2016 POTD Thread Archive

The company I worked for had air operated pumps for pressure testing well head equipment. Some of the equipment we had at the shop was rated for 10,000 psi and was tested to 20,000.
At the well site we would use water to well head pressure or in the winter glycol, to check the connections. Or on occasion nitrogen if pumping equipment wasn't available.

Greg
 
1 month ago I had a Chinese benchtop mill and lathe, nothing bad to say about them as I did lots of projects and some paying side jobs with them. But as of today i now have a combined weight of about 9000lbs of American iron in my garage. 17"(19" swing) Sidney lathe moved in. And the Kearney & treckner #2ch mill holding down the back corner. Love having the heavy machines!

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Just one more note for me on the pressure testing. And hman, you're more than welcome to anything I know about and can add to the forum. I enjoy explaining things. My sister has always accused me of going way overboard when explaining things. I'm just detail oriented I guess.

Sometimes the pressure is from the outside. In the downhole environment, it's called negative pressure. Lots of funny hydraulic stuff goes on dealing with the weight of the thousands of feet of drill pipe, collars, and associated BHA's, the balance of WoB (Weight on Bit) vs the buoyancy of the string due to the weight of the drilling fluid or completion fluids. Pressures reach upwards of 20,000 psig at times. I remember one tool we made that suffered a collapse that I never would have dreamed of. Pressure is nothing to laugh at. There are bearing housings just above the bit that are actually pressure compensated by a moveable piston in a sidewall of the housing that allows the mud pressure outside to push the piston in, equalizing the oil filled housing internal pressure. There are no seals that are capable of withstanding some of the pressures down there, so other methods must be used to deal with them. Nothing like a mud invaded bearing housing to ruin a driller's day.

So, for testing against negative pressure, of course the first thing that may come to mind is simply to pull a vacuum on the vessel under test. But remember, that's only 1 atmosphere at best, <15 psi. Hardly worth the trouble. So how? Usually, things subject to negative pressure testing aren't large, so they are put inside a high pressure test chamber. This test chamber of course has been tested in the conventional way, so after the DUT (device under test) is placed in the chamber, it is pressured up to what the DUT must pass, some percentage over expected working pressure, or in a destructive test, all the way to failure. This generally reveals engineering problems such as material selection or mechanical errors such as thin walls or badly toleranced seal areas. Naturally, this assumes manufacturing followed engineering instructions to the letter. This general statement applies to all pressure testing. Aside from collapse or leakage, another checkpoint (also applies to internal testing) is material deformation, both plastic and elastic. Not as obvious as a total collapse or rupture, but important from a materials standpoint because some of these designs will see pressures rise and fall cyclically by design, and material fatigue is a concern.

OK, I have begun to ramble again. Maybe my sister is right........
 
Replaced the cracked column on my new to me Grizzly mini mill. It went well except for the fact that some of the tapped holes on the replacement column from Grizzly were misaligned which is rather ridiculous.
Here is a photo where the misalignment of the holes is clearly noticeable.
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Randall Marx said:
Don't tell me those holes are supposed to be equally spaced from center!? :face slap:
Click to expand...

Indeed they are. Very frustrating and a bit disappointing. If I ever need any more parts I'll order from Little Machine Shop in hopes there will be a little more attention payed to the product.


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Back in the 80s, I bought a Williams & Hussey molder. Old, established US company. The molding knives bolt onto opposite sides of the square cutterhead, and are aligned by bumping them up against the bolts. Well, I had a hell of a time getting them right, and I finally figured out that the bolt holes were misaligned. "Can't be, never happen" from the company. Finally I convinced them to send me another head, and when they got mine back, they could charge me if they thought I was wrong.

Funny, that charge never showed up on my credit card...
 
The trained monkeys who built my Vertex rotary table didn't quite finish the casting, which is surprising because the rest of the fit and finish is great. The bolt holes in the base still has casting flash and were never finished so a 1/2 inch hold down bolt would not go in.

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I didn't want to take the chuck off to bolt it down flat on the table, so I grabbed a chunk of 2 inch round aluminium, drilled a 1/2 inch hole through it, and bolted it to the table

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Flipped the RT upside down and tightened the chuck on the post. Milled the slots out and life is good now :)

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