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  1. Doug Hunter

    PTFE seal hardness testing

    You can try ASTM D 1710, ASTM D 882 or ASTM D 4745 to see if they offer any useful information. Do you know if the PTFE has any glass fill? I don't recall any hardness checks or requirements in the PTFE seals I've worked with.
  2. Doug Hunter

    Pump shaft sheared

    I agree with Tugboat that the failure surface has rubbed away all the clues. Does the left section of the shaft have an eccentric potion on its right end?
  3. Doug Hunter

    Closed Loop Piping-Vacuum Issue

    Good morning. The answers to your latest questions about air depends somewhat on the details and air robustness of the heat exchanger, but generally I don't think that you need to purge every time. What I can tell you with certainty is that as long as the gear pump suction line at the sump...
  4. Doug Hunter

    Closed Loop Piping-Vacuum Issue

    Good morning. You'll have to consider the effect of air on the performance of the heat exchanger and the bearing, but in my experience the pump and the entire system will tolerate the presence of some air. High pump speed and high discharge pressure can create an increased risk of cavitation...
  5. Doug Hunter

    Practical Implications of Impact Testing

    Sorry, I don't have access to Table or Figure 323.2.2-1, so I can't comment.
  6. Doug Hunter

    Practical Implications of Impact Testing

    When you buy the material it should be certified by the supplier to meet the requirements for impact strength as well as all its other rated properties. I think that the toughness of standard materials of construction is already known as a function of temperature. You just need to find the...
  7. Doug Hunter

    Dry Co2 95% sizing Orifice meter

    Thanks, LittleInch. I agree with the others that the Supplier is your best resource. Per the reference provided, it looks like they use a standard round orifice plate. If you still want to do some calculations yourself, here's the standard orifice equation I've always used: dP [kPa] =...
  8. Doug Hunter

    Dry Co2 95% sizing Orifice meter

    Can you please elaborate on the meaning of a "Senior orifice meter"?
  9. Doug Hunter

    Multple single segment position

    The top 0.08 controls the left-to-right position of the slot to the 10.0 hole (A). The bottom 0.05 essentially controls the perpendicularity of the slot walls to the 9.4 hole (B). In my opinion, both have meaning. The position is allowed to vary more than the perpendicularity, and the top row...
  10. Doug Hunter

    Connection Between Tanks

    You need to kindly provide more details regarding the function of the tanks.
  11. Doug Hunter

    Closed Loop Piping-Vacuum Issue

    To answer your question directly, I don't think that the vacuum would cause a problem in the gear pump start up, unless it caused a start-up torque that exceeded your motor capability (unlikely). However, I'd also like to elaborate on your premise: unless your gear pump has some unusual sealing...
  12. Doug Hunter

    Jacking Oil Pump Air Lock Bleed Valve

    I agree with Snickster that you need to work out your math. If there is low enough relative flow resistance in the vent line, you might suck air. I agree with LittleInch that you would be best served by understanding the source of the air as part of your problem solving process. The system...
  13. Doug Hunter

    Fan blade worn out

    Can you add a zoomed out picture?
  14. Doug Hunter

    Racing oil for historic engine

    It is safest to follow the original oil spec. Thicker (higher viscosity) oil will work as well for temperatures above freezing, and reduce wear rates, but will cost you some fuel economy and power. 4 bar is plenty of pressure at idle, or even 1500 rpm. The type of racing you are doing can...
  15. Doug Hunter

    allowable stress value in creep region for 1.0345

    I agree with RVAmeche that it is important to understand if the table values do, or do not, have the safety factor already applied. It is also important to be clear on the assumptions for the data. What is actually happening over 100k or 200k hours? Is there a cycle assumed for temperatures...
  16. Doug Hunter

    allowable stress value in creep region for 1.0345

    What is the source of your values? What is happening the the test samples for 100,000 and 200,000 hours?
  17. Doug Hunter

    Two Pumps of Different Product and Ratings Pumping into a Common Header

    I recommend that you add a hydraulic schematic to go with your verbal description.
  18. Doug Hunter

    clogged suction or discharge pump linr

    My first question is: is the pump a dynamic pump or a displacement pump? My second question is the same as LittleInch: what is the baseline to which you are comparing?
  19. Doug Hunter

    MIL-L-23699 OR MIL-L-7808 hydraulic oil

    I second Tugboat on the viscosity. Secondarily, you can compare the additive packages and what functionality they are designed to provide, and if those might be related to your failure mode.
  20. Doug Hunter

    calculation for tightening torque

    The first question I would address is whether the loading is dynamic or static, and how many stress cycles. The second is what safety factor you need for your application. A third is what kind of statistical variation in strength the bolt exhibits (this may be built into proof load). The bolt...

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