What Governs SA516 Gr.70 Thickness Tolerance?
SA516 Gr.70 steel plate is supplied to the dimensional tolerances of ASTM A20/A20M (the general requirements standard for steel plates for pressure vessels). The thickness tolerance defines how much the actual plate thickness may deviate from the specified thickness, and it depends on the specified thickness, the plate width and the ordered condition (for example as-rolled, normalized or quenched and tempered).
Typical Tolerance Rules (Indicative per A20/A20M; Confirm the Current Edition)
Standard tolerance: for carbon steel plates, the thickness tolerance is usually expressed as an allowable deviation (for example ±0.25 mm up to certain thickness ranges), with tighter values for thinner plates and wider plates.
Wide plates: plates over 2 m (and over 3 m) in width carry larger permissible deviations than narrow plates, because of the rolling process.
Plate edge condition: sheared or cut edges and universal-mill edges have different tolerance tables.
Ordering tighter tolerances: tighter-than-standard tolerances can be agreed at the order (often at additional cost); specify the required limits clearly.
As a guide, common SA516 Gr.70 plates are supplied with thickness tolerances such as +0.3/-0.3 mm for thin plates, increasing with thickness and width - always obtain the mill's tolerance table for the exact ordered specification.
Why Tolerance Matters for Pressure Vessels
The plate thickness directly affects the calculated design stress of a pressure vessel: thinner-than-specified plates reduce the safety margin, while thicker plates add cost and weight. Confirming the tolerance class at the order and checking the delivered plates protects both the design and the budget.
SA516 Steel Plate Chemical Composition
|
Element |
Composition (% by weight) |
|---|---|
|
Carbon (C) |
0.27 max |
|
Manganese (Mn) |
0.85–1.20 |
|
Phosphorus (P) |
0.035 max |
|
Sulfur (S) |
0.035 max |
|
Silicon (Si) |
0.15–0.40 |
|
Aluminum (Al) |
0.02 min (for killed steel) |
|
Iron (Fe) |
Balance |
SA516 Steel Plate Mechanical Property
|
Property |
Value |
|---|---|
|
Tensile Strength |
485–620 MPa (70–90 ksi) |
|
Yield Strength (min) |
260 MPa (38 ksi) |
|
Elongation (min, 200 mm) |
17% |
|
Elongation (min, 50 mm) |
21% |
|
Hardness (HB, typical) |
140–200 HB |
|
Impact Toughness (Charpy V-notch) |
Meets ASME requirements at -46°C |
SA516 Steel Plate Typical Applications
High-pressure separators, absorber towers, and hydrocarbon storage vessels.
Petrochemicals: Chemical reactors, heat exchangers, and fractionator columns.
Power Generation: Industrial boilers, steam drums, and condenser units.
Cryogenics: Liquefied natural gas (LNG) storage tanks and low-temperature processing equipment down to -46°C (-50°F).
Storage Systems: API 650 and API 620 large-scale industrial storage tanks.
Why Choose us?
Ample Inventory: Over 5,000 tons of SA516 Gr 70 steel plate in stock, with thicknesses ranging from 6mm to 300mm.
Customized Solutions: Support for custom cutting and bulk orders of A516-70 carbon steel plates for large-scale projects.
Quality Certification: Mill Test Certificates (MTC) and third-party inspections ensure compliance with ASTM A516 Gr 70 standards.
Frequently Asked Questions
Q: What is the standard for SA516 plate thickness tolerance?
A: ASTM A20/A20M, which defines thickness tolerances by specified thickness and width; the applicable tolerance class should be confirmed with the mill.
Q: What are the typical tolerance values for SA516 Gr.70?
A: Typical carbon-plate tolerances range from about ±0.25 mm for thin narrow plates to several millimetres for thick wide plates; consult the A20 table for the exact ordered size.
Q: Can I order a tighter thickness tolerance?
A: Yes, tighter-than-standard tolerances can be negotiated at the order; they usually cost more and may limit the plate size.
Q: How is thickness measured?
A: Per A20 requirements, at defined locations away from the plate edges, with specified measuring instruments; the mill certificate documents the results.
