal line may be set in the insulating layer.

4.2 The schematic diagram of product structure is shown in Figure 1.

Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Product structure
5 Requirements
5.1 Steel fitting
5.2 Casing fittings
5.3 Insulating layer
5.4 Insulating fittings
6 Test methods
7 Inspection rules
7.1 Inspection classification
7.2 End-of-manufacturing inspection
7.3 Type inspection
8 Marking, transportation and storage
8.1 Marking
8.2 Transportation
8.3 Storage
Annex A (Normative) Dimensions of T-shaped insulating tee