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Have you ever thought about what is going on inside a stud when you tighten the nut? I learned about a machine at the Palo Verde Nuclear Power Plant that turned my thinking upside down.
If you are interested, please see
http://rick.sparber.org/SPTX.pdf
Your comments are welcome. All of us are smarter than any one of us.
Thanks,
Rick
rgsparber.ya@gmail.com
Rick.Sparber.org
You Tube Channel: https://www.youtube.com/user/rgsparber1
KG7MQL
Thanks Rick, now that is a interesting idea. Not sure where but I am sure I will use it.
It is interesting to break free a nut.
I wonder if you had a frozen bolt say 3/4" if you drilled and taped the bolt for a 3/8" rod if you could tension the bolt and break it free with tension.
Thanks again.
Ralph
Hi Ralphxyz,Quote:
Originally Posted by Ralphxyz
That is possible, depending of course upon the strength of your 3/8" rod and how tight the 3/4" bolt has been torqued. If the 3/4" bolt has been torqued way past the capabilities of the 3/8" rod, then you would never be able to stretch the 3/4" bolt enough to be able to loosen it. However, if the 3/4" bolt has been torqued within the capabilities of the 3/8" rod, then it should work.
Hi Rick, I have both seen and learned about fastener stretch many times over the years. I worked for over 26 years in a diesel/natural gas-fired power plant. While we never had to contend with something like the pressure vessel described in your article, we did have to work with many large fasteners from 3 1/4" stud nuts and down. We used nut runners and torque multipliers to speed up working with the large fasteners. One of our torque multipliers was capable of over 3000 ft lbs of torque using just the input from a 3/8" drive ratchet or breaker bar and a 2" diameter "reactor" bar. The reactor bar was used to prevent the torque multiplier from spinning and was usually braced against the nearest, strongest support we had in the immediate area. Example: When torquing down the 3 1/4" engine base stud nuts, we braced the reactor bar against the engine block.
Thanks for the article, it was interesting.
very common method for marine diesel engines
Seagoing ship propellers are held on by hollow bolts that are stretched by a hydraulic ram after which the nuts are run down and torqued by a wrench pulled by the dockside crane. The dynomometer on the crane is used to determine the torque loading of the nut. When the appropriate torque is reached the pressure on the ram is released and the nut is on to stay. This technique is used for critical components in other industries as well. Thanks for reminding me of stretched bolts.Quote:
Originally Posted by rgsparber
Builders of high performance engines verify torquing of con-rod bolts in this way; measuring length before and after by micrometer. The calculations for effective torque are bound by diameter, thread pitch, