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Industry Headlines

Additive Manufacturing Industry Hit $5.1 Billion in 2015

-1 DAYS AGO  |  Chris Guy

According to Wohlers Report 2016, the additive manufacturing (AM) industry, consisting of all AM products and services worldwide, grew 25.9% (CAGR) to...

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Industry Headlines

Weir Opens New Safety Relief Valve Facility in Malaysia

21 HOURS AGO

Weir has opened a new facility to increase the global reach and competitiveness of Weir valves by establishing a manufacturing and assembly plant close to Malaysia’s capital Kuala Lumpur.

The Malaysian operation has already successfully supplied several large and strategic projects, especially ...

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ValvTechnologies Names Garcia, Mermelstein to New Positions

5 DAYS AGO
ValvTechnologies Names Garcia, Mermelstein to New Positions

ValvTechnologies, Inc. has named David Garcia director of manufacturing and Steve Mermelstein as regional director, Americas and director, channel management.

Previously, West Point graduate Garcia served as director of operations for Merla Wellhead Solutions and held plant manager positions at Hallib...

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What’s Behind Growth of U.S. Natural Gas Use

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U.S. consumption of natural gas is projected to rise from 28 trillion cubic feet (Tcf) in 2015 to 34 Tcf in 2040, an average increase of about 1% annually, according to EIA's Annual Energy Outlook 2016 . The industrial and electric power sectors make up 49% and 34% of this growth, respectively, while ...

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Industry Survey Finds U.S. Wind Power on the Rise

-1 DAYS AGO

Wind power, America’s fastest growing new source of electricity, will stay on pace to grow to supply 10% of U.S. electricity by 2020, that’s according to the American Wind Energy Association (AWEA). Helping to grow wind energy in the U.S. are a mix of stable federal policy, passed late las...

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Additive Manufacturing Industry Hit $5.1 Billion in 2015

-1 DAYS AGO

According to Wohlers Report 2016, the additive manufacturing (AM) industry, consisting of all AM products and services worldwide, grew 25.9% (CAGR) to $5.165 billion in 2015. The CAGR for the previous three years was 31.5%. Over the past 27 years, the CAGR for the industry is 26.2%. Wohlers Associat...

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Second Quarter GDP Forecast Points to 2.9% Increase

-1 DAYS AGO

The Atlanta Federal Reserve’s GDPNow model forecast for real GDP growth in the second quarter of 2016 is 2.9% on May 26, up from 2.5% on May 17. The forecast for second-quarter real gross private domestic investment growth increased from -0.3% to 0.4% following this morning's durable manufacturi...

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WCC and LCC Casting in ASME B16.34

materials_q_and_a_graphicQ: Why do WCC and LCC castings have different maximum allowable temperatures in ASME B16.34?

A: This is a very good question and a commonly discussed topic among materials engineers. Unfortunately, the answer isn't black and white-in fact, the "whys" are not very clear at all. What is clear is that the maximum allowable temperature values in B16.34 can be traced back to Section II Part D of the ASME Boiler and Pressure Vessel (B&PV) Code. However, that code contains no background information or notes to explain why those particular temperature limits were assigned. Because of this, much speculation among materials engineers exists- following along these lines:

The standard carbon steel materials (i.e., those not impact-tested for low-temperature applications, such as A216/SA216 WCC) are most commonly heat treated by normalizing, sometimes followed by tempering. Normalized steels are relatively resistant to microstructural changes at elevated temperatures. Short excursions to temperatures below the lower critical temperature (727° C /1340° F) have little or no detrimental effect on the mechanical properties of the steel. Long-term exposure at temperatures exceeding 425° C / 800° F, however, can cause graphitization, in which the carbide phase transforms to graphite causing loss of strength and toughness. WCC is actually allowed at temperatures up to 538° C / 1000° F, but B16.34 notes (as a borrowed reference from the B&PV Code) that "Upon prolonged exposure to temperatures above 455° C / 900° F, the carbide phase of steel may be converted to graphite. This means it may be permissible, but not recommended for prolonged use above 425° C / 800° F."

On the other hand, low-temperature carbon steel materials (i.e., those that are impact-tested for low-temperature applications, such as A352/SA352 LCC) are usually quenched and tempered, because they are generally tougher than normalized microstructures at the same strength level. When exposed to elevated temperatures, quenched and tempered steels are more susceptible than normalized steels to permanent reduction in strength. This is especially true when exposure temperature begins to approach tempering temperature used when the parts were produced. In addition to losing strength, tempered steels also may experience reduced impact toughness after being exposed to long-term elevated temperatures. General belief is that this is the reason for LCC's reduced maximum allowable temperature limit of 345°C / 650°F in B16.34.

Inconsistencies
Here's where inconsistencies start, however, because:

  • A216 / SA216 allows WCC to be supplied in the quenched and tempered condition if the purchaser v invokes Supplementary Requirement S15. A216 / SA216 does not explicitly require any special marking for quenching and tempering. (Interestingly, though, Supplementary Requirement S15 in A703/SA703, the "general requirements" specification referenced by A216 / SA216, stipulates a "QT" mark when the material is quenched and tempered). B16.34 (and the B&PV Code) do not place any special temperature limits on WCC when it is quenched and tempered.
  • In addition, impact tests are also allowed on a WCC casting at -46°C/-50°F to qualify it for low temperature service. This would then be a full-fledged WCC casting qualified for use down to -46°C/-50°F and minus the explicit 345°C/650°F maximum allowable temperature limit for LCC.
  • Furthermore, the B16.34 maximum allowable temperature for A350/SA350 LF2 forgings is 538°C/1000°F (with the same warning note about graphitization -not to use it above 425°C / 800°F). These forgings are also often quenched and tempered so they are essentially the nearest forged equivalent to LCC castings. If the metallurgical instability issues are the reason for the 345°C / 650°F maximum allowable temperature limit on LCC castings then, it would seem that LF2 forgings should also be limited to 345°C / 650°F.

Drawing Conclusions
Based on the above information, the following conclusions might be drawn:

  • If the reduced maximum allowable temperature for impact-qualified materials (such as LCC) are limited based on loss of toughness after long-term exposure to elevated temperatures, it would seem logical that additional, more consistent controls should be placed on all low-temperature materials (including LF2 forgings). These controls would need to extend to grades traditionally not impact tested, but that might be impact tested to qualify them for low temperature applications (such as an impact-tested WCC). In other words, maximum allowable temperature limit should be based on minimum allowable temperature.
  • If the reduced maximum allowable temperature is limited based on loss of strength from reduced elevated-temperature stability of quenched and tempered steels, it would make sense to list maximum allowable temperature limits for carbon steels as a function of both material grade and also heat treat condition. It would also make sense that quenched and tempered materials be marked in this case as well.
  • If both these concerns are driving the reduced maximum allowable temperature limits, then it would seem that the maximum temperature limits of all carbon steels should be based on both the minimum allowable temperature and the heat treat condition. In any event, it's clear that the ASME codes and standards currently contain a number of inconsistencies regarding lower temperature limits in carbon steels.

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