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    Stainless steel Coiled Capillary Tubing

    1. Scope

    This standard specifies the definition, naming, requirements, test methods, inspection rules, marking, packaging and product quality certificate of stainless steel coiled capillary pipe.

    This standard is suitable for the production of austenitic stainless steel as raw material by welding, for automotive, refrigeration, ship building, instrumentation, marine exploration in the stainless steel coiled capillary tube, other variants of products can also refer to the use.


    1. Specification references

    The following documents are indispensable for the application of this document. For dated references, only the dated edition applies to this document, and the most recent version of the referenced document (including all amendments) applies to documents that are not dated.


    GB/T 222                                Chemical composition allows deviation

    GB/T 223 Series                    Methods for chemical analysis of steel and alloys

    GB/T 228.1                            Metallic materials - Tensile testing - Part 1: Room temperature test method

    GB/T 230.1                            Metallic materials - Rockwell hardness test

    GB/T 241                               Hydraulic test method for stainless Capillary pipe

    GB/T 246                               flattening test method for stainless Capillary pipe

    GB/T 2102                             Acceptance, packing, marking and quality certificate of stainless coiled Capillary tubing

    GB/T 3090                             Stainless steel small diameter seamless pipe

    GB/T 11170                           Determination of multi-element content of stainless steel coiled tubing


    1. Terms and definitions

    The following terms and definitions apply to this standard

         3.1 Control

    Stainless steel coiled capillary tubing is mainly used in hydraulic control system, it must go through the hydraulic test, the coiled pipe to 7.0MPa for the test pressure.

         3.2 Name


    SAKY—8X1X300 (304)

    OD 8mm Thickness 1mm Length 300m Material 304(*)Sakysteel coiled capillary tubing. Remark *: Material base on 4.2 request test;


    4 Request

    4.1 Stainless steel coiled capillary tube shall be manufactured in accordance with the technical documents approved by the prescribed procedures and shall comply with the requirements of this standard.

    4.2 For the manufacture of stainless capillary tubing line of the material, the chemical composition should be consistent with Table 1, the mechanical properties should be consistent with the provisions of Table 2. If the customer has the special requirements, according to customer requirements, the chemical composition of the product, mechanical properties should meet the requirements of the corresponding standards.


    Table 1  Coiled Capillary Chemical Composition


    Chemical Composition

    C  ≤

    Mn ≤

    P ≤

    S ≤

    Si ≤























    Table 2  Coiled Capillary mechanical properties


    Tensile Strength

    Elongation after breaking

    Hardness test

    RM(MPa) ≥

    A% ≥











    4.3  Surface treatment state and surface quality:

     Stainless steel coiled capillary tubing should be bright treatment, inside and outside the surface should be smooth, no stratification, cracks, folding, miscellaneous skin, twisted, etc., allowed to have no more than a slight tolerance of wall thickness of the slight scratch, pressure pit, Depression, protrusion and so on.

    4.4 Geometric dimensions

    4.4.1 Stainless steel coiled capillary tubing length,outside Diameter, wall thickness and other requirements should be consistent with the provisions of Table 3.

    4.4.2 Table 3 shows the OD of the deviation is not sufficient to indicate the thin-walled tube oval. The deviation between the maximum and minimum diameters of the cross sections of these control pipes shall not exceed 200% of the allowable deviation of the outer diameters listed in Table 3, and the average diameter of any section shall be within the permissible deviation.

    Table 3  Geometric dimensions & Allow deviation



    DO Allow deviation(mm)

    Thickness Allow deviation(mm)


    Φ 3




    Φ 3.175




    Φ 6




    Φ 6.35




    Φ 8




    Φ 10




    Φ 12





    4.5 Flattening performance

          Stainless steel coiled capillary tubing flattening test, the welding should be in the direction of force 90 °, pressure to the pipe OD of 2/3, No cracks or cracks may occur after crushing.

    4.6 Hydraulic performance

          Stainless steel coiled capillary tubing by the pressure of 7.0MPa, and pressure 5mins pressure test, should be no leakage。

    4.7 Intergranular corrosion

       Stainless steel coiled capillary tubing immersed in sulfuric acid pool for 16h, 180 ° bending, no intergranular corrosion cracking.

    4.8 Raw Material Request

    4.8.1 The raw materials of the products shall conform to the relevant standards

    4.8.2 Raw materials should be selected with product standards and factory inspection of qualified products, each batch of raw materials should be tested before use before use

    5. Test Methods

    5.1 Hardness

    5.1.1 Each batch of stainless steel capillary pipe must be sampled and tested according to GB / T 230.1 for hardness testing。

    5.1.2 Each batch of sampled stainless steel coiled tubing in the test, sampling tube head, tail each time, each test must be in the same sample on the 4 point test.

    5.1.3 Test parameters

             Hardness Value:The hardness of the stainless steel coiled capillary is the average of the hardness obtained by the 4-point test, and the value should be less than the value of Table 2.

     5.2 Flattening test

          For each batch of stainless steel coiled capillaries tubing must be sampled for reverse flattening test, sampling tube head, tail each time, welding should be in the direction of 90 ° force, pressure to the pipe OD of 2/3, No cracks or cracks may occur after crushing.

    5.3 Hydraulic test

          Each stainless steel coiled capillary should be hydrostatic test, test pressure 7.0MPa, 5Mins no leakage after passing.

    5.4 Intergranular corrosion

          Each batch of sampling stainless steel coiled capillary tubing immersed in concentrated sulfuric acid 16h, 180 ° bending, no intercrystalline cracks for qualified.

    6 Test regulations

    6.1 Group approved

          To the same brand, the same furnace number, the same specifications for a number of products.


    6.2 Sampling

          The number and method of sampling of the product shall be carried out according to GB / T 3090.


    6.3 Factory inspection


    6.3.1 Stainless steel coiled capillary tubing must be factory inspection, only the project by item inspection qualified, and issued a certificate before the factory.

    6.3.2 The factory inspection items are the hardness of 4.3-44 and Table 2 of this standard.

    6.4 Type test

    6.4.1 A type test shall be carried out in any of the following cases:

             a) Normal continuous production once every two years;

             b) Change the process, structure, materials and product performance may  have an impact;

             c) No produce for more than 6 months;

             d) Quality supervision departments at all levels and users of the type of inspection requirements.