How to Choose Stainless Steel Tees Suitable for the Food and Pharmaceutical Industries

Guide to Selecting Stainless Steel Tees for the Food and Pharmaceutical Industries

The food and pharmaceutical industries have strict requirements for the hygiene, corrosion resistance, ease of cleaning, and sealing of pipes and fittings. Selection should be based on three core dimensions: medium characteristics, process standards, and compliance requirements. It should also be determined comprehensively by considering key parameters such as material, structure, connection method, and surface treatment. The specific steps and key points are as follows: 

I. Prioritize the Core Basis for Selection

Medium Characteristics: This is the primary prerequisite for selection. It is necessary to clarify the composition, pH value, temperature, pressure, and cleaning requirements of the conveyed materials:

If it is ordinary food (such as drinking water, beverages, dairy products) or neutral pharmaceutical liquid without strong corrosive components, basic sanitary-grade materials can be chosen;

If it is high-salt (such as soy sauce, pickling liquid), high-acid (such as vinegar, fruit juice, acidic raw materials for medicine), or materials containing chloride ions, alloys resistant to pitting and intergranular corrosion should be selected;

If it is culture medium for biopharmaceuticals, vaccine stock solution, or water for injection, it must meet the requirements of being sterile, pyrogen-free, and non-absorbent, and the pipe fittings should be designed without dead corners.

Industry Compliance Standards: It must comply with the mandatory certification standards in the food and pharmaceutical fields to avoid production qualification issues due to insufficient compliance:

Food Industry: Comply with GB 4806.9-2016 (Metal Materials and Products for Food Contact), 3A Sanitary Standards, FDA 21 CFR 177.2420;

Pharmaceutical Industry: Comply with GMP (Good Manufacturing Practice), USP <88> (Biocompatibility of Medical Devices), and relevant requirements of EP (European Pharmacopoeia);

Biopharmaceuticals / Injectables: Must meet the requirements for SIP (in-place sterilization) tolerance (typically 121°C, 30-minute steam sterilization).

Process and Working Conditions Parameters: Clarify the nominal diameter (DN), nominal pressure (PN), and working temperature of the pipeline, and match the pressure and temperature resistance performance of the three-way fittings:

Working Pressure: Food production lines are mostly low pressure (PN ≤ 10 bar), while pharmaceutical reactors and sterilization systems may be medium pressure (PN 10 - PN 25 bar);

Working Temperature: Conventional transportation is at room temperature, sterilization processes need to withstand high temperatures of 121 - 134°C, and some freezing processes need to withstand low temperatures below -20°C. 

II. Key Points for Core Parameter Selection

1. Material Selection: Prioritize 304/316L, upgrade to duplex steel for special conditions

Material directly determines corrosion resistance and hygiene, which is the core key in selection:

304 stainless steel contains 18% Cr and 8% Ni, is resistant to neutral medium corrosion, has a moderate cost, and is suitable for ordinary food production lines, such as drinking water, beverage, and baking ingredient transportation, as well as neutral pharmaceutical liquid and excipient transportation. Note that 304 is not resistant to high salt and high acid environments and is prone to pitting corrosion in materials with Cl⁻ content > 50mg/L.

316L stainless steel contains 2-3% Mo element, with an ultra-low carbon design (carbon content ≤ 0.03%), significantly enhanced resistance to chloride ion corrosion and intergranular corrosion, and is the mainstream choice in the food and pharmaceutical industries:

Food sector: suitable for high salt (soy sauce, pickling liquid), high acid (vinegar, fruit juice), and dairy products (containing lactic acid) transportation;

Pharmaceutical sector: suitable for acidic raw materials, organic solvents, injection water, and vaccine stock solution transportation, can withstand SIP high-temperature sterilization, and has no risk of heavy metal leaching.

Duplex steel 2205 (for special conditions) has an austenitic + ferritic duplex structure, high strength, and stronger corrosion resistance, suitable for extreme corrosive environments, such as high-concentration acid and alkali pharmaceutical liquids, seawater desalination pharmaceutical excipients, and chlorine-containing disinfectant water transportation. It is more expensive and should only be selected when 316L cannot meet the requirements.

