NACE International (now part of ) maintains the copyright for this standard.
To evaluate resistance to cracking under specific stress levels.
The standard specifies that FRP pipes must consist of:
Subsea engineering firms use NACE RP0391 during the initial Front-End Engineering Design (FEED) phase. Compliance ensures that equipment achieves a design life often exceeding 20 to 30 years without intervention. Regulatory bodies globally reference this standard during safety audits of offshore platforms.
for different concentrations of acid (e.g., 90%, 93%, 98%). nace rp 0391 pdf
: It details the use of carbon steel , which is common for 93% concentration but warns of its limits. Above 99.5% concentration, carbon steel becomes significantly more vulnerable to corrosion.
In the world of industrial materials engineering, corrosion is the silent enemy that drains budgets, shuts down plants, and creates safety hazards. For facilities dealing with concentrated sulfuric acid ($H_2SO_4$), this enemy is particularly aggressive. This is where (now standardized as NACE SP0391 ) becomes an indispensable tool.
While the original and RP 0391-2001 (Standard Recommended Practice) were the industry benchmarks for years, they have been superseded by SP0391-2016 (Standard Practice).
NACE RP0391-91, titled "Materials for the Handling and Storage of Concentrated Sulfuric Acid and Oleum," is a pivotal Recommended Practice (RP) in the world of corrosion engineering and industrial chemical handling. Published by NACE International (now part of AMPP), this document provides essential guidelines for selecting materials and designing systems that can safely withstand one of the most widely used—and corrosive—chemicals in the world. Scope and Purpose of NACE RP0391 NACE International (now part of ) maintains the
| | Fact (per RP0391) | | :--- | :--- | | "Carbon steel is fine for any concentration of sulfuric acid." | False. RP0391 limits carbon steel to above 90% concentration and ambient temperatures. Below that, corrosion rates skyrocket. | | "Stainless steel is always better." | False. Standard 304/316 stainless can suffer from active corrosion in stagnant concentrated acid. The standard specifies passive alloys only under specific flow conditions. | | "The standard ignores temperature." | False. RP0391 is explicit about the 32°F to 120°F range. Above 120°F, different materials (e.g., high-silicon iron, tantalum) are required. | | "Old copies are fine." | False. The standard has been reaffirmed and revised. Always use the "SP" version to get the latest data on alloy availability. |
: Design must account for the continuous generation of hydrogen gas, which can be an explosion hazard if trapped.
NACE SP0391 divides asset architectures into specific material categories based on velocity, mechanical stress, and maintenance cycles. 1. Carbon Steel
Concentrated sulfuric acid (90%-100%) at ambient temperatures only. Compliance ensures that equipment achieves a design life
Because sulfuric acid is hygroscopic (absorbs moisture from the air), storage tanks must be sealed. Moisture dilution at the surface of 98% acid can turn it into highly corrosive, lower-concentration acid, damaging the tank roof and vents. NACE RP0391 vs. Other Standards
: Typically kept under 2 to 3 feet per second (0.6 to 0.9 m/s) for carbon steel.
Yes, provided the resin is hydrocarbon-resistant. The standard covers FRP for hydrocarbon service, but check for specific fuel-grade additives.
Materials for handling and storing commercial concentrated sulfuric acid. Concentration Range: 90% to 100%
This is the section most often cited in failure analysis. NACE RP 0391 explicitly prohibits: