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The VMA Knowledge Forum, Part One: Technology at the Forefront

The VMA Knowledge Forum, Part One: Technology at the Forefront

The first VMA Valve Industry Knowledge F...

Air Valves in Piping Systems

Air Valves in Piping Systems

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Are Valves from Low-Cost Countries Getting Better?

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Managing the Generation Gap: Much Ado About Nothing?

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Industry Headlines

Chemical Activity Trends Suggest Growth into Early 2019

Wednesday, 25 April 2018  |  Chris Guy

The American Chemistry Council's Chemical Activity Barometer slipped 0.1% in April to 121.6% on a three-month moving average (3MMA) basis. This follow...

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Industry Headlines

Val-Matic Names Andrew Brudniak Project Manager

1 DAY AGO
Val-Matic Names Andrew Brudniak Project Manager

After four years with Val-Matic Valve & Mfg. Corp. , Andrew Brudniak was recently promoted to project manager, after having recently held the position of sales engineer for the northeast territory.

Brudniak also has passed the exam for the Project Management Professional (PMP) certification offered...

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Weir Group Plans to Sell Flow Control Division

5 DAYS AGO

The Weir Group’s board of directors will initiate a process to sell the Flow Control division. This process will focus on maximizing value for shareholders, with all options to be considered and no fixed timetable. Proceeds will be used to further reduce leverage and to fund future investment in...

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Chemical Activity Trends Suggest Growth into Early 2019

18 HOURS AGO

The American Chemistry Council's Chemical Activity Barometer slipped 0.1% in April to 121.6% on a three-month moving average (3MMA) basis. This follows six consecutive monthly gains and a dip from the barometer’s highest point since modeling began. The barometer remains up 3.8% on a 3MMA compa...

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Formosa Selects Louisiana for $9.4B Petrochemical Project

20 HOURS AGO

Formosa Petrochemical Corp. has selected St. James Parish in Louisiana for a $9.4 billion chemical manufacturing complex and has purchased a 2,400-acre site along the west bank of the Mississippi River.

Located just downriver from the Sunshine Bridge, the complex would be built in two phases and prod...

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40% of Small Manufacturers Likely to Add Staff this Year

21 HOURS AGO

Xometry released the findings of its quarterly Small Manufacturing Index, showing that 40% of small manufacturers surveyed are likely to hire more employees this year as business confidence has risen from a year ago. Additionally, 28% of those surveyed stated they have hired more employees since Q1 20...

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IHS Markit U.S. Manufacturing Index Rose in April

1 DAY AGO

Manufacturers reported the greatest improvement in overall business conditions since September 2014 in April. This was highlighted by the seasonally adjusted IHS Markit Flash U.S. Manufacturing Purchasing Managers’ Index (PMI) rising from 55.6 in March to 56.5.

Stronger growth in new orders drov...

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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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