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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

16 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

16 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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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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