GB/T 34635-2017Flange connections (English PDF)

1 Scope

This Standard specifies the types and parameters, dimensions and tolerances, materials, type selection, surface treatment, marking, labeling, as well as performance and test requirements of flange connections.

This Standard applies to flange connections for hydraulic fluid transmission and general purposes with maximum working pressure of 3.5 MPa ~ 42 MPa and nominal diameter of DN10 ~ DN127.

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 70.1, Hexagon socket head cap screws

GB/T 97.1, Plain washers - Product grade A

GB/T 131, Geometrical Product Specifications (GPS) - Indication of surface texture in technical product documentation

GB/T 1804-2000, General tolerances - Tolerances for linear and angular dimensions without individual tolerance indications

GB/T 3098.1, Mechanical properties of fasteners - Bolts, screws and studs

GB/T 3098.2, Mechanical properties of fasteners - Nuts - Coarse thread

GB/T 3141, Industrial liquid lubricants - ISO viscosity classification

GB/T 3452.2-2007, Fluid power systems - O-rings - Part 2: Quality acceptance criteria

GB/T 5783, Hexagon Head Bolts - Full Thread

GB/T 6170, Hexagon Nuts, Style 1

GB/T 7631.2, Lubricants, industrial oils and related products (class L) - Classification - Part 2: Family H (Hydraulic systems)

GB/T 10125, Corrosion tests in artificial atmospheres - Salt spray tests

4 Dimensions and tolerances

5 Materials

6 Type selection

6.1 For flange connections that comply with this Standard, attention shall be paid to the difference in maximum working pressure and size between the light and heavy series.

Flange connections of the light and heavy series are not interchangeable.

6.2 For split or integral flange connections, according to the inner diameter of the flange joint or the corresponding flange nominal diameter (DN) of the maximum pore diameter of the flange block, select the size of the flange connection. When the maximum working pressure is 2 MPa, it is recommended to use the flange pressure plate with two diagonal bolt holes specified in Appendix C.

6.3 For split or integral flange connections, the nominal sizes (DN) of the flange pressure plate, oil port end and flange joint must be consistent.

6.4 If the flange needs to be installed on the flange block, it is necessary to measure the distance between the bolt holes and the size of the bolt holes to select the appropriate flange joint and flange pressure plate. To prevent confusion between light and heavy series flanges, the distance measurement needs to be accurate to 1 mm or even higher.

6.5 If it is to be installed with a flange joint, the diameter and thickness must be measured accurately to 0.5 mm or even higher.

6.6 Select the corresponding flange pressure plate type: integral flange pressure plate, split flange pressure plate or square flange pressure plate.

6.7 When designing the system, it is necessary to consider that when the peak pressure in the system is higher than the maximum pressure, the performance of the flange connection may be reduced.

7 Surface treatment

7.1 Unless otherwise specified by the supplier or purchaser, the outer surface of all carbon steel flange joints (except welded flange joints) and flange pressure plates shall be surface treated and shall pass the 72 h salt spray test required by GB/T 10125, unless otherwise specified by the supplier or purchaser; welded flange joints shall be subjected to oil immersion or phosphating, or other surface treatment methods that will not damage their welding performance, and shall pass the 16 h neutral salt spray test specified in GB/T 10125.

7.2 Bolts and washers need to be oiled or phosphated, or treated in other ways that will not cause hydrogen embrittlement, and meet or even exceed the 16 h salt spray test required by GB/T 10125.

7.3 Except for the following cases, any red rust on any part during the above salt spray test shall be judged as unqualified:

a) all internal holes;

b) places where mechanical deformation may occur, such as the hexagonal side of the nut, the teeth and tooth tips of the thread, or test samples affected by mass production or transportation;

c) coating surface affected after other mechanical deformation treatments such as crimping, expansion, pipe bending, etc.;

d) parts from which the components are suspended or which are exposed to sticking and condensation accumulation in the test chamber.

7.4 The surface treatment of components conforming to this Standard shall not use zinc plating containing chromium.

7.5 During storage and transportation, the internal fluid channels shall be treated with anti-corrosion measures.

7.6 All connecting parts shall be deburred, descaled and free of waste, as these factors will affect the service life of the product. Unless otherwise specified, the roughness of all machined surfaces is Ra <= 6.3 µm.

7.7 The roughness of the sealing surface shall be guaranteed, and the surface roughness of the annular knife mark shall be Ra <=3.2 µm. There shall be no vertical, radial or spiral scratches with a width greater than 0.13 mm inside the O-groove and on the bottom of the groove.

8 Marking

Flange joints shall be permanently marked with at least the manufacturer's name or trademark.

9 Labeling

10 Performance and test requirements