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  1. moltenmetal

    Thermal Inductors- Heat Flowing from Cold to Hot Without External Energy Input?

    https://advances.sciencemag.org/content/5/4/eaat9953 Discuss... How can you generate, with no energy input, an unnatural temperature difference? Given that a temperature difference, however it has been established, can be used to power a conventional heat engine, how does this NOT violate the...
  2. moltenmetal

    Carbon Capture and Storage (CCS): options real and imagined

    I suggest a thread where the technical and environmental aspects of various options for carbon capture and storage will be discussed. Participants in this thread assume, for the purposes of the discussion, that fossil CO2 emissions to the atmosphere are undesirable and that it is a desirable...
  3. moltenmetal

    I've discovered overunity! Not really...

    Hi roundtable-type people- Paul Martin here, who still likes to keep his real name private like a superhero on Eng-Tips...but today I need to trust you enough to reveal my Clark Kent identity- hopefully for your amusement! I've had an unexpected and very welcome slow period at work, which has...
  4. moltenmetal

    Girls in STEM is failing both girls and STEM?

    https://www.thestar.com/opinion/commentary/2017/03/23/girls-in-stem-culture-is-failing-both-girls-and-stem.html Read the article, THEN discuss...
  5. moltenmetal

    A Waste of Talent: Engineering Under-Employment in Canada

    The Ontario Society of Professional Engineers has (finally) released a new report, giving evidence of the massive under-employment of engineering grads and immigrants here in Canada. http://c.ymcdn.com/sites/www.ospe.on.ca/resource/resmgr/DOC_advocacy/2015_REPORT_Underemployment_.pdf Per the...
  6. moltenmetal

    Experience with metal-filled Teflon seats

    Hi All- just wondering if anyone has documented experience, good bad or ugly, with ordinary (i.e. not trunnion type) 3-piece ball valves using 50% stainless steel or nickel powder-filled Teflon at temperatures above the normal upper service limit of reinforced Teflon, which I would put at around...
  7. moltenmetal

    Transformer standby losses

    Hi All: thanks in advance for your help. We have a light manufacturing facility which seems to draw quite a bit of power when nobody is in it...and yes, we've looked for hidden grow-ops and haven't found any! Peak draw during peak production is on the order of around 220 kW, plus more in...
  8. moltenmetal

    Pump for liquid sodium

    We have an application for low pressure liquid sodium circulation. Temperature is only about 10 C above melting (ie around 110 C)- this is not a high temperature heat transfer application. Electromagnetic pumps are apparently often used but we have a fairly low flow (a few USGPM) and aren't at...
  9. moltenmetal

    Noalox for copper to aluminum wire joints

    Apparently this material is zinc powder in a polymer grease binder which is commonly used in copper to aluminum wire joints. Apparently the idea is to put a film of the compound on the aluminum part, then wire brush the part or wire to remove the aluminum oxide, leaving the grease to prevent...
  10. moltenmetal

    Sizing Needle-type control valves in laminar and transitional flow

    In case this topic interests you, here's a reference to an excellent paper on the subject. Regrettably it's in AIChE's Chemical Engineering Progress, so it's not public content- but if you use needle-type globe valves as control valves or manual flow regulation valves for liquids, you'll want a...
  11. moltenmetal

    Minimum tube diameter for refractory-lined tubesheet

    I'm wondering if there is a minimum tube diameter recommended for heat recovery steam generators which are using gas hot enough to require a refractory-lined tubesheet. My concern is a practical one related to how much refractory material you need between tubes (i.e. relating to both tube...
  12. moltenmetal

    Material for Steam Generator Instrumentation

    Hi All, I have a post over on the Boilers and Pressure Vessels forum on this topic which is not getting me the advice I need. It's very much a materials/corrosion question as well as a question of what people typically use, or more properly, now strictly they avoid austenitics in this service...
  13. moltenmetal

    Steam Generator Instrumentation

    We have a small non-fired (electric) high pressure (2000 psig operating) continuous process steam generator in our scope on a particular project. The vessel will be ASME VIII-1 and the steam piping will be to B31.3. Both are carbon steels or low alloys. The steam generator feed will be boiler...
  14. moltenmetal

    Fraudulent Mill Certs

    We received from a large, reputable distributor, four lengths of Chinese-origin 316/L pipe. All four had the same heat number and other mill markings. Mill cert list compositions in accordance with the spec and also indicate "100% PMI". On-site PMI testing with an XRF gun (later confirmed by...
  15. moltenmetal

    How thick a tubesheet?

    When using large (2" NPS sch40S pipe) tubes in an exchanger, how thick does a tubesheet need to be to ensure a reasonable chance of sealing by roller expansion alone? Materials are 800HT for both tubes and tubesheet (i.e. it's a HOT service). Service pressure is ~12 psig which is also ~ the...
  16. moltenmetal

    Inhibitors for Citric Acid descaling solution

    What sort of inhibitor is used in citric acid descaling solutions? I've seen commercial inhibitor brand names mentioned but want to understand what class of chemicals these are and how they work to inhibit parent metal corrosion.
  17. moltenmetal

    control valve sizing for extremely low flows

    Does anyone have good, proven sizing equations for extremely small control valves (Cv less than, say, 0.01) for liquid services, where the flow through the trim (much less the body!) is clearly laminar? Unless I've missed something, the typical low flow control valve manufacturers (Kammer...
  18. moltenmetal

    Broken Drill Bit in Inconel Tube

    We've got a small piece of high speed steel drill bit twisted off inside an Inconel 600 thermowell (a horizontally oriented blind hole about 1/4" diameter and 8" deep, with the drill bit between about 4" and 4.5" from the open end). The geometry, location and size of the well and bit etc. are...
  19. moltenmetal

    Tantalum and galvanic corrosion

    Where is tantalum in the galvanic series? Is it significantly less noble than graphite? From what I've read, tantalum suffers from severe hydrogen embrittlement from pick-up of nascent hydrogen in aqueous services when in a galvanic couple with other metals, and hence needs to be electrically...
  20. moltenmetal

    Examination for Ti Embrittlement

    We're working with a small used Ti gr7 pressure vessel. The surface shows extensive, blue-coloured heat stain from the use of external band heaters. The concern is nitrogen/oxygen embrittlement from long-term use with titanium temperatures beyond the ASME code limit of 315 C for the material...

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