Forged Branch Fitting Testing

Forged branch outlet fitting inspection mainly conducts scientific testing and analysis on the chemical composition analysis, mechanical property testing, dimension and geometric shape inspection, surface quality and non-destructive testing, pressure testing and sealing verification, and metallographic structure examination, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Chemical composition analysis: The raw materials (such as the carbon steels, alloy steels and stainless steels) used for the forged branch outlet fittings are sampled, and a spectrometer or chemical analysis method is used to precisely determine the contents of the key elements such as the carbon (C), manganese (Mn), silicon (Si), sulphur (S), phosphorus (P), chromium (Cr), nickel (Ni) and molybdenum (Mo), ensuring that they meet the requirements of the material standards (such as ASTM A105 and A182). This is the basis for guaranteeing the mechanical properties and corrosion resistance of the products.

Mechanical property testing: The mechanical properties of the forged branch outlet fittings are evaluated through the tensile testing and hardness testing. The tensile testing determines its yield strength, tensile strength and elongation; the hardness testing (Brinell HB, Rockwell HRC) is carried out at multiple points on the body and the key transition areas of the branch outlet fitting, verifying whether it meets the strength and toughness required by the design specifications, preventing the brittle fracture or excessive deformation under the pressure or load.

Dimension and geometric shape inspection: High-precision callipers, micrometers and coordinate measuring machines (CMM) are used to comprehensively measure the key dimensions such as the outlet pipe outer diameter, wall thickness, branch height, main pipe opening size, bevel angle and total length of the branch outlet fitting. At the same time, the geometric tolerances such as the concentricity and perpendicularity are inspected, ensuring that the product can precisely match the piping system, avoiding the installation difficulties and stress concentration.

Surface quality and non-destructive testing: The inner and outer surfaces of the forged branch outlet fitting are visually inspected for the forging defects such as the cracks, folds, scars and laps, as well as the mechanical damages. Then the magnetic particle testing (MT) or penetrant testing (PT) is applied to check the surface and near-surface defects; the ultrasonic testing (UT) or radiographic testing (RT) is used to detect whether there are the volumetric or planar defects such as the inclusions, blowholes and lack of fusion inside, ensuring the structural integrity.

Pressure testing and sealing verification: This is the key item for verifying the pressure-bearing capacity and sealing performance of the product. The hydrostatic testing is usually carried out. The branch outlet fitting is installed on the test fixture, pressurized to the specified test pressure (usually 1.5 times the design pressure) and the pressure is maintained for a certain time, checking whether there are the leakage, water seepage or permanent deformation. For the occasions with the special requirements, the pneumatic testing may also be required.

Metallographic structure examination: The specimens of the forged branch outlet fitting are cut, and after grinding, polishing and etching, the microstructure such as the grain size, phase composition, and the grade and distribution of the non-metallic inclusions is observed under a metallographic microscope. This testing is used to evaluate the forging process quality and heat treatment effect of the material, and indirectly judge its mechanical properties and long-term service reliability.

Material marking and traceability verification: It is checked whether the steel stamp markings on the product body are clear and complete. The contents usually include the material grade, specification and model, pressure class, applicable standard, manufacturer's trademark or code. The consistency between the markings and the accompanying quality certificates (such as the material certificates and certificates of conformity) is verified, ensuring the full traceability of the product. This is an important link of the quality management system.

Testing Scope

Products of the different pressure classes: The testing covers the forged branch outlet fittings of the pressure classes Class 150, 300, 600, 900, 1500, 2500 and even higher. The different pressure classes have the significant differences in the requirements for the mechanical properties, wall thickness and test pressures of the materials, and the testing schemes and judgement standards need to be adjusted accordingly according to the specific classes, ensuring the safety under the design conditions.

Multiple connection forms: The testing scope includes the forged branch outlet fittings with the different end connection forms such as the butt welding (BW), socket welding (SW) and threaded (THD). The testing emphasis varies, for example, the butt welding branch outlet fittings focus on the bevel dimensions and non-destructive testing; the socket welding and threaded branch outlet fittings need to additionally check the thread precision, socket depth and fitting tolerances.

Full specification size series: The forged branch outlet fittings from DN15 (1/2") to DN600 (24") and even larger sizes are within the routine testing scope. For the large-diameter or reducing branch outlet fittings, their testing items (such as the wall thickness distribution and geometric dimensions) are more complex, and may require the larger testing equipment or customized tooling.

Multiple material types: The testing is applicable to the forged branch outlet fittings of the various materials such as the carbon steels (such as A105), alloy steels (such as F11 and F22), austenitic stainless steels (such as 304 and 316) and duplex stainless steels. The testing emphasis of the different materials is different. For example, the stainless steels need to emphatically control the ferrite content and carry out the intergranular corrosion testing, while the alloy steels need to pay attention to their temper embrittlement tendency.

Whole manufacturing process: The testing runs through the whole manufacturing process from the incoming re-inspection of the raw materials, forging process, after the heat treatment, to the machined finished products and the final testing. This includes the inspection of the intermediate products (such as the forged blanks) and the final inspection before the ex-factory of the finished products, realizing the process quality control rather than only the final acceptance.

New and old products and in-service equipment: The testing is not only for the newly manufactured branch outlet fittings, but also applicable to the re-inspection of the stock products, pre-installation inspection, and the periodic inspection or failure analysis of the branch outlet fittings on the in-service piping systems. The in-service testing focuses more on the wall thickness reduction measurement, surface crack detection and corrosion condition evaluation.

