Selecting the correct plate steel is a foundational decision in petrochemical reactor vessel design. The choice between two common grades—ASTM A516 Gr.70 and ASTM A515 Gr.65—directly impacts safety, performance, and cost.
The primary distinction lies in their intended service and impact properties:
ASTM A516 Gr.70: This is a pressure vessel quality (PVQ) steel, specified primarily for lower-temperature service. Its key advantage is guaranteed notch toughness (impact testing) at specified temperatures (e.g., -20°F / -30°C per ASME), making it critical for vessels subject to shock loading or cyclic service in ambient or refrigerated environments.
ASTM A515 Gr.65: This is a higher-temperature carbon steel, designed for intermediate and elevated-temperature service (typically up to ~800°F / 425°C). It is silicon-killed for stability at temperature but is generally not required to meet notch toughness standards unless specified.
For Petrochemical Reactors, the decision hinges on your operating parameters:
Choose
A516 Gr.70 (SA-516 Gr.70) when the reactor operates at or near ambient temperature or requires high impact resistance due to process conditions, pressure cycling, or location. It is the default, safer choice for most general-purpose reactors.
Choose
A515 Gr.65 (SA-515 Gr.65) specifically when the reactor operates at sustained elevated temperatures (e.g., many hydrotreating or catalytic processes) and where post-weld heat treatment (PWHT) will be applied. It offers better cost-effectiveness for high-temperature service.
