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Young Valve Professionals: Logan Moore

Young Valve Professionals: Logan Moore

In 2014, VMA's leadership created the Va...

VALVE Magazine: Readers' Choice 2017

VALVE Magazine: Readers' Choice 2017

Happy New Year to our VALVE Magazine rea...

Educational Opportunities Abound at New VMA Knowledge Forum

Educational Opportunities Abound at New VMA Knowledge Forum

From technical to manufacturing to human...

Offshore Production in a Low Oil-Price Environment

Offshore Production in a Low Oil-Price Environment

Three years ago, The Washington Post publi...

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Industry Headlines

Emerson Completes Acquisition of ProSys, Inc.

Thursday, 18 January 2018  |  Chris Guy

Emerson has acquired ProSys Inc., a global supplier of software and services that increase production and safety for the chemical, oil & gas, pulp &...

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Interior Coatings for Waterworks Valves

Interior Coatings for Waterworks Valves

Monday, 15 January 2018  |  John V. Ballun, P. E.

Since the 1990s, two types of epoxy coatings have been commonly specified and used for iron valves in the waterworks industry: fusion-bonded epoxy and...

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Industry Headlines

Emerson Completes Acquisition of ProSys, Inc.

10 HOURS AGO

Emerson has acquired ProSys Inc., a global supplier of software and services that increase production and safety for the chemical, oil & gas, pulp & paper and refining industries. ProSys complements Emerson’s May 2017 acquisition of MYNAH Technologies, which provides simulation and opera...

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ASCO Valve and Numatics Now Doing Business as ASCO, L.P.

2 DAYS AGO

Effective January 1, 2018, ASCO Valve, Inc. and Numatics, Inc. began doing business as ASCO, L.P. This change in legal entities affects neither current channel alignment nor purchasing processes—everything will remain the same, including product authorizations. Within ASCO, a business unit of Em...

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EIA Predicts Record U.S. Fossil Fuel Production

11 HOURS AGO

In its January 2018 Short-Term Energy Outlook, the U.S. Energy Information Administration (EIA) forecasts that total fossil fuels production in the U.S. will average almost 73 quadrillion British thermal units (Btu) in 2018, the highest level of production on record. EIA expects total fossil fuel prod...

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TransCanada Proceeding with Keystone XL Pipeline

12 HOURS AGO

TransCanada Corp. has successfully concluded the Keystone XL open season, securing approximately 500,000 barrels per day of 20-year commitments, positioning the proposed project to proceed . Interest in the project remains strong and TransCanada will look to continue to secure additional long-term con...

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U.S. Industrial Output Rose 0.9% in December

15 HOURS AGO

Industrial production rose 0.9% in December even though manufacturing output only edged up 0.1%. Revisions to mining and utilities altered the pattern of growth for October and November, but the level of the overall index in November was little changed. For the fourth quarter as a whole, total indus...

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Beige Book: Modest to Moderate Growth Prevalent Across U.S.

15 HOURS AGO

According to the Federal Reserve Beige Book, reports from the 12 districts indicated that the economy continued to expand from late November through the end of the year, with 11 districts reporting modest to moderate gains and Dallas recording a robust increase. The outlook for 2018 remains optimistic...

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NACE MR0103 and Duplex Stainless Steels

materials_q_and_a_graphicQ: Why are some suppliers reluctant to produce duplex stainless-steel valves that are compliant with NACE MR0103?

 

A: Duplex stainless steels are those that are chemically balanced to provide a target microstructure of 50% austenite phase and 50% ferrite phase. Duplex stainless-steel valves required to meet NACE MR0103 will almost always be installed in a sour, corrosive, chloride-containing environment, so it is essential the material provides optimized resistance to sulfide stress cracking, chloride stress corrosion cracking, chloride pitting and general corrosion.

 

The task group that created the NACE MR0103 document, “Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments,” recognized that microstructure is a key factor influencing the properties of duplex stainless steel. They also recognized that the microstructure is influenced strongly by chemistry and by heating and cooling during processing of the material. As a result, NACE MR0103 includes some very stringent requirements for duplex stainless steels, especially with regard to welding. Since most valve bodies (and many bonnets) are produced from castings, welding will be performed. Although most welding will be minor and cosmetic in nature, NACE MR0103 does not distinguish between minor and major weld repairs when it comes to welding requirements for these materials.

During welding, the cooling rates that occur in the weld deposit and in the heat-affected zone (HAZ) can have dramatic effects on the final microstructure. Higher cooling rates tend to promote higher ferrite levels, which are advantageous for chloride stress corrosion cracking resistance but detrimental to sulfide stress cracking resistance and impact resistance. Conversely, slower cooling rates promote lower ferrite levels, which will result in increased sulfide stress cracking resistance and toughness, but reduced chloride stress corrosion cracking resistance, and can allow the formation of harmful second phases that detract from the overall corrosion resistance of the material.

Therefore, successful welding of duplex stainless steels to provide optimum properties is a fine balancing act, which requires careful control of welding parameters that affect the cooling rate of the weldment.

Welding Requirements

In order to achieve the necessary control over cooling rates during welding, NACE MR0103 includes several requirements with regard to qualification of welding procedures:

  1. Each procedure qualification specimen must be hardness surveyed using to 10 kg Vickers hardness scale. The readings must average no more that 310 HV 10, and no individual reading is allowed to exceed 320 HV 10.
  2. The ferrite content must be measured metallographically in the weld deposit and HAZ of each procedure qualification specimen. The measured ferrite content must fall within the 35% to 65% range in all measured locations.
  3. The heat input required per the resulting welding procedure specification must not deviate by more than 10% from the heat input used when producing the procedure qualification specimen(s).
  4. The base metal thickness range qualified by a given procedure specimen of thickness T is 0.8T to 1.2T.

 

Requirements 1 and 2, although they add testing over and above the normal ASME Section IX requirements, are not overly problematic.

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