This standard defines the terms and definitions of malleable cast iron pipe fittings (hereinafter referred to as "pipe fittings"), establishes the product classification and marking of pipe fittings, specifies the technical requirements such as materials, design, appearance and performance of pipe fittings, and describes the corresponding test methods, inspection rules, marking, packaging, transportation and storage, etc.
This document is applicable to the design, manufacture and acceptance of pipe fittings for general pipeline connections with a maximum working pressure of 2.5MPa, nominal dimensions (DN) 6 to (DN) 150, operating temperatures ranging from -20 to 300°C, and working media such as water, oil, air, gas and steam.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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 192 General purpose metric screw threads - Basic profile
GB/T 193 General purpose metric screw threads - General plan
GB/T 196 General purpose metric screw threads - Basic dimensions
GB/T 197 General purpose metric screw threads - Tolerances
GB/T 2828.1 Sampling procedures for inspection by attributes - Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
GB/T 2829-2002 Sampling procedures and tables for periodic inspection by attributes (Apply to inspection of process stability)
GB/T 4956 Non-magnetic coatings on magnetic substrates - Measurement of coating thickness - Magnetic method
GB/T 7306.1 Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads - Part 1: Parallel internal and taper external threads
GB/T 7306.2 Pipe threads with 55 degree thread angle where pressure-tight joints are made on the threads - Part 2: Taper internal and external threads
GB/T 7307 Pipe threads with 55 degree thread angle where pressure-tight joints are not made on the threads
GB/T 9440 Malleable iron castings
GB/T 10125 Corrosion tests in artificial atmospheres - Salt spray tests
GB/T 12689 (all parts) The methods for chemical analysis of zinc and zinc alloys
GB/T 13825 Metallic coatings - Hot dip galvanized coatings on ferrous materials - Gravimetric determination of the mass per unit area
GB/T 36488 Determination of polycyclic aromatic hydrocarbons in coatings
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
fitting
product for connecting of one or more parts
3.2
broad brim
throat
a structure where the ends of pipe fittings completely cover the exposed threads of the pipeline is adopted to effectively protect the exposed threads from corrosion and extend the overall service life of the pipeline system
3.3
reinforced edge
additional structure on the outside diameter of an internally threaded fitting in the form of square edge or round edge (see Figure 1)
3.4
outlet
internally or externally threaded end of a pipe fitting, which connects with a tube, fitting or other component
Note: The thread of sealing pipe shall meet the requirements of GB/T 7306.1 or GB/T 7306.2;
3.5
main pipe
Two principal axially aligned outlets of a tee or cross.
3.6
branch pipe
Side outlet(s) of a tee or cross.
3.7
chamfer
conical portion at the entrance of a thread to assist assembly and prevent damage to the start of the thread
3.8
face-to-face dimension
distance between the two parallel faces of axially aligned outlets of a fitting
3.9
face-to-centre dimension
distance between the face of an outlet and the intersection point of central axis of an angularly disposed outlet.
3.10
malleability
flattening rate
plastic deformation capacity exhibited by malleable cast iron pipe fittings when subjected to continuous pressure along a direction perpendicular to the longitudinal axis under certain conditions
4 Product classification
4.1 Classification according to surface status
Pipe fittings can be classified into the following two types according to the surface status:
— black pipe fittings symbols: Fe;
— galvanized pipe fittings symbols: Zn.
4.2 Classification according to structural type
4.2.1 The types and symbols of pipe fittings are listed in Table 1. These symbols are related to pipeline identification and can be used for marking (see 4.4.1).
4.2.2 When U1, U2, UA1 and UA2 are used in flat seat unions, they shall be used in conjunction with the gaskets specified in B.24. The materials selected for the gaskets shall be suitable for the relevant requirements of the medium in the service environment.
4.3 Classification according to product type
Pipe fittings can be classified as follows according to the product type:
— Type I pipe fittings (see Annex A);
— Type II pipe fittings (see Annex B);
— Type III pipe fittings (see Annex C):
The applicable fields of product types are shown in Table 2.
4.4 Product designation
4.4.1 Designation contents
4.4.1.1 Marking items
When marking pipe fittings that comply with this document, the marking items shall include the following:
a) pipe fittings type (see Table 1);
b) executive standard No;
c) symbols (see Table 1);
d) pipe fitting sizes (see Annex A, Annex B, Annex C);
e) surface state (see 4.1);
f) design symbols (see 5.4.1).
4.4.1.2 Comparison table of pipe fitting sizes and nominal dimensions
The pipe fitting size (i.e., the thread size code) is the thread code at the outlet end of the marking that complies with GB/T 7306.1 and GB/T 7306.2 for pipe threads.
When marking in accordance with 4.4.1.1, the corresponding symbols and fitting sizes can be replaced by nominal sizes. The comparison between the pipe fitting sizes and nominal dimensions (DN) is shown in Table 3.
4.4.2 Additional remarks for designation
4.4.2.1 Pipe fittings with same diameter, namely dimensions at outlet are the same, are represented by same dimension.
4.4.2.2 Reducing fittings with two outlet are specified in decrescent sequence of outlet dimension (large outlet to small outlet).
4.4.2.3 Reducing fittings with more than two different dimension outlets are designated in accordance with the requirements of Figures 2 and 3. Type a is the default type, while type b needs to be indicated.
4.4.2.4 Reducing fittings with more than two outlets but with unchanged main pipe sizes are designated as follows:
a) tees B1 and E1 with equal outlets on the run and an increasing or decreasing outlet on the branch: specified by the size of the run followed by the size of the branch, for example 1 × 3/4 (see A.4, A.5,B.4, B.5 and B.10);
b) twin elbows reducing E2: the size of the large outlet is specified followed by the size of the two smaller outlets, for example, 1×1 (see B.13);
c) reducing crosses C1: the size of the largest run is specified followed by the size of the two smaller (but equal) branches, for example 1×1 (see A.7 and B.8).
4.4.3 Designation example
Example 1: Equal female elbow with pipe fitting size 2, black finish, design symbol A, designated as Elbow GB/T 3287 A1-2-Fe-A.
Example 2: Reducing tee with main pipe fitting size 2 and branch pipe fitting size 1, hot-dip zinc-coated, design symbol C, designated as Tee GB/T 3287 B1-2×1-ZN-C.
Example 3: Reducing tee with main pipe fitting sizes 1 and 3/4 and branch pipe fitting size 1/2, black finish, design symbols B and D, designated as Tee GB/T 3287 B1-1×1/2×3/4-Fe-B.
Example 4: Reducing tee with main pipe fitting sizes 1 and 3/4 and branch pipe fitting size 1/2, black finish, design symbols B and D, designated as Tee GB/T 3287 B1-1×1/2×3/4-Fe-D.
Example 5: Reducing tee with main pipe fitting sizes 1 and 3/4 and branch pipe fitting size 1/2, black finish, design symbol B, designated as Tee GB/T 3287 B1-1×3/4×1/2-Fe-B-b.
Example 6: Equal female tee with pipe fitting size 3/4, hot-dip zinc-coated, design symbol D, designated as Tee GB/T 3287 B1-3/4-Zn-D.
Contents Foreword 1 Scope 2 Normative references 3 Terms and definitions 4 Product classification 5 Requirements 6 Test methods 7 Inspection rules 8 Marking, packaging, transportation and storage Annex A (Normative) Types and dimensions of Type I pipe fittings Annex B (Normative) Types and dimensions of Type II pipe fittings Annex C (Normative) Types and dimensions of Type III pipe fittings Annex D (Normative) Malleability (flattening rate) test Annex E (Informative) Inert packing Bibliography
