The NACE Compliant Valve

Been doing this for 40 years, If it’s stainless it meets NACE

Industry old timer

Customer often request NACE compliant valves without the understanding of what it means. a NACE valve needs to meet two standards published through the National Association of Corrosion Engineers (NACE): NACE MR0175/ISO 15156 and NACE MR0103/ISO 17945. This two specifications guide people on the identification of both when and what material is needed. With multiple revisions since the original revision, we have came a long way since the saying “If it’s stainless it meets NACE”. We should try to expand beyond the basic of valve material.

TLDR

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Why NACE Compliant?

The oil and gas industry have experienced “unscheduled releases” in the field due to various material failures. Engineers and scientist have determined the mechanisms leading to some of these failures and developed guidance surrounding these experience in the selection and manufacturing of products which can be resistant against these failure mechanisms.

H2S Corrosion / Wet H2S Cracking

“Sour” Service is typically understood to be situations where material is exposed to a relative high percentage of H2S. In these environments, materials can be attacked by the hydrogen available in the media leading to failure and cracking of these material. The hydrogen atoms preferentially seep into the area around hard material and microstructures, such as around welded material which have not been stress relieved.

Sulfide Stress Cracking (SSC)

The Below factors of the EXPOSED material contributes to SSC.

• Chemical Composition
• Strength (Hardness): the harder, the more likely. Primary parameter
• Heat Treatment: Affects grain structure, stress, strength, and hardness
• Microstructure
• Internal residual tensile stress

The below is Process and Environmental Factors which contributes to SSC

• Total tensile stress applied to the material
• Hydrogen flux in the exposed material: Details explanation within NACE documents
• Temperature: Higher more susceptible to hydrogen infusion (While wet), cracks at Ambient
• Exposure Time

Other Mechanisms

Other primary mechanism of hydrogen based failure of material are Hydrogen Blistering, Hydrogen-Infused Cracking (HIC), and stress-oriented hydrogen-induced cracking (SOHIIC). those will be discussed in a different article.

Complying to NACE MR0103: 2015

Using Table 1 within the standard, it presents a “Road Map” which guides the reader on what sections are applicable to the material group in question in the following categories

• Heat Treatment Condition
• Additional Material Requirements
• Additional Fabrication Requirements

Examples

Let’s take a very common Example of ASTM A216-WCB Carbon steel gate valve in Trim 8. The valve typically will have 3 main components exposed to the media. ASTM A216-WCB, ASTM A182-F6a, ASTM A105N, and Bolting Material, Typically ASTM A193 B7

• Shell: ASTM A216-WCB (P-No. 1, Group 2) and ASTM A105N (P-No. 1, Group 2)
  • The valve will have to be in one of the 6 allowable heat treatment condition
  • Base metal hardness controls not required
  • Welding shall be controlled (Including Repair) 15.3, NACE SP0472
    • Overlay Welding 15.2, 15.4, NACE SP0472
    • Spray Cladding (Wedge Guides), base material not to exceed lower transformation temperature during spraying NACE SP0472
  • If piping bend is used, such as bypass piping, needs to be heated bend and hardness control the bended area to 225 HBW
• Stem: ASTM A182-F6a (P-No. 6, Group 1 or 3)
  • Heat treatment specified. Austenitize and double tempered. (3 step process)
  • Hardness limited to 22 HRC
• Fastener: ASTM A193 B7 | ASTM A194 2H
  • If “Exposed” to environment, ASTM A193 B7M and ASTM A194 2HM to be used
• If spring is used, typically Inconel X-750 Spring is selected, max Hardness 50 HRC

NACE SP0472 15th Edition, August 17, 2020

It should be noted that NACE SP0472 was published in 2020 and is a necessary standard for manufacture to know how to stay in compliance to NACE. A further article will review this standard in detail.

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