EDC XIII Which knife or knives are you carrying today?

Morning.

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More range time yesterday ....

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Edgeoflife said:
This particular sub assembly is fairly simple in comparison to the rest of the equipment and is solely mechanical in nature but is just as important as the rest. There are only a handful of parts but all are subjected to a harsh environment operating a few miles under ground (drilling an oil/gas well) with up to 1000 gallons per minute of abrasive mud, filled with additive chemicals flowing through and around these parts with high pressures and high temperatures (relative to the design and materials etc) so the potential to erode away everything quickly is a concern if not setup correctly. everything is scrutinized bc you don't want to be the reason the rig had to stop drilling for days which is expensive.

For this particular piece of equipment, the rubber seals on the piston in that bore need to survive long enough in the environment to get that section of the job done, say 100 hours at a time, before needing rebuilt and parts replaced, so the seal’s extrusion gaps have to be as tight as .003” diametrically or .0015” on each side in between the bore wall and piston OD. Nothing too crazy but too tight and it will bind up and too loose it will fail within hours in a multitude of ways and it will only get looser as it runs so all parts are machined and finished with only a few thou for min/max tolerances and have to be measured at several steps in the assembly process while taking into account any potential tolerance stacking to insure those spaces between the bore ID and piston OD, where those seals will live, fall within the tolerances that have been honed in over time/ experience to work. Idk how interesting that is but a pic is worth a thousand words I suppose and yes Everything in the Oil industry is definitely expensive!

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Stretch 2 XL again today
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Thanks! I figured there would have to be at least a few liquid-tight seals. Four decimal places seems like it's more common now than, maybe fifteen years ago? "Crazy" starts at about seven, IMO.

I didn't think about tolerance stacking, and while I would want to know how to do those calculations....

I would leave the paperwork to the engineers!
 
Had to take the wife to Walmart this morning and just happen to see one of the ozark trail crossbar locks figured I would give it a try. Fully expected it to be crap but it’s actually pretty darn good for $8IMG_8745.jpegIMG_1522.jpeg
 
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