The keyword "NACE RP 0391 PDF" refers to a critical industrial standard practice published by NACE International (now part of AMPP) titled "Materials for the Handling and Storage of Commercial Concentrated (90 to 100%) Sulfuric Acid at Ambient Temperatures."
This standard, last majorly revised as NACE Standard RP0391-2001 and later redesignated as SP0391, provides essential guidelines for engineers and maintenance personnel in the chemical processing industry to prevent catastrophic failures and manage the extreme corrosivity of concentrated sulfuric acid. 1. Scope and Objective
The primary objective of NACE RP 0391 is to provide a consensus-based framework for the selection of materials and the design of equipment used to handle concentrated sulfuric acid.
Concentration Range: It specifically covers acid strengths between 90% and 100% by weight.
Temperature Limit: "Ambient" temperatures are defined as those up to 50°C (120°F), accounting for solar heating in tropical climates.
Applicability: The standard is intended for stationary storage tank systems, including internal piping and associated recirculation loops. 2. Carbon Steel: The Primary Material
A significant portion of NACE RP 0391 focuses on the use of carbon steel, which is the most common material for concentrated sulfuric acid storage due to its cost-effectiveness and the formation of a protective ferrous sulfate ( FeSO4cap F e cap S cap O sub 4 ) film.
Corrosion Mechanism: When carbon steel contacts concentrated acid, it initially corrodes but quickly forms an insoluble sulfate layer that limits further attack.
Velocity Restrictions: This protective film is fragile. The standard recommends maintaining acid flow velocities below 0.9 m/s (3 ft/s) to prevent "velocity-accelerated corrosion" where the film is physically stripped away.
Hydrogen Grooving: A specific localized attack mentioned in the standard is "hydrogen grooving," caused by the movement of hydrogen bubbles along vertical walls, which prevents the stable formation of the protective film. 3. Key Design and Maintenance Requirements
NACE RP 0391 outlines several technical requirements to ensure the mechanical integrity of acid systems: nace rp 0391 pdf
Welding and Fabrication: All weldments must be thoroughly inspected for defects like slag, porosity, or laps, as these can initiate rapid localized corrosion.
Hydrogen Venting: Design must account for the continuous generation of hydrogen gas, which can be an explosion hazard if trapped.
Moisture Control: Because sulfuric acid is highly hygroscopic (it absorbs water from the air), storage systems must include desiccant dryers on vents to prevent the acid from diluting. Diluted acid (below 77%) is far more corrosive to carbon steel. 4. Comparison with Related Standards
While NACE RP 0391 focuses on materials selection, it is often used in conjunction with other standards:
NACE SP0294: Specifically covers the design, fabrication, and inspection of sulfuric acid storage tanks.
NACE SP0592: Provides procedures for applying internal coating systems to railroad tank cars used for acid transport. 5. Accessing the NACE RP 0391 PDF
As this is a copyrighted technical document, it is not legally available for free download. Official copies can be purchased through authorized distributors:
ANSI Webstore: Offers preview pages and full PDF purchase for the 2001 version.
AMPP (formerly NACE) Store: The official source for the most current edition, now listed as SP0391.
Intertek Inform: Provides historical and current versions of the standard. ANSI Webstorehttps://webstore.ansi.org NACE Standard RP0391-2001 - ANSI Webstore The keyword "NACE RP 0391 PDF" refers to
NACE RP0391 (now updated to NACE SP0391 ) is a standard recommended practice titled
"Materials for the Handling and Storage of Commercial Concentrated Sulfuric Acid at Ambient Temperatures"
. It is primarily used by engineers and maintenance personnel in the chemical process industries to select safe, cost-effective materials for systems handling sulfuric acid.
AMPP - The Association for Materials Protection and Performance Scope and Application Acid Concentration:
Covers commercial concentrated sulfuric acid in the range of 90% to 100% Temperature: Designed for ambient temperatures 50°C (120°F) , which accounts for solar heating in tropical climates. Excluded Media:
This standard does not apply to acid concentrations below 90% or temperatures exceeding 50°C. GlobalSpec Key Technical Guidance Material Selection:
Provides guidance on using carbon steel, stainless steels, and various alloys. Corrosion Phenomena: Addresses specific risks like hydrogen grooving
in pipelines and tank walls, as well as the effects of flow velocity on iron-based alloys. Protective Measures: Discusses methods like anodic protection
for carbon steel to reduce corrosion and maintain acid purity. Linings and Coatings:
Includes information on high-temperature baked phenolic coatings and the use of plastics like PVC, PVDF, and polyethylene for specific concentrations. GlobalSpec Standard Evolution Original Issue: First prepared in 1991 as Major Revision: Revised in 2001 as RP0391-2001 Current Active Version: The standard was reaffirmed and renamed to SP0391-2016 Taper grinding damaged area (12:1 length:depth ratio)
AMPP - The Association for Materials Protection and Performance Accessing the PDF Official copies are intellectual property of
(formerly NACE International). You can obtain the official document through these sources: AMPP Store The primary source for the active SP0391 standard. ANSI Webstore
Offers the RP0391-2001 version in electronic Adobe Acrobat PDF format. ANSI Webstore safety procedures mentioned in this standard?
The standard emphasizes that no lining performs well on a poorly prepared surface. For steel, this usually means Near-White Metal blast cleaning (SSPC-SP 10) or White Metal (SSPC-SP 5). For concrete, specific moisture content and surface profile requirements are detailed to ensure adhesion.
Unlike steel, FRP repairs are laminated in the field. The standard specifies:
Since 2021, NACE International has merged with SSPC to form AMPP. The official document is now AMPP SP0391-2022 (the latest revision).
NACE RP 0391 (Revised as NACE SP0391, now AMPP SP0391) stands for: "Standard Practice—Materials, Fabrication, and Handling of Fiberglass-Reinforced Plastic (FRP) Pipelines for Onshore Corrosive Service."
Originally published by NACE Task Group T-5A, this recommended practice was created to fill a critical gap: while FRP pipes are highly resistant to corrosion (unlike steel), they are vulnerable to improper handling, poor installation, and UV degradation. The standard provides a systematic methodology to ensure FRP pipelines achieve their intended 20–50 year design life.
Understanding the standard is one thing; applying it is another. Here are three real-world scenarios where consulting the nace rp 0391 pdf is mandatory.
One of the most valuable parts of the PDF is the guidance on inspection. It defines how to check for holidays (pinholes), thickness, and adhesion. Because these linings are often applied in thick films, standard inspection methods for thin-film paints may not apply.
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