How to choose suitable industrial stainless steel pipes

Choosing suitable industrial stainless steel pipes requires comprehensive consideration of the use environment, performance requirements, cost budget and other factors. The following are specific selection points and suggestions:

I. Clarify the use scenarios and working conditions

1. Medium type

Corrosive media: such as chemical solutions, seawater, acidic/alkaline liquids, etc., focus on the corrosion resistance of stainless steel (such as 316L, 2205 duplex steel, etc.).

High temperature media: such as steam, high temperature oil, etc., high temperature resistant stainless steel (such as 310S, 321, etc.) needs to be selected.

High pressure media: such as high pressure pipeline systems, the strength and wall thickness of the pipe material (such as seamless steel pipes, thick wall pipes) need to be considered.

2. Temperature and pressure range

Temperature: Low temperature environment (such as -196℃ liquid nitrogen) needs to select materials with good low temperature toughness (such as 304L, 316L); high temperature environment (such as above 600℃) needs to select heat-resistant steel (such as 310S, Incoloy 800).

Pressure: Select the pipe wall thickness grade (such as Sch40, Sch80) according to the design pressure of the pipeline system. Seamless steel pipes are preferred for high-pressure scenarios.

3. Installation environment

Indoor/outdoor: The outdoor environment needs to consider the impact of ultraviolet rays and humidity on stainless steel (such as 304 may rust in a humid environment, so 316 or higher grades should be selected).

Vibration or impact scenarios: For equipment connecting pipes with large mechanical vibration, pipes with high strength and good vibration resistance (such as thick-walled seamless pipes) should be selected.

2. Select the appropriate stainless steel material

1. Common industrial stainless steel types and characteristics

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2. Material selection logic

Corrosion priority: If the medium is highly corrosive, duplex steel (such as 2205) or high-nickel stainless steel (such as 904L) is preferred.

Strength priority: Duplex steel or thick-walled austenitic stainless steel is selected for high-pressure or load-bearing scenarios.

Cost control: 304 can be selected for non-corrosive scenarios, and 316L can be selected for moderate corrosion to avoid excessive selection and increase costs.

3. Determine pipe specifications and manufacturing standards

1. Specifications

Outer diameter and wall thickness: Calculate the pipe diameter according to the flow rate (refer to the fluid mechanics formula), and the wall thickness must meet the pressure level (such as ASME B36.10 seamless steel pipe standard).

Length and tolerance: Industrial pipes are usually fixed in length (such as 6 meters, 12 meters), and the tolerance range must be confirmed (such as outer diameter ±1%, wall thickness ±0.1mm).

2. Manufacturing process

Seamless steel pipe: Made by perforation hot rolling, it has high strength and uniform performance, and is suitable for high pressure, high temperature, and high demand scenarios (such as petrochemicals, electricity).

Welded steel pipe: Made of steel strip coils, it has low cost and high production efficiency, and is suitable for low pressure, non-corrosive or general corrosion scenarios (such as construction, water pipes).

3. Implementation standards

Domestic standards: GB/T 14976 (stainless steel seamless steel pipes for fluid transportation), GB/T 12771 (stainless steel welded steel pipes for fluid transportation).

International standards: ASTM A312 (American standard austenitic stainless steel seamless/welded steel pipe), EN 10216-5 (European standard pressure-bearing stainless steel pipe).

IV. Pay attention to pipe performance and quality verification

1. Key performance test

Corrosion resistance test: such as intergranular corrosion test (GB/T 4334), salt spray test (ISO 9227), to ensure that the material does not rust in the target environment.

Mechanical property test: tensile test (measure yield strength, tensile strength), impact test (measure low temperature toughness), to meet the strength requirements of working conditions.

Pressure test: hydraulic test (such as GB/T 241) or air pressure test to ensure that the pipeline is leak-free.

2. Quality certification documents

Suppliers are required to provide material certificates (including chemical composition, mechanical properties), non-destructive testing reports (such as ultrasonic testing UT, eddy current testing ET), and heat treatment reports (if solution treatment is required).

5. Consider cost and supply chain factors

1. Cost structure

Material cost: Duplex steel>316L>304, seamless pipe>welded pipe.

Processing cost: Thick-walled pipes and special specification pipes are difficult to process and have higher costs.

Maintenance cost: High corrosion-resistant materials have high initial costs, but long-term maintenance costs are low (such as reducing replacement frequency).

2. Supplier selection

Give priority to large steel mills or first-level agents to ensure that the source of pipes is regular (such as Baosteel, Taigang, and Qingshan Holdings).

A third-party inspection report is required to avoid using "non-standard" or inferior recycled materials to produce pipes.

6. Other precautions

1. Processing and connection methods

Welding: Austenitic stainless steel requires matching welding wire (such as ER308L for 304 and ER316L for 316), and duplex steel requires controlled welding heat input to prevent embrittlement.

Flange connection: Butt welding flanges are used for high-pressure scenarios, and flat welding flanges are used for low-pressure scenarios. It is necessary to pay attention to the matching of flange material and pipe material.

2. Surface treatment

Pickling and passivation: remove welding oxide scale and improve corrosion resistance (applicable to food and pharmaceutical industries).

Polishing: inner wall polishing can reduce fluid resistance and is suitable for high-purity media (such as pharmaceutical and electronic grade pure water).

Summary: Selection flow chart

Through the above steps, stainless steel pipes that meet industrial needs can be systematically selected. If the working conditions are complex (such as mixed corrosion + high pressure + high temperature), it is recommended to consult a professional pipe supplier or design institute for joint selection.

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Tags: stainless steel pipes, Material selection logic, Specifications