Researchers at the U.S. Energy Department's Pacific Northwest National Laboratory developed cement that can heal itself when cracks occur. Using self-healing cement for geothermal wells would save geothermal plants millions of dollars and would reduce the amount of downtime necessary for repairs.

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Cement production is responsible for more than 5% of global yearly CO2 release, university researchers say. Substituting geopolymers for cement could lead to reductions in atmospheric carbon dioxide. These materials also may be more resistant than cement to high temperatures and chemicals.

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ASME Standards often require careful reading in order to interpret them correctly and engineers can be left with questions about some details. In this post we take a look at an engineer’s welding question related to a vessel’s heat treatment.

Question: My shop is constructing a Section VIII Division 1 vessel that uses SA-516 Grade 70 Normalized Plate Material. The Vessel is not exempted from Impact Testing. Can I use an existing PQR qualified with SA-516 Grade 70 as rolled plate to support the WPS I want to prepare to weld on this vessel?

Reply: The short answer to the above question is No.

UG-84(h)(2)(-b) says “be in the same heat treated condition” as one of the requirements to be fulfilled for the test plate material used to qualify the PQR with impact testing. Therefore a PQR qualified with SA-516 Grade 70 as rolled plate cannot support a WPS written to weld SA- 516 Grade 70 Normalized Plate Material.

Someone could potentially misinterpret the phrase mentioned above in quotes to be the post weld heat treatment (PWHT) instead of the heat treatment condition of the base material.

Note that Section IX does not list the base metal heat treatment condition as a supplementary essential variable. So this is a perfect example of a construction code invoking a supplementary essential variable in addition to the ones provided in Section IX.

Another subtle point to be noted here is that a PQR qualified in accordance with Section IX rules doesn’t need to show the base metal heat treatment condition in the PQR since it is not a supplementary essential variable in Section IX. However, in order to make the same PQR compliant with Section VIII Division 1 impact testing rules, base metal heat treatment condition needs to be recorded in the PQR either explicitly or by attaching a material test report of the test plate material used to qualify the PQR.

In summary, the absence of verifiable evidence about the base metal heat treatment condition can make the acceptability of an existing PQR meeting Section IX requirements questionable for Section VIII applications.

Editor's Note: This is a sponsored blog post by HSB Global Standards.

Have you ever wondered why certain standards have changed? It’s an engineer’s responsibility to research and follow the latest standards, but understanding why they have changed can be helpful when bringing these revisions back to the workplace. This week we take a look at an engineer’s question about a change to ASME Section VIII pressure test rules.

Question: While reviewing Section VIII, Division 1 pressure test rules, I see that painting or coating pressure retaining welds in a vessel prior to the pressure test is now prohibited. When was this change made, and why?

Reply: Several years ago, tests were conducted to assess the pressure containing capability of different paint systems when subjected to a hydrotest. The test results clearly show the ability of paint to mask leak sources in the pressure containment. On the basis of published test results as well as recommendations from organizations that operate and maintain pressure equipment, Section VIII approved revisions to both Division 1 [UG-99(k) (hydrostatic test) and UG-100(e) (pneumatic test) ] and Division 2 [8.1.2(e)] that will require that vessel pressure-retaining welds not be painted or otherwise coated either internally or externally prior to the pressure test unless permitted by the user or his designated agent.

When painting or coating prior to the pressure test is permitted, or when internal linings are to be applied, the pressure retaining weld shall first be leak tested in accordance with ASME Section V, Article 10. This test may be waived with the approval of the user or his designated agent. The original provision prohibiting painting or otherwise coating or lining a vessel either internally or externally prior to the pressure test for vessels in lethal service remains.

Note that the user also has responsibility to declare whether or not a vessel should be constructed for lethal service, where the term “lethal” is defined in Endnote 65 of Section VIII, Division 1. Also note that Section VIII, Division 2 does not define lethal service, and therefore the user and/or his designated agent have full responsibility to decide whether or not it is acceptable to paint or code pressure retaining welds prior to the pressure test, which should be defined in the Uses Design Specification (UDS).

Editor's Note: This is a sponsored blog post by HSB Global Standards.

I'm in the midst of a winter repair project that has me seeking the best of the best duct tape, within reason.

The repair stems from a Labor Day river tubing trip down the Battenkill in nearby Vermont. (Photo at right is not me.) I own six Intex River Run 1 inflatable tubes that friends and family use several times a season. The last time they were used, one of the tubes emerged from the river with a 10-inch jagged gash. It had to have happened within the last few minutes of the 5-hour float, as the occupant waded ashore just as the tube became useless. This is the first popped tube in a dozen trips.

It might be good enough to throw it out, and suffice with a fleet of five tubes or just buy a new one for about $20. But this will likely happen again, so it makes sense to invest in repair materials that will cost about the same. Besides, one less tube is one less person or ice chest of beer that gets to float the river. Even in the cold of January I'm thinking of warm days ahead.

The tubes are manufactured from 8 gauge vinyl sheeting. Intex makes a repair kit that comes with a small amount vinyl patch and vinyl cement, but the patch was too small for my use. I instead ordered a patch for a vinyl airbed, and it was large enough for me to trim and cover the gash. After applying the adhesive I clamped the tube between two small boards and left it to sit for 72 hours in the basement.

After that I blew the tube up indoors and put 20 lb. of dumbbells on it; 24 hours later there was no air leak. The patch job seems stable and it will likely hold up. Not bad considering I spent about $7 so far on materials, though I've waited two weeks for the deliveries.

I am a bit worried about it the patch's integrity for a full day of tubing however. Ideally this patch will support a 200-lb. load for 5 hours, while being constantly exposed to water and UV light. There's also the chance for more abrasion from rocks and other river debris at the patch site. If this patch were to fail mid-float, someone is walking the rest of the way to the car.

Naturally I'm investigating the best duct tape possible for this function. I'm currently leaning towards Mil Spec duct tape, as known as 100 MPH tape. I'd heard of it before and the reviews seem positive. While researching it however, I learned of AMG MG260 Military Grade duct tape, but I can't distinguish what makes it difference that 100 mph tape (other than 100+ mph wind resistance?), or a tape like Sticky Ass Tape, which also claims to stick even in the face of 200 mph wind. Popular Mechanics backs Gorilla tape for water resistance tasks.

I've searched the CR4 archives and there was never a "best tape" debate. If you have an opinion, weigh in. I've only got five months to figure this out.