Materials In High Temperatures

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In some applications, such as underground piping, temperatures within the range from 90 °C to 150 °C may be considered high temperature. The focus of this article is significantly higher temperatures, primarily above 650 °C.

Ordinary iron-carbon alloys, including carbon steels, have been used successfully from room temperature up to temperatures of about 480 °C, and for short periods of time up to 590 °C. At temperatures beyond this, ordinary steels tend to corrode rather heavily, and the formation of surface oxide scales is ineffective at reducing these rates. However, it is possible to resort to cementation (surface-diffusion treatments) on carbon and low-alloy steels to render them more resistant to corrosion. Depending upon the corrosiveness of the medium involved and the exposure temperature, one or several of the following may be used: siliconizing, aluminizing, chromizing, or a somewhat different method of surface treatment such as plating, plasma spraying, cladding, and so forth.

The most common alloys used for exposure at high temperatures are the iron/nickel/chromium alloys, often referred to as stainless steels (SS). The materials used may be cast or wrought. For most furnace operations, the cast metals are used.

If medium- or high-alloy steels are used, chromium-bearing SS are generally recommended. Both the straight chromium steels (400 series) and the chromium/nickel/steels (300 series) are used successfully up to approximately 870 °C. At still higher temperatures, the higher nickel and higher chromium alloys of the 300 and 400 series are used, and at temperatures in excess of 1,100 °C, only the alloys with more than 20% Cr can be used with relative safety, particularly for short or intermediate periods of time.

During long-term use at high temperatures, a phenomenon known as creep is experienced, during which relatively low stress may cause a metal to deform very slowly and possibly rupture. The percent elongation of a metal component is called strain, and the strain per unit time – typically not a constant at high temperatures – is called creep. Although this is not a corrosion phenomenon, it is nevertheless a factor that must be understood by anyone considering or recommending alloys for use at very high temperatures. It is on the basis of the creep to be expected at the operating temperature that furnace parts are designed to withstand the mechanical stress.

At still high temperatures, it may be necessary to use refractory metals that have good high temperature mechanical properties, plus melting temperatures greater than 1,650 °C, as shown in Table 1. Alloys of chromium, niobium, molybdenum, tantalum, rhenium, or tungsten will therefore be considered. Although titanium and zirconium melt above 1,650 °C, their high temperature mechanical properties are rather unsatisfactory, so they are not generally considered in the category of refractory metals. Although pure vanadium melts near 1,900 °C, the low melting point of its oxide makes it a poor choice for high temperature applications. While alloying with metals that melt at higher temperatures will generally produce a higher-melting material, the resulting properties and high-temperature performance of specific candidate alloys must be fully understood.

Metal ° C ° F
Aluminum 659 1,218
Beryllium 1,280 2,340
Carbon 3,600 6,512
Chromium 1,890 3,430
Cobalt 1,495 2,723
Copper 1,083 1,081
Gold 1,063 1,945
Iridium 2,454 4,449
Iron 1,539 2,082
Lead 327 621
Magnesium 650 1,202
Manganese 1,245 2,273
Molybdenum 2,625 4,760
Nickel 1,455 2,651
Niobium 2,468 4,475
Osmium 2,700 4,892
Platinum 1,773 3,224
Rhenium 3,180 5,756
Rhodium 1,966 3,571
Silicon 1,430 2,605
Silver 961 1,761
Tantalum 2,996 5,425
Tin 232 450
Titanium 1,668 3,034
Tungsten 3,000 5,432
Vanadium 1,900 3,452
Zinc 419 787

This article is adapted by  Norm Moriber from Corrosion Basics–An Introduction, Second Edition, Pierre  R. Roberge, ed. (Houston, TX: NACE International, 2006), p. 218-219

Content reprinted with permission from Materials Performance Magazine.

Inline Inspection Electronics Lab Expansion

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Mears Integrity Solutions is proud to announce the expansion of its West Road Inline Inspection Electronics lab in Houston. Rick Jacob, Mears’ manager of the lab, and of engineering services explains further.

Q: WHAT IS THE IMPORTANCE OF A MEARS ENGINEERING LAB TO SUPPORT THE INLINE INSPECTION OPERATION IN HOUSTON?

All operations for the Inline Inspection division are run out of our Houston facilities. That’s where our inspection tools are prepared for specific inspection runs prior to mobilization to the job site and are refurbished after the runs are complete. The Engineering Lab in Houston provides three functions in support of these operations:

  • provide detailed technical engineering support to operations;
  • provide repair facilities in the event of an electrical or mechanical failure of a tool; and
  • provide the facilities to successfully perform a root cause analysis in the event of a failure during an inspection run.

Q: CAN YOU EXPLAIN WHAT THE PROCESS IN THE EVENT WE HAVE A FAILURE DURING AN INSPECTION?