2. Structural Selection: Dead corner-free design, prioritize Y-type three-way

Structure determines cleaning difficulty and material residue risk, and must eliminate "sanitary dead corners":

By flow channel structure: prioritize Y-type three-way, avoid T-type three-way

Y-type three-way: the branch angle is usually 60°, the flow channel is smooth, the fluid resistance is small, there are no turbulent dead corners, and materials are less likely to remain, suitable for high hygiene requirement scenarios, such as dairy fermentation liquid, vaccine stock solution, and injection water transportation, especially suitable for viscous materials (such as syrup, ointment) transportation.

T-type three-way: the branch angle is 90°, the flow channel has a right-angle dead corner, is prone to material residue and bacterial growth, and is only suitable for low hygiene requirement scenarios, such as cleaning water and cooling water branches in food factories, and wastewater discharge pipelines in pharmaceutical factories.

By manufacturing process: prioritize hydraulic bulging / forging, avoid casting

Hydraulic bulging / hot pressing: one-time forming, the inner wall of the flow channel is smooth without weld seams, no residual dead corners, meets sanitary grade requirements, and is the preferred process in the food and pharmaceutical industries;

Forging: higher strength, suitable for medium and high-pressure conditions, such as pharmaceutical reactor feed pipelines and sterilization systems;

Casting three-way: rough inner wall, prone to dirt accumulation, strictly prohibited for material transportation pipelines in food and pharmaceutical industries, only suitable for non-contact material auxiliary pipelines (such as cooling water, exhaust gas discharge).

3. Connection Method Selection: Quick-install / socket welding as the main, balancing easy disassembly and cleaning with sealing performance

Connection methods must match cleaning and maintenance requirements to ensure easy disassembly and reliable sealing:

Quick-install clamp connection (most mainstream) uses a clamp + sealing ring connection method, no welding required, fast disassembly speed, can complete pipeline disassembly and assembly within 10 minutes, convenient for CIP (online cleaning) and manual cleaning, suitable for core production pipelines in food and pharmaceutical industries, such as beverage filling lines, dairy fermentation liquid transportation, and vaccine stock solution branches. The sealing ring should be made of food-grade materials (such as silicone rubber, fluorine rubber) to withstand high-temperature sterilization and acid-base corrosion.

Socket welding connection has high welding strength and good sealing performance, no leakage risk, suitable for medium and high-pressure, high cleanliness scenarios, such as pharmaceutical reactor feed pipelines, injection water systems, and SIP sterilization pipelines. After welding, the weld seam should be polished to ensure a smooth inner wall without dead corners and avoid material residue. Threaded connections (use with caution): Threaded interfaces have crevices and dead corners, which can breed bacteria. They are only suitable for auxiliary pipelines that do not come into contact with materials, such as cleaning water and cooling water branches. They must not be used for the direct transportation of food materials or pharmaceutical liquids.

4. Surface treatment selection: Polishing is a hard requirement, and the lower the roughness, the better.

The inner surface roughness directly affects the difficulty of cleaning and the risk of microbial growth, and is a core indicator for sanitary three-way fittings:

Inner surface treatment: Electrochemical polishing must be carried out (superior to mechanical polishing), and the surface roughness must meet the following requirements:

Food industry: Ra ≤ 0.8 μm; in high-demand scenarios (such as dairy products and brewing), Ra ≤ 0.4 μm is required.

Pharmaceutical industry: For injectables and biopharmaceuticals, Ra ≤ 0.28 μm is required to ensure no material adsorption and no bacterial residue, and it can pass CIP cleaning validation.

Outer surface treatment: Acid washing and passivation or sandblasting can be used to prevent rusting on the outer surface without affecting hygiene. 

III. Selection Pitfalls and Acceptance Key Points

It is strictly prohibited to use ordinary industrial-grade three-way fittings: Industrial-grade three-way fittings have rough surfaces, weld dead corners, and the material may not meet food contact standards, which can easily lead to product contamination.

Verify the manufacturer's qualifications: Require the supplier to provide material test reports (spectral analysis), 3A/FDA/GMP certification certificates to ensure that the material and compliance standards are met.

Key acceptance indicators: After arrival, check the inner wall polishing quality (no scratches, no depressions), dimensional accuracy (nominal diameter, wall thickness), and if necessary, conduct a hydrostatic test (1.5 times the nominal pressure) to ensure no leakage.