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Last updateThu, 27 Jul 2017 5pm

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How to Choose the Best Rapid Prototyping Method

How to Choose the Best Rapid Prototyping Method

As new products are designed, including ...

Monitoring Valve Health via the Internet

Monitoring Valve Health via the Internet

Most valve end users are already using s...

Valves in Oxygen Service

Valves in Oxygen Service

In his presentation at VMA’s 2017 ...

Thermal Spray Coating

Thermal Spray Coating

Q: What are the pros and cons of us...

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The Actuation Selection Process

The Actuation Selection Process

Tuesday, 25 July 2017  |  Carlos Gamero

A common misconception in our industry is that actuating a valve is as simple as putting the most cost-efficient actuator on top of your valve of choi...

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Industry Headlines

Wolseley Industrial Group Names Daniel Hogge District Manager

8 HOURS AGO

Daniel Hogge has been appointed district manager of Wolseley Industrial Group’s Mid-Atlantic region, which includes Georgia, South Carolina and North Carolina and most of Florida and Virginia. Effective Aug. 1, Hogge will be responsible for managing the financial results of Wolseley Industrial G...

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TAQA Awards Schlumberger EPCIC Contract for Otter Field

1 DAY AGO

OneSubsea, a Schlumberger company, has been awarded an engineering, procurement, construction, installation and commissioning (EPCIC) contract for a subsea multiphase boosting system by TAQA for the Otter field in the UK North Sea. OneSubsea leverages Cameron flow control, process technologies and m...

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U.S. Crude Oil Production to Reach Record High in 2018

11 HOURS AGO

In EIA’s latest Short-Term Energy Outlook (STEO), total U.S. crude oil production is forecast to average 9.3 million barrels per day (b/d) in 2017, up 0.5 million b/d from 2016. In 2018, EIA expects crude oil production to reach an average of 9.9 million b/d, which would surpass the previous rec...

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Shale Sector to Be Cash Flow Positive by 2020

1 DAY AGO

The tight oil sector has struggled to generate positive cash flow since 2010. Last year, only one company in the sector posted positive cash flow. But there is light at the end of the tunnel. Wood Mackenzie’s new report " When will tight oil make money? " calculates that the five largest tight oil...

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U.S. Consumer Confidence Rebounds in July

1 DAY AGO

The Conference Board Consumer Confidence Index, which had declined marginally in June (a downward revision), improved in July . The Index now stands at 121.1, up from 117.3 in June. The Present Situation Index increased from 143.9 to 147.8, while the Expectations Index rose from 99.6 last month to 103...

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IHS Market PMI Index Reached Four-Month High in July

2 DAYS AGO

July data revealed a further acceleration in business activity growth across the U.S. private sector. At 54.2, up from 53.9 in June, the seasonally adjusted IHS Markit Flash U.S. Composite PMI Output Index signaled the strongest rate of expansion since January.

The pickup in business activity growth ...

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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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