02122016Fri
Last updateThu, 11 Feb 2016 3pm

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Introduction to Pressure Relief Devices - Part 1

Introduction to Pressure Relief Devices - Part 1

When the pressure inside equipment such ...

Is Your Company Ready for The New Reality?

Is Your Company Ready for The New Reality?

Since August, 2015, when VMA’s 201...

Offshore Oil Extraction and Transportation

Offshore Oil Extraction and Transportation

Offshore oil facilities come to the fore...

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Industry Headlines

MRC Global Signs Agreement to Sell OCTG Business

12 HOURS AGO  |  Chris Guy

MRC Global Inc. has entered into a definitive agreement to sell its U.S. Oil Country Tubular Goods (OCTG) business to Sooner Pipe, LLC, a subsidiary o...

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Industry Headlines

MRC Global Signs Agreement to Sell OCTG Business

12 HOURS AGO

MRC Global Inc. has entered into a definitive agreement to sell its U.S. Oil Country Tubular Goods (OCTG) business to Sooner Pipe, LLC, a subsidiary of Marubeni-Itochu Tubulars America, Inc., for $48 million, subject to certain adjustments.

MRC Global's U.S. OCTG sales were approximately $305 milli...

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PM International Suppliers Joins VMA

1 DAY AGO

This week VMA welcomes PM International Suppliers, LLC as our newest associate member (distributor/channel partner), our 2nd new member of 2016 so far.

PM International supplies pipe and fittings, tubing, valves, flanges, bars, sheet and forgings with numerous worldwide sources for a wide variety o...

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IHS: North American Drillers Need Billions More in Cuts

1 DAY AGO

The depressed oil price environment is painting a gloomy outlook for North American exploration and production (E&Ps) companies, and further, significant CAPEX cuts are needed in order for the group to demonstrate real financial discipline and align spending more closely with cash flow, accordin...

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Energy Sector Bracing for More Bankruptcy Filings in 2016

1 DAY AGO

“In 2015, the energy sector accounted for more than one-half of all public company bankruptcy filings, including eight of the 10 largest filings. Current oil prices and bond values indicate that 2016 will be another active year,” according to McGuireWoods Consulting.

“To account f...

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U.S. Job Openings Climb to Second-Highest Level on Record

2 DAYS AGO

The number of job openings increased to 5.6 million in December, the second highest number ever recorded, the U.S. Bureau of Labor Statistics reported today. Hires and separations were little changed at 5.4 million and 5.1 million, respectively. Within separations, the quits rate was 2.1%, and the l...

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Machine Tool Orders Rose in December, Down in 2015

2 DAYS AGO

The U.S. Manufacturing Technology Orders report for December 2015 showed that order values grew 20.4% compared to the prior month, according to The Association for Manufacturing Technology (AMT). For all of 2015, the year’s total orders were down 17.4% compared to 2014.

While the month-to-mon...

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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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