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  • Users: thermmech
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  1. thermmech

    Steam tracing effectiveness on 40" acid gas line

    Greetings! A 40" LP acid gas line (normally no flow) with 130 degC temperature is LP steam traced. Steam 4.1 barg (140 degC) is used to keep the pipe wall at 130 degC. Internal corrosion occurred die to water condensation. Two questions: 1. During no flow condition, should the steam tracing...
  2. thermmech

    When vessel MDMT on nameplate needs to be changed?

    I am carrying out API 579 brittle fracture assessment for CS knockout drum (KOD): MAWP = 14.5 barg MDMT = -16 degC New low oper. temp = -27 deg C @ 10 barg. Thus, CET = -27 degC. As per assessment calculated MAT = -30 degC < CET [OK] Basis for MAT reduction is PWHT done post-fab...
  3. thermmech

    Selflocking of spring hangers

    In our plant we had number of cases where spring hanger locking nuts have moved into "locked position" due to piping vibration - nuts tend to slide down. That resulted in spring hanger casing damages and temporarily increased piping loads. To minimize such occurrences I'm thinking we could...
  4. thermmech

    Plate and frame exchanger size increase , NBIC R stamp requirement

    We are revamping an LNG train and some plate and frame amine exchangers need to have some 10% extra plates added to handle additional heat duty. Question has been asked whether this constitutes alteration and requires R stamp. We are in Middle East and there is no change to the size of the...
  5. thermmech

    Strainer design philosophy re acoustic vibrations

    I already asked this question in thread384-356365 (apologies for cross-posting), however, no-one replied re strainer design criteria with respect to acoustic phenomena. I'm kinda hoping I'm going to have more luck here. :)
  6. thermmech

    Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy

    We are experiencing a vibration / noise in a stretch of 38" piping downstream from compressor to the first heat exchanger. In this stretch of piping there is a conical strainer with fine mesh. Recently we have removed the fine mesh from the strainer perforated plate (basket). There was no noise...
  7. thermmech

    Finding a leak location - underground 4in utility line

    Our 4" utility line has a bad leak. Fluid: water Pressure: 5 barg Temperature: ambient (above 0 deg) Pipe lenght: 800 m Depth: 1 m, covered with 30 cm of concrete The leak is quite bad indicating construction issue, and not corrosion. I am trying to understand capabilities of various...
  8. thermmech

    PWHT of CS Channel with 316L SS Cladding or Weld-Overlay

    We have a CS tube exchanger (both SS and TS) where CS tubes have corroded. TEMA type: CKU (channel butt-welded to tubesheet, originally PWHT for Code reasons, not service) Shell side: hydrocarbons boiling (corrosive agents) Tube side: high pressure saturated steam Channel = SA-516-70N, thks =...
  9. thermmech

    In-Situ L:ocal PWHT of Column

    We want to repair by a weld build-up a 2 meter bend of a column that has suffered a loss of wall due to corrosion. The bend is in the lower third of the column. Column info: SA-516-65N OD = 3m L = 22 m column is supporting another vessel above design pressure is low, ext pressure is governing...
  10. thermmech

    Crack Propagation if no load

    Hello there, I apologize in advance if I am asking a question that has been answered elsewhere on the forum or is really easy to get the answer to - I am not a materials engineer and need some guidance. We had a failure of a CS strainer bucket - strainer nom dia 32" - strainer body = forged...
  11. thermmech

    Kettle Reboiler Vapor Space Calcs

    Greetings! We have a C3/Mixed Refrigerant Evaporator (kettle reboiler) level control issues, where "kettle" reboiler is: - BKM type, 1600 mm (4200 mm) x 8100 mm - not conventional kettle, bundle is stabbed into the horizontal vessel, presumably due to economy - demister pad at ~850 mm above...
  12. thermmech

    Liquid carryover and demister pad support ring design

    We are having a number of vessels with demister pads consisting of 6 or more sections (nicely fitting through the manhole), where demister pad support ring welded to the vessel ID is split into 2 pieces. The gaps in the ring are approximately 12", and are filled in with removable ring pieces...
  13. thermmech

    38&quot; triple-offset butterfly valve passing - URGENT

    Greetings! We need urgent help :) 6 pcs of 38" triple-offset butterfly valves are passing (more than 50% of number installed). The valves worked fine for about 12 months. Increasing the torque from 75% to 100% didn't help. Service: isolation valves for mercury removal filters (dry natural...
  14. thermmech

    U-Stamping / Documentation for &quot;Replacement-in-Kind&quot;

    I am now outside of North America and am trying to sort out PV safety / integrity policies within my new company which is an owner-operator. We are replacing lots of S&T bundles which were mostly designed and fabricated in the mid '90s. Local fabricators are coming back to us asking whether...
  15. thermmech

    DEU S&amp;T HEx: Reason for Leakage at Girth Flange

    I need help with troubleshooting leakage on 22 x 240 "DEU" TEMA heat exchanger.The service is "Anti-Hydrate Heater", it is using saturated steam at 300# to preheat inlet natural gas from 15C to 30C during the winter. Location is Middle East. Material of construction is CS. The high pressure...
  16. thermmech

    Stress Ratio for Calculation of Hydrotest Pressure

    As per UG-99, hydrostatic pressure is = 1.3 x MAWP X (Sall @ Tamb / Sall @ DT). I have been presented an argument that the presence of vents and drains c/w blind flanges on SS vessels limits the hydrotest stress ratio, "Sall @ Tamb / Sall @ DT" to "1.0". The vendor is stating that the...
  17. thermmech

    Consider External Loadings of Flange MAWP Rating

    Hi, In COMPRESS Nozzle Dialog "Add ASME B16.5/B16.47 Flange" there is a check box for "consider external loadings on flange MAWP rating". How does COMPRESS adjust standard flange MAWPs for external loads? Thank you!
  18. thermmech

    In-tube Velocity Limit to prevent Erosion

    Greetings! I have found some recommendations on maximum in-tube velocities for exchangers (no clarification whether straight tube or U-tube construction) in order to prevent erosion. They come from Wolverine Tube Heat Transfer Data Book. For water service and low carbon steel, the limit is 10...
  19. thermmech

    Aerial Cooler Header Box in Lethal Service

    RE: Lethal Service I went through the threads and also examined ASME VIII-1 UW-2(1)(c) - and I am still not sure whether aerial cooler header box joints can be made as Cat C (corner joints) with 100%UT or they have to be as per Figure UW-13.3.
  20. thermmech

    Once-Through HRSG Duct Burner Flame Stability

    Greetings! I am working on a project where a large horizontal OTHRSG is envisioned after a gas turbine. OTHRSG is supposed to have supplemental duct burner positioned AFTER first heat exchanger module. This is a case of so-called mid-firing. We are trying to establish whether: 1. there is a...

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