How to Check Whether The Welding Flange Material Meets The Requirements?

What is Welding Flange

The welded flange is the part where the pipe is connected to each other and is connected to the pipe end. There are holes on the welded flange, and the bolts make the two flanges tightly connected. Sealed with intermittent gaskets. A welded flange is a disc-shaped part that is most commonly found in plumbing.

Application of welded flanges

Welded flanges are widely used in petrochemical, municipal, food and medicine, energy and power and other fields, and are used for sealing connections of pipeline systems. In the petrochemical industry, 316L stainless steel butt welding flanges are suitable for high-pressure, corrosive media (e.g., hydrochloric acid, hydrogen sulfide); Carbon steel flat welded flanges are commonly used in the construction industry to connect fire protection and heating pipelines; In the food and pharmaceutical field, 304/316L stainless steel sanitary flanges are used to ensure cleanliness and sterility; In the energy industry, alloy steel butt welding flanges can withstand high temperature and high pressure steam, while duplex steel flanges are used in anti-corrosion scenarios in nuclear power and offshore engineering. The selection of its type (such as butt welding, flat welding) and material adaptability (carbon steel, stainless steel, alloy) need to be comprehensively determined according to the requirements of working conditions (pressure, temperature, medium characteristics) to ensure the safety and economy of the system.

What are The Consequences of The Welding Flange Material Not Meeting The Requirements

Non-compliance with the requirements of the welded flange material may lead to the following serious consequences:

1. Safety hazards

Structural failure: If a material with insufficient strength (such as replacing alloy steel with cast iron) may cause plastic deformation or brittle fracture in a high-pressure and high-temperature environment, resulting in pipe bursting or even explosion.

Corrosion perforation: The selection of non-corrosion-resistant materials (such as carbon steel for chloride-containing media) will accelerate the corrosion of the flange body or weld, form a leakage channel, and cause media leakage or fire.

2. Failure of functionality

Seal failure: The hardness of the material is not up to standard (such as the high hardness of stainless steel) may lead to the deformation of the flange sealing surface, and the gasket cannot be effectively fitted, resulting in medium leakage.

High temperature creep: When ordinary carbon steel is used to replace heat-resistant alloy steel under high temperature conditions, the flange will gradually relax due to creep and eventually lose the connection strength.

3. Economic loss

Maintenance costs: Leaks or failures caused by material problems need to be stopped for maintenance, and the cost of replacing flanges and related equipment can be as high as hundreds of thousands of yuan, especially in continuous production industries such as petrochemical industry.

Collateral losses: Leakage of media can contaminate the environment or damage downstream equipment (e.g., precision instruments), and indirect losses are difficult to estimate.

4. Compliance Risks

Legal liability: If a safety accident is caused by material problems, the enterprise may face administrative penalties, civil compensation and even criminal liability (such as the crime of major liability accident under the Work Safety Law).

Qualification revocation: The use of non-standard materials in violation of industry standards (such as GB/T 9115) may lead to unqualified project acceptance and blacklisting of enterprise qualifications.

How to Check Whether The Welding Flange Material Meets The Requirements

To test whether the welded flange material meets the requirements, it is necessary to combine chemical composition analysis, physical property testing and non-destructive testing, and the specific steps are as follows:

1. Chemical composition testing

Spectroscopy

A portable spectrometer (e.g., XRF) is used to quickly scan the flange surface to detect key elements such as C, Cr, Ni, Mo, etc., and compare them with standard values such as 304 stainless steel, which require Cr≥18% and Ni≥8%.

It is suitable for on-site rapid screening with an accuracy of ±0.1%.

Laboratory chemical analysis

After sampling, the composition is accurately determined by titration, inductively coupled plasma (ICP) and other methods, and the results are more authoritative, which can be used in dispute arbitration or high-demand scenarios.

2. Physical performance test

Hardness test

Use a Rockwell (HRB) or Brinell (HB) hardness tester to test the hardness of materials, such as carbon steel Q235 hardness is about HB120-160, stainless steel 304 is about HB≤187.

Tensile test

The mechanical properties such as yield strength and tensile strength are tested by the testing machine, such as the yield strength of 20# steel ≥245MPa, and the yield strength of 316L stainless steel ≥205MPa.

3. Non-Destructive Testing (NDT)

Ultrasonic Flaw Detection (UT)

Detection of internal defects (porosity, cracks) and, in particular, evaluation of post-weld quality, in accordance with standards such as JB/T 4730.

Magnetic Particle Testing (MT)

It is used for surface or near-surface defect detection of ferromagnetic materials (carbon steel, alloy steel) with high sensitivity.

4. Appearance and size inspection

Visual inspection

Observe whether there are defects such as rust, slag inclusion, and lack of weld penetration on the surface, and the flange sealing surface should be smooth and free of scratches.

Dimensional measurements

Use vernier calipers and micrometers to check flange thickness, bolt hole spacing, and other dimensions to ensure compliance with ASME B16.5 or GB/T 9115 standards.

5. Identification and document verification

Certificate of Material (COC)

Check the COC report provided by the supplier to confirm that the data such as heat number, chemical composition, and mechanical properties are consistent with the procurement requirements.

Standards Compliance

Check the markings on the flange (e.g., material code, pressure rating), e.g. WN 300# for butt weld flange 300 lb. class.

Precautions

Sample representativeness: Avoid sampling in the weld or heat-affected zone to ensure that the test results reflect the true composition of the base metal.

Third-party verification: For critical items (e.g., high-pressure pipe flanges), it is recommended to entrust a qualified laboratory to conduct full testing.

Environmental impact: High temperature and corrosive media may cause material performance degradation, and regular re-inspection is required.

Through the comprehensive verification of the above methods, it can ensure that the welded flange material meets the design specifications and the requirements of the use environment.

Supplier of Flanges

LTZC has been focusing on flange manufacturing for 20 years, providing carbon steel, stainless steel, high-pressure flanges and customized products, covering all categories of butt welding, flat welding, threading and blind plates, and strictly complying with ASME, DIN, JIS international standards. We have passed ISO 9001 and API 6A certifications from raw materials to finished products to ensure the stable performance of our products in high-pressure scenarios such as petrochemical, energy, and shipbuilding.

Own factory + intelligent warehousing, support 72-hour emergency delivery, can be matched with bolt gasket one-stop procurement. In the past 20 years, it has served 500+ enterprises around the world, saving more than 15% of costs for customers such as PetroChina and European Energy Group. If you need a flange, find LTZC - fast, economical and stable.