Testing Methods

Spectrometry analysis method and wet chemical analysis: For the chemical composition, the portable or bench-type spark direct-reading optical emission spectrometers (OES) are often used for the rapid on-site screening, which is efficient and non-destructive. For the arbitration or precise analysis, the wet chemical methods such as the inductively coupled plasma optical emission spectrometry (ICP-OES) or carbon-sulphur analysers are adopted, whose results are more accurate and are the basis for issuing the reports.

Universal material testing machine tensile method: The tensile testing in the mechanical properties is strictly carried out in accordance with the standards such as ASTM A370 or GB/T 228.1. The standard tensile specimens are processed from the prolongation sections of the product or the same heat batch samples, loaded at the specified rate on the universal testing machine until the fracture, and the data such as the yield strength, tensile strength and elongation after fracture are automatically recorded and calculated.

Coordinate measurement and optical scanning: For the detection of the complex geometric dimensions and geometric tolerances, the coordinate measuring machines (CMM) are increasingly adopted. For the external contours, the three-dimensional optical scanners can rapidly obtain the high-density point cloud data, carry out the comparison and analysis with the CAD models, intuitively display the dimensional deviations, and the efficiency is far higher than the traditional manual measurement.

Magnetic particle and penetrant surface testing methods: The magnetic particle testing (MT) is applicable to the ferromagnetic materials, and finds the surface and near-surface defects through the magnetization, application of the magnetic particles and observation of the magnetic indications. The penetrant testing (PT) is applicable to all the non-porous materials, and displays the surface open defects by applying the penetrant, cleaning and developer. Both are the routine and effective surface defect detection means.

Ultrasonic pulse-echo method and radiographic method: The ultrasonic testing (UT) utilizes the principle of the reflection of the high-frequency sound waves when they encounter the defects during the propagation in the material, and can precisely determine the position, equivalent size and depth of the internal defects. It is particularly suitable for the thick-walled products. The radiographic testing (RT) utilizes the X or γ rays to penetrate the object and image on the film, which can intuitively display the shape and distribution of the internal defects, but is more sensitive to the volumetric defects.

Hydrostatic testing method: The pressure testing usually adopts the hydrostatic testing method. All the openings of the branch outlet fitting are sealed and filled with water, after the air is exhausted, the pressure is slowly increased to the specified test pressure with a pressure testing pump, and the pressure is maintained for not less than 10 minutes usually. During this period, it is checked whether the pressure gauge is stable and whether there are the leakage, sweating or visible deformation of the body and all the connection parts.

Testing Standards

Domestic Standards:

1. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

3. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

4. GB/T 232-2010, Metallic materials — Bend test method

5. GB/T 10125-2021, Corrosion tests in artificial atmospheres — Salt spray tests

International Standards:

1. ASTM A105, Standard specification for carbon steel forgings for piping applications

2. ASTM A182, Standard specification for forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service

3. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

4. ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Direct-reading optical emission spectrometer and carbon-sulphur analyser: The direct-reading optical emission spectrometer is the core equipment for the chemical composition analysis, which can simultaneously analyse the contents of the multiple elements in the sample within tens of seconds. The carbon-sulphur analyser is specially used to precisely determine the contents of the two key elements of the carbon and sulphur in the material, and its analysis results are crucial for the material performance evaluation.

Universal material testing machine and hardness testers: The microcomputer-controlled electro-hydraulic servo universal testing machine is used to complete the mechanical property tests such as the tensile and compression, with the high precision and automatic data acquisition functions. For the hardness testing, the Brinell hardness testers, Rockwell hardness testers or portable Leeb hardness testers are equipped, used for the rapid hardness testing and conversion at the different parts.

Coordinate measuring machine and large calliper gauges: The coordinate measuring machine (CMM) is the equipment for the high-precision and complex dimension inspection. Through the probe contact with the workpiece, the three-dimensional coordinate data can be precisely obtained. For the large-diameter branch outlet fittings, the special tools such as the diameter tapes, large digital calliper gauges and ultrasonic thickness gauges also need to be used to measure the circumference, diameter and wall thickness.

Complete non-destructive testing equipment: Including the magnetic particle flaw detectors (with the yoke type or coil type), dye penetrant testing kits, ultrasonic flaw detectors (with the multiple angle probes) and radiographic flaw detection equipment (X-ray machines or γ sources). The modern ultrasonic phased array (PAUT) and digital radiography (DR) equipment can provide the more efficient and clearer detection results.

Metallographic microscope and specimen preparation system: The metallographic analysis needs a series of sample preparation equipment such as the cutting machines, mounting machines and grinding and polishing machines, to prepare the samples into the smooth mirror surfaces that can be observed. The research-grade upright or inverted metallographic microscopes, combined with the image analysis software, are used to observe, photograph and quantitatively analyse the microstructure of the material.

Pressure testing system: Composed of a pressure testing pump (manual or electric), high-pressure pipelines, precision pressure gauges or pressure sensors, dedicated sealing test tooling (flanges, blind plates and plugs) and safety protection facilities. The system needs to be able to stably provide and maintain the test pressure higher than the working pressure of the product, and ensure the safety and controllability of the testing process.

Surface roughness tester and profilometer: Used to quantitatively detect the surface roughness Ra values of the sealing surfaces (such as the bevel surfaces and threads) of the branch outlet fitting. The profilometer can also measure the micro-geometric shapes of the sealing surfaces, ensuring that they meet the flatness or specific texture requirements required for the sealing. This is particularly important for the sealing performance of the socket welding and threaded connections.