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Last updateMon, 19 Feb 2018 7pm

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Achieving Predictable Valve Performance for Safety Applications

Achieving Predictable Valve Performance for Safety Applications

A focus on having the proper specificati...

Putting Servo Valves Back to Work

Putting Servo Valves Back to Work

Industries as varied as paper production...

Corrosion and Fouling: Is There a Solution?

Corrosion and Fouling: Is There a Solution?

According to a 1998 study released by the ...

Valves with All the Trimmings

Valves with All the Trimmings

The term valve trim has been around for ...

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Industry Headlines

Strong Momentum for M&A Activity in the Chemical Industry

Monday, 19 February 2018  |  Chris Guy

Global chemical mergers and acquisitions (M&A) activity in 2018 is expected to remain strong, as higher valuations continue to be mitigated by imp...

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Valve Positioners Offer Improved Control Valve Performance

Valve Positioners Offer Improved Control Valve Performance

Monday, 19 February 2018  |  David Matherly

From time to time, we are re-posting well-received or particularly valuable articles that have previously run on VALVEMagazine.com so that those who m...

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Industry Headlines

ValvTechnologies ITC 2018 Recap

3 DAYS AGO

The biennial ValvTechnologies’ International Technical Conference and Users Group (ITC) was held on February 8-9 in Houston. Seeking to educate, inspire and engage attendees over a two-day period, the event brought together hundreds of attendees from across the globe to share valuable insight ...

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Matthew Davis Named Field Service Manager at Weir

4 DAYS AGO

Weir Valves & Controls USA (WVC USA) has appointed Matthew Davis to the position of field service manager. In his new role, Davis will be responsible for managing the WVC USA Field Service crew and organizing WVC Service jobs for power plants worldwide.

Davis joins WVC USA with over 20 years of ex...

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Strong Momentum for M&A Activity in the Chemical Industry

5 HOURS AGO

Global chemical mergers and acquisitions (M&A) activity in 2018 is expected to remain strong, as higher valuations continue to be mitigated by improving global economic conditions, continued inexpensive financing, and an appetite amongst industry participants for growth and transformative M&...

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TransCanada Turns Attention to Natural Gas System

4 DAYS AGO

TransCanada Corp. will move forward with a $1.9 billion expansion of its NGTL System to connect incremental supply and expand basin export capacity by one billion cubic feet of natural gas per day at the interconnection with its Canadian Mainline. NGTL expects to begin construction in 2019.

The increme...

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Construction Starts in 2017 Decline 7%

5 HOURS AGO

Many of the leading U.S. metropolitan areas for commercial and multifamily construction starts showed reduced activity in 2017 compared to levels reported during 2016, according to Dodge Data & Analytics. Of the top ten markets ranked by the dollar amount of construction starts, seven registered...

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Philly Fed: Manufacturing Activity Expanded Solidly

8 HOURS AGO

The index for manufacturing activity in the Philadelphia Federal Reserve region increased 4 points in February to a reading of 25.8. The index has stayed within a relatively narrow range over the past nine months. Nearly 41% of the firms indicated increases in activity this month, while 15% reported...

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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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