Food-grade stainless steel pipe, Sanitary stainless steel pipe

What is food-grade stainless steel pipe?

Food-grade stainless steel pipe, also known as sanitary stainless steel pipe, is a pipe material specially used in industries with strict sanitation requirements such as food, beverage, and pharmaceuticals. It must meet the core requirements of food safety, corrosion resistance, and easy cleaning. Food-grade stainless steel pipes can be divided into seamless stainless steel pipes and welded stainless steel pipes according to the manufacturing process. Common materials are 304 and 316.

Features of food-grade stainless steel pipes:

Food-grade stainless steel pipes are environmentally friendly materials that can directly contact food and do not precipitate harmful substances, meeting food safety requirements. Its main features include:

1. Corrosion resistance: Since a large amount of acid and alkali may be exposed during food production, stainless steel pipes are required to have excellent corrosion resistance.
2. Low lead content: The heavy metal lead content in food-grade stainless steel is much lower than that of general stainless steel to ensure food safety.

3. High cleanliness: The inner and outer surfaces of food-grade stainless steel pipes are usually polished to achieve a higher cleanliness standard to prevent the fluid in the pipe from forming wall hanging and contamination, and prevent bacterial residues.

Common materials for food-grade stainless steel pipes:

Common materials for food-grade stainless steel pipes include austenitic stainless steel materials such as 304 stainless steel and 316 stainless steel. These materials have excellent corrosion resistance, high strength and good processing performance, and can meet the requirements of food-grade stainless steel pipes.

304 (06Cr19Ni10): General type, resistant to weak acids and weak alkalis. Commonly used in dairy and beverage pipelines.
316L (022Cr17Ni12Mo2): Contains molybdenum, resistant to chloride ion corrosion. Commonly used in seawater processing and high-salt foods.

International certification standards:

US: FDA 21 CFR 175.300 (Food Contact Material Standard)
EU: EC 1935/2004 (Food Grade Material Regulations)
China: GB 4806.9-2016 (National Food Safety Standard)

Surface treatment of food-grade stainless steel pipes:

To ensure hygienic performance, special processes are required to treat the inner wall:

a. Mechanical polishing (BA/MP)
Surface roughness Ra≤0.8μm, reduce attachments.

b. Electrolytic polishing (EP)
Higher microscopic flatness (Ra≤0.4μm), used in pharmaceuticals and high-end beverages.

c. Pickling passivation (AP)

Remove the oxide layer and form a passivation film to improve corrosion resistance.

Core applications of food-grade stainless steel pipes:

Food-grade stainless steel pipes are mainly used in production equipment and assembly lines such as food, beverages, alcohol, and bioengineering. These fields have extremely high requirements for the cleanliness, corrosion resistance and safety of pipes, so food-grade stainless steel pipes have become the preferred material in these fields.

1. Liquid food transportation
Thin-walled stainless steel pipes with internal and external polishing are often used in drinking water pipes and dairy equipment pipes, such as milk, juice, beer and other pipe systems (commonly used 316L). They can also transport cold water and hot water to ensure the safety and purity of drinking water and avoid secondary contamination of water.

2. Food processing machinery

Since stainless steel has good corrosion resistance, it can be used in the production of various food machinery and packaging equipment, such as beverage filling machines, fermentation tanks, and sterilization equipment connecting pipes. In addition, it can also be used in cold storage, refrigerated trucks and other fields.

3. Pharmaceutical equipment
Due to the high requirements of clean rooms for materials, stainless steel is one of the commonly used materials for manufacturing drugs. For example, it is widely used in pharmaceutical factory pipeline systems, syringes, and liquid medicine storage containers. Such as water for injection (WFI) pipelines, bioreactors (EP grade required).

4. Catering industry
In the catering industry, food-grade stainless steel pipes are used to make tableware and storage containers. Its antioxidant and wear resistance enable tableware to resist corrosion from acids, alkalis and other substances in food, and will not release harmful substances, ensuring the durability and safety of tableware. Such as central kitchen water pipes and commercial dishwasher pipelines.

Should food-grade stainless steel choose seamless pipes or welded pipes?

1. Comparative analysis of hygienic performance
Since seamless stainless steel pipes do not require welding, their inner and outer surfaces are smoother and not easy to accumulate dirt, which is conducive to keeping the inside of the pipe clean and hygienic, and reducing the risk of bacterial growth. In contrast, stainless steel welded pipes may have dead corners that are difficult to clean at the welding point, which increases the difficulty of cleaning and the possibility of bacterial growth.

2. Durability assessment
Seamless stainless steel pipes are treated with high temperature and high pressure during the production process, and have good strength and toughness, and can withstand greater pressure. Although welded pipes can also meet certain usage requirements, cracking and leakage may occur at the welds under long-term high pressure and high temperature environments, affecting the service life.

3. Cost-effectiveness considerations
Welded pipes have price advantages due to their relatively simple production process and low cost. However, in the long run, seamless stainless steel pipes can reduce maintenance costs and extend service life with their excellent hygiene and durability, thereby achieving better cost-effectiveness.

4. Selection in special application scenarios
In some scenarios with extremely strict cost requirements or special requirements for installation speed, stainless steel welded pipes have certain advantages due to their low cost and convenient installation. However, in most cases, considering the hygiene and safety standards of the food and dairy industry, seamless stainless steel pipes are more suitable.

How to identify genuine and fake food-grade stainless steel pipes?

1. Look at the material report
Ask for an SGS test report to confirm that the chromium (Cr) and nickel (Ni) content meet the standards.

2. Check the surface quality
The inner wall should be free of scratches and burrs, and can be inspected by endoscope.

3. Look for certification marks
Such as FDA, GB 4806.9, ISO 2037 and other certifications.

4. Acid reagent test
304/316 should not change color or corrode in citric acid or acetic acid.

Standards and requirements:

The standards and requirements for food-grade stainless steel pipes mainly include the following aspects:

Raw material requirements:
The main body should be made of austenitic stainless steel, austenitic ferritic stainless steel, ferritic stainless steel and other stainless steel materials.
Martensitic stainless steel materials can also be used, but the content of harmful elements such as lead must be strictly controlled.

Appearance requirements:
The inner and outer surfaces of the pipe should be smooth, free of cracks, rust, oil stains and other defects.
The weld should be flat and smooth, without undercuts, pores and other defects.

Physical and chemical indicators:
Meet the requirements for trace element migration in the standard "Metallic Materials and Products for Food Contact".
The mechanical properties of the pipe, such as tensile strength, yield strength, and elongation, shall comply with the relevant standards.

Surface roughness:
The surface roughness Ra value of the surface in contact with food shall not be greater than 0.8μm, the Ra value of other surfaces shall not be greater than 2.5μm, and the Rz value of the weld surface shall not be greater than 12.5μm.

Other requirements:
The manufacturing process of the pipe shall comply with the relevant standards, such as welding, polishing and other processes shall meet the specified quality requirements.

The pipe shall undergo strict inspection and testing to ensure that it meets food grade requirements.

Read more: Food grade stainless steel 304 vs 316: Which one is safer? or Material requirements for food grade seamless stainless steel pipes