ASTM A213 Pressure Rating

For engineers and procurement specialists sourcing stainless steel heat exchanger tubes, understanding ASTM A213 pressure rating is essential. Pressure ratings determine how much internal pressure a tube can safely withstand under specific temperature conditions. Selecting the correct tube specification directly affects heat exchanger safety, lifespan, and operational efficiency.

This guide explains ASTM A213 pressure ratings, calculation methods, common stainless steel grades, and key flow considerations that buyers should evaluate when purchasing heat exchanger tubing.

 

1.What is ASTM A213 material?

ASTM A213 is a widely used international specification covering seamless ferritic and austenitic alloy-steel boiler, superheater, and heat exchanger tubes.

For stainless steel heat exchanger applications, the most common grades include:

ASTM Grade	Equivalent Grade	Key Features	Typical Applications
TP304	1.4301 / SUS304	Good corrosion resistance, economical	General heat exchangers
TP304L	1.4306	Lower carbon, better weldability	Food processing heat exchangers
TP316	1.4401	Improved corrosion resistance	Chemical equipment
TP316L	1.4404	Low carbon + excellent corrosion resistance	Marine and chemical heat exchangers
TP321	1.4541	Stabilized with Ti for high temperature	High-temperature heat exchangers

Among these, TP316L heat exchanger tubes are widely used in chemical plants, seawater desalination systems, and condensers because of their superior resistance to pitting and crevice corrosion.

 

 

2.ASTM A213 316L Pressure Rating Chart (Reference)

Below is a reference table for ASTM A213 TP316L seamless tubes at room temperature (approx. 20°C/70°F).
Values are based on an allowable stress of 16,700 PSI (as per ASME BPVC).

Outside Diameter (OD)	Wall Thickness (BWG/mm)	Working Pressure (PSI)	Burst Pressure (Theoretical PSI)
1/2" (12.7 mm)	18 (1.24 mm)	3,250	13,000
1/2" (12.7 mm)	16 (1.65 mm)	4,300	17,200
3/4" (19.05 mm)	16 (1.65 mm)	2,850	11,400
3/4" (19.05 mm)	14 (2.11 mm)	3,700	14,800
1" (25.4 mm)	16 (1.65 mm)	2,150	8,600
1" (25.4 mm)	12 (2.77 mm)	3,650	14,600

Disclaimer: These values are for reference only. For actual design, a safety factor (typically 4:1) and temperature derating factors must be applied.

 

shell and tube heat exchanger with stainless steel tubes

3.How is the ASTM A213 Pressure Rating Calculated?

The internal pressure rating for stainless steel tubing is generally calculated using Barlow's Formula. This formula relates the internal pressure to the allowable stress of the material, its thickness, and its diameter.

The Formula:

P = Internal Design Pressure (PSI or MPa)

S = Allowable Stress Value (from ASME B31.3 or BPVC Section II)

t = Nominal Wall Thickness (Inches or mm)

D = Outside Diameter (OD) (Inches or mm)

Note for Buyers: ASTM A213 specifies Minimum Wall Thickness. When calculating for safety, always ensure you account for the manufacturing tolerance (usually +20% / -0%).

 

4.The Impact of Temperature on Pressure Rating

As the operating temperature of a boiler or heat exchanger increases, the strength of the stainless steel decreases. This is vital for ASTM A213 applications.

At 200°C (392°F): The allowable stress of 316L drops to roughly 85% of its room-temperature value.

At 400°C (752°F): The strength drops to approximately 70%.

Procurement Tip: Always provide your supplier with the maximum operating temperature so they can verify the derated pressure capacity.

 

5.Dimensions of Heat Exchanger Tubes ASTM A213

ASTM A213 seamless heat exchanger tubes typically feature outside diameters (OD) ranging from 1/8 inch (3.2 mm) to 5 inches (127 mm), with wall thicknesses between 0.015 and 0.500 inches (0.4 to 12.7 mm). The most common OD sizes for heat exchangers are 19.05 mm (3/4") and 25.4 mm (1").

Outside Diameter	Wall Thickness Range	Length
12.7 mm (1/2")	0.7 – 2.0 mm	Up to 24 m
19.05 mm (3/4")	1.0 – 3.0 mm	Up to 24 m
25.4 mm (1")	1.2 – 3.5 mm	Up to 24 m
38.1 mm (1.5")	1.5 – 4.0 mm	Up to 24 m

 

 

6.Flow Rate Considerations for Heat Exchanger Tube

In addition to withstanding pressure, tubing must also be capable of accommodating fluid flow. For heat exchanger purchasers, two issues closely related to fluid flow are of critical importance: A. Optimal flow velocity, and B. Pressure drop (ΔP).

A. Optimal Flow Velocity

If the flow velocity is too high, it causes erosion-corrosion, especially in the U-bends of heat exchangers.

Fluid Type	Recommended Velocity
Cooling water	1.0 – 2.5 m/s
Seawater	1.0 – 2.0 m/s
Oil	0.5 – 1.5 m/s
Steam condensate	20 – 40 m/s

If the flow velocity is too high, it causes erosion-corrosion, especially in the U-bends of heat exchangers.
Risk: Exceeding 3.5 m/s in liquid service can strip the protective chromium oxide layer from 316L tubes.

 

B. Pressure Drop 

Pressure drop is the loss of pressure as fluid travels through the tube due to friction.

Narrower Tubes (Smaller ID): Increase heat transfer efficiency but significantly increase pressure drop, requiring more pumping power.

Surface Roughness: ASTM A213 seamless tubes have a smoother internal surface than welded tubes (A249), resulting in a lower pressure drop and better resistance to fouling.

 

7. Example Flow Capacity of Heat Exchanger Tubes

Tube Size	Internal Diameter	Flow Velocity	Approx Flow Rate
19.05 × 1.65 mm	15.75 mm	2 m/s	0.39 m³/h
25.4 × 2.11 mm	21.18 mm	2 m/s	0.72 m³/h
38.1 × 2.77 mm	32.56 mm	2 m/s	1.66 m³/h

These values help engineers estimate pump requirements and heat exchanger capacity.

 

ASTM A213 Tubing Procurement Checklist

When submitting an inquiry, please clearly specify the following parameters to ensure that the pressure rating meets your specific requirements:
Material Grade: (e.g., TP316L, TP304, TP321).
Supply Condition: Seamless (ASTM A213 standard tubing is exclusively seamless).
Dimensions: Outside Diameter × Minimum Wall Thickness (e.g., 19.05 mm × 2.11 mm minimum wall thickness).
Testing Requirements:
Hydrostatic Test: Mandatory; used to verify the pressure integrity of the tubing.
Eddy Current Testing: Used to detect wall thinning or crack defects.
Heat Treatment: Ensure a "Solution Annealed" condition to achieve optimal corrosion resistance and ductility.

Click to obtain the ASTM A213 Heat Exchanger Tube Quality Inspection Report.