A failure during an inspection run is considered a very serious event and is a top priority for the division. Considerable effort goes into preparing each tool for an inspection run. The tool is then set up to record data collected during the run, loaded into the launcher, and launched into the pipeline, typically being driven ahead of the product running through the line. At the end of the run, the inspection tool is received in a trap and removed so the data can be downloaded for analysis.

Many things can go wrong when a sophisticated mechanical and electrical device is put into a pipeline and driven substantial distances through all the pipeline features, such as bends, tees, and valves. The tools are subjected to substantial pressure and driven at high velocities. In most cases the tools perform the inspection without problems and provide our analysts with good information; however, even after careful preparation, things sometimes go wrong and cause failures.

Procedures are in place to respond to a failure during a run. Once the possibility of a failure is recognized, an Inspection Failure Investigation, or IFI, is immediately implemented. The goal of the IFI is to collect as much forensic information as possible relating to the failure, analyze that information, and determine the root cause of the failure. Once the root cause is determined, it is used to establish short or long term solutions, or both, so that the lessons learned can be implemented to minimize the chances of the failure occurring again.

The Electronics Lab is an important part of that process. The lab provides the facilities to review the data, dismantle and inspect relevant parts of the tool, measure the electronic signals being generated within the tool, and perform advanced troubleshooting and other testing on the tool to determine the cause of the failure.   Once the cause of the failure is found and repairs or other solutions are put into place, the lab provides the test facilities to verify that the problem is resolved.

Q: WHAT VALUE DOES THIS BRING TO THE CLIENT?

Obviously, successful pipeline inspections are very important to our clients. Substantial man-power is devoted and expense incurred to inspect a pipeline. Every effort must be made to ensure our clients that we can successfully inspect their pipeline and do so while minimizing that man-power and expense. We use a First Run Success (FRS) metric to measure our ability to achieve these objectives.   A high FRS rate indicates a high probability of successful pipeline inspection with a single run without the need to repeat an inspection due to a failure. Our goal is to maintain a high FRS rate for our customers. While efforts are focused on performing successful inspections with a single run, occasional failures are unavoidable. Mears has invested substantial funds to provide the facilities and man-power so our engineering team can analyze forensic information relating to a failure and develop real solutions to mitigate the possibility that a failure will recur. This constantly improves our FRS rate and provides better service to our clients. We are constantly working to improve the design of our tools and our inspection procedures.

By using the facilities of our Electronics Lab, we can ensure our clients that we can develop real solutions to real-world issues relating to our inspection tools, procedures, and processes. This constant quest to improve the quality of our services ultimately provides value to our clients by maximizing the all-important FRS rate.

Q: TELL US MORE ABOUT THE FUTURE…

Current plans for 2015 include investing in additional staff to support the Electronics Lab in Houston. We will be hiring two additional engineers to work out of the Houston facilities as well as an Electronics Technician to work exclusively in the lab.

We have planned for a major expansion of the lab this year and look forward to enhancing the resources available to us to further improve supporting our clients and the Operations Department here at Mears Inline Inspection.

AC Mitigation – Out of the Box Thinking


An AC Mitigation bid opportunity  brought out the best of Mears’ innovative, “Out of the Box” thinking. The project required the installation of an AC Mitigation System near Sacramento, CA. The design and specifications were provided by the client. The installation called for bare copper cable to be installed in a horizontal column of Conducrete®, a conductive concrete that is often incorporated into Cathodic Protection and AC Mitigation designs where low-impedance grounding is required.

The challenge Mears faced was how to effectively install the Conducrete material to the design specifications, which were complicated by the narrow Right-of-Way, and called for the type of innovative thinking for which Mears is known. From the start of the bidding process it was evident that traditional trenching of the cable and installing the Conducrete in the open trench would not be feasible. The copper cable was required to be centered in a column of Conducrete with specific dimensions. Adherence to these specifications would be verified by both third-party and customer inspectors on site throughout the entire project.

The concept for achieving the AC Mitigation project objectives was loosely adapted from Mears’ patent pending proprietary technique for installing a conductive cable-type linear anode centered in a horizontal column of coke breeze. That process has been used successfully for hundreds of miles of linear anodes throughout the United States. The solution Mears developed for this project involved design and fabrication of a custom piece of equipment for placing the cable and Conducrete as specified. This piece of custom equipment was towed behind the trenching machine, allowing for the copper cable and Conducrete to be installed in a single pass.   If the copper cable and Conducrete were not installed at the same time it would have been difficult to prevent the trench from caving in and nearly impossible to maintain the cable’s centered position during a second pass.

The development of this specialized equipment allowed for a high level of production, and the project was completed on time and on budget.   The successful completion of the work in 2013 led to the opportunity for Mears to perform the second phase of the AC Mitigation project; again the project was completed on time and on budget.

Though the equipment was developed for placing Conducrete, it can be adjusted to handle different types of engineered materials that may be called for in other designs.

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