ASTM A270 Sanitary Stainless Steel Tubing and Pipe

Steel Friend (previously known as octalsteel) brings you the ultimate guide to ASTM A270 sanitary stainless steel tubing, the go-to standard for industries like dairy, food, and bioprocessing. In this comprehensive overview, we delve into the specifications, size ranges, manufacturing processes, and more, providing you with a thorough understanding of this critical component in sanitary applications.

ASTM A270 Stainless Steel Tubing and Pipe

Specifications and Size Range

ASTM A270 defines the standards for welded seamless and heavily cold-worked welded austenitic and ferritic stainless steel sanitary tubing. This encompasses various types of stainless steel tubes, both seamless and welded, including ERW and EFW varieties. Typically, ASTM A270 sanitary tubing caters to smaller pipe diameters, ranging from 1/2” to 2 1/2”, with thicknesses varying from 0.049 inches (1.24mm) to 0.15 inches (3.81mm). The maximum outer diameter allowed for ASTM A270 tubing is 12 inches (304.8 mm). It's worth noting that inch-pound serves as the standard unit of measurement, and wall thickness tolerance should not deviate more than 12.5%.

Referred Standards

For ASTM A270 sanitary tubing, adherence to several standards is crucial to ensure quality and compliance. These include ASTM A262 for detecting intergranular corrosion, ASTM A480/A480M for general specifications regarding flat stainless steel, ASTM A923 for detecting detrimental intermetallic phase, ASTM A967 for passivation treatment, ASTM A1016/1016M for general specifications regarding alloy and stainless steel, E527 for test methods for numbering metal and alloy, ASTM B46.1 for surface structure, and ASME boiler and pressure vessel standards, among others.

Manufacturing Processes

During the manufacturing of ASTM A270 sanitary stainless steel tubing, specific points must be noted to maintain quality and integrity:

  1. Seamless steel pipes should be devoid of any welding.
  2. Welded steel pipes are produced through automatic welding processes but must not utilize metal fillers.
  3. Heavily cold-worked (HCW) tubes undergo a cold working process with at least a 35% reduction in thickness of both wall and weld before the final anneal. Filler materials are prohibited during welding, and the weld must undergo 100% radiographic inspection in accordance with ASME standards.
  4. Sanitary pipes may be furnished as hot finished or cold finished, at the manufacturer's discretion.

Hot-Treatment Methods

All materials for ASTM A270 tubing must undergo hot treatment. However, exceptions apply for duplex stainless steel materials such as S31803, S32003, S320205, S32750, N08926, and N08367. In these cases, the material must be heated to a minimum temperature of 1900 ℉ (1040 ℃) and then quenched in water or rapidly cooled by alternative means.

Chemical Composition 

Table : Transposed Chemical Composition of ASTM A270 Stainless Steel Tubing

ElementCarbon, maxManganese, maxPhosphorus, maxSulfur, maxSilicon, maxNickelChromiumMolybdenumNitrogenCopper
S327500.0301.200.0350.0200.806.0-8.024.0-26.03.0-5.00.24-0.320.50 max
S320030.0302.000.0450.0301.004.5-6.520.0-22.03.0-4.00.18-0.250.75 max

Mechanical Tests

Mechanical testing for ASTM A270 stainless steel tubing includes a range of assessments such as negative flattening tests, hydrostatic tests, or nondestructive electric tests. The mechanical strength requirements are specified in Table 2 of the ASTM A270 standard specification.

Table : Mechanical Strength Specifications for ASTM A270 Stainless Steel Tubing

GradeUNSTensile Strength (min, ksi)Yield Strength (min, ksi)Elongation in 2 in. (min, %)Rockwell Hardness Number (max)
TP304S3040075 (515 MPa)30 (205 MPa)35B90
TP304LS3040370 (485 MPa)25 (170 MPa)35B90
TP316S3160075 (515 MPa)30 (205 MPa)35B90
TP316LS3160370 (485 MPa)25 (170 MPa)35B90
2205S3180390 (620 MPa)65 (450 MPa)25C30.5
2507S3220595 (655 MPa)70 (485 MPa)25C30.5
2003S32750116 (800 MPa)80 (550 MPa)32C32

These mechanical strength specifications ensure that the stainless steel tubing meets the required standards for tensile strength, yield strength, elongation, and hardness, ensuring its suitability for various applications in industries such as dairy, food processing, and bio-processing equipment.

Surface Specifications

When it comes to the surface of rolled products, there's no need for extra polishing or smoothing treatments. We're talking about that raw, mill finish—no additional polishing or operations to make it smooth.

Now, if you're looking for a more refined surface, mechanical polishing might be the way to go. Purchasers can specify the level of polish they want using abrasive grit numbering. For instance, Finish No. 80 means the product has been polished with an abrasive media impregnated with No. 80 grit, resulting in a specific ground finish. Similarly, Finish No. 120, 180, and 240 correspond to their respective grit sizes, offering varying degrees of smoothness. Of course, there's room for negotiation between the purchaser and the manufacturer for other mechanically polished finishes.

But wait, there's more! Electrolytic polishing is another option available. Before diving into this process, the manufacturer may opt for different methods to polish the products. And customers have the power to specify the maximum roughness for internal, external, or both surfaces. The surface furnishment—whether it's internal, external, or something like SF4 or SF3—is usually decided upon by mutual agreement between the manufacturer and purchaser.

Marking Matters

When it comes to marking, it's all about compliance. According to A 1016/A1016M, the marking should be in line with what's specified in the order. This includes details for sanitary stainless steel pipes manufactured either seamlessly (SML), welded (WLD), or heavily cold worked (HCW).

Packaging Protocol

Before delivery, it's important to ensure that all steel pipes are bundled securely and covered, whether with paper, cloth, or packed neatly in boxes by the manufacturer.

Extra Requirements

Now, if there are any additional requirements specified in the order, such as intergranular corrosion tests, the manufacturer needs to conduct these tests on representative specimens in their as-shipped condition. Sanitary stainless steel pipes and tubes must be capable of passing these corrosion tests in their original condition. For austenite alloy steel, meeting the Practice E of standard A262 is the benchmark, while for duplex alloy steels like S31803, S32205, and A32750, compliance with experiment C of Test Methods A 923 is necessary.

Special Cases: ASTM A270 Stainless Steel Pipes

For pharmaceutical quality applications, ASTM A270 sets the bar higher, especially concerning chemical composition, strengths, and size tolerances. It's all about ensuring the utmost quality and safety for these specialized applications.To make things clearer, let's delve into some comparative data:

Surface TreatmentDescription
Mill FinishSurface without extra polishing or smoothing treatment.
Mechanical PolishVarious finishes achieved using different abrasive grit sizes: No. 80, No. 120, No. 180, No. 240, and others as agreed upon.
Electrolytic PolishFurther polishing method, following other surface treatments if used.
Other TreatmentsSurface furnishment such as Internal, External, SF4, SF3, etc. as mutually decided.

Such detailed specifications and meticulous testing ensure that the steel products meet the required standards, whether for general use or specialized applications like pharmaceuticals.

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