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  1. 506818

    Multiple PID Loops (PLC)

    Yes it's flow rate for each line that's being controlled and there will be a flow meter for each valve to PID control. I want to understand how the multiple loops will interact and what the best practice would be via the PLC code.
  2. 506818

    Multiple PID Loops (PLC)

    I have an air flow into a system which is mixed with a separate gas. Each the air and gas has its own control valve. Once mixed, the flow then goes to 10 individual lines running in parallel each line has its own control valve to adjust flow down each line. There is then an excess line where...
  3. 506818

    Spring constant for gaskets (gasket creep)

    3DDave: Did not know about the significant variation in Bellevilles. In this case, the quantities are too large to measure each one. They will be supported on flat metal washers, but the base flange is PVC. So that won't transfer the loads as much as metal flanges will, but should be sufficient...
  4. 506818

    Spring constant for gaskets (gasket creep)

    Thinking about this further, if springs are in series, would the deflection of the gasket be the same regardless of the Belleville washer and vice versa if the same load is applied? Therefore, if the torque>gasket torque required AND deflection of Belleville>gasket creep, it should work as...
  5. 506818

    Spring constant for gaskets (gasket creep)

    I'm using Belleville washers with PTFE gaskets to account for gasket creep and handle vibrations on flanges. I want to work out torque values to use. The idea is that the Belleville washers will deflect enough to account for the gasket creep in the PTFE. I'm seeing this as springs in series and...
  6. 506818

    Heat Transfer Across a Solid From Two Flowing Pipes

    TiCl4 - That's very clear, thank you. I've split the pipe into a number of sections and have a ballpark figure now. I can vary the inputs into my Excel calculator and get an idea of best and/or worst case. IRstuff - I believe what you're suggesting is what TiCl4 has eluded to, and what I...
  7. 506818

    Heat Transfer Across a Solid From Two Flowing Pipes

    Thank you for the references - I now have a copy of the book. Excuse my ignorance here. No trouble in calculating convective heat transfer coefficients (h, W/m²K). But how do I then relate this to conductive heat transfer? Is this a case of combined convection and conduction? Perhaps there is...
  8. 506818

    Heat Transfer Across a Solid From Two Flowing Pipes

    Understand CFD is the route to go. I'll see if I can get hold of the resources and update in due course. In the meantime, it would be much appreciated if someone could direct me to perhaps a similar relevant example or set of equations. I've made some convection calcs based on assuming a...
  9. 506818

    Heat Transfer Across a Solid From Two Flowing Pipes

    ...for both flows using Re, Nu, Pr numbers, etc. However, as this appears to be 2x convection + conduction, unsure on what the dT to plug into the Q=h*A*dT equation should be. My thoughts are that: convective heat on the hot side to the aluminum = conduction in aluminum = convective heat to cold...
  10. 506818

    GD& T Tolerance interpretation

    From experience, unless you have any reason to, it's always best to note tolerances apply after finishing and to use one supplier to sub-contract the plating. Even better, explicitly state on order that you require a certain plating thickness to be considered during manufacture. Most will often...
  11. 506818

    Can Finish mark be defined for a long profile using reference letters and between symbol.

    I don't see why not. However, it's best to have a defined area as it can be unclear where 'A' or 'B' starts assuming an uninterrupted profile.
  12. 506818

    Please advice on this o-ring seal design

    If it's a standard o-ring size, just follow the Parker or other standard groove designs. You'll typically make the groove OD the same as the o-ring's OD anyway. Then the groove width is standard based on o-ring section.
  13. 506818

    Thread design help

    Are you looking to seal on the threads only, or will you be using an o-ring of some kind? O-ring will be a standard groove (see Parker handbook or ISO 3601). Sealing on the threads requires an NPT (i.e. tapered thread). Have a look at Swagelok pressure ratings for tapered fittings as they give...
  14. 506818

    Please advice on this o-ring seal design

    You'll be fine. Ensure you lubricate correctly. Silicone grease will be fine with compressed air unless you're concerned about contamination. If that's a coarse M8, it's probably about one full turn of the nut so little friction once lubricated. The mating face should be machined to a decent...
  15. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    OK - so I was thinking a little outside the box. How about something that wasn't exposed to the outside, but sat inside the box? So as the internal pressure increased, the bellows inside would shrink due to the walls of the box being stiffer than the walls of the bellows? With the pressure...
  16. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    Just curious, is there anything off-the-shelf that could be used for this? Guessing you would need to pre-set the internal bellows pressure (could just be ambient).
  17. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    Great suggestion! Tbf, I have some internal volume to play with - this could be something that's retrofitted to the assembly if it becomes an issue. Tube + piston + spring won't be too difficult or expensive to create. Tell me about it... What you describe about the accumulation of water is...
  18. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    Just want to say thank you for all your input - this is great discussion! Should've mentioned from the start (didn't want to deviate from the direct problem), but here is the case: https://www.nanuk.com/nanuk-918.php?lang=lang-en I think you've all convinced me that more screws is the way to go...
  19. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    There is space to add more, just wanted the limit cost and assembly (also disassembly) time if not required. If I can ensure the plastic doesn't shear/strip, then I will be happy. I can only find sealing screws in the form of stainless steel.We have plenty of torque screwdrivers to assemble...
  20. 506818

    Screw Pull-Out Force in Polypropylene - Calculation

    Thanks all - I'll try to cover the responses. Also added an image to show the problem in question. [You calculations are based on the force needed to hold your lid on. You want to grossly exceed this, and torque the screw down to its proof load. I am checking your numbers using my own...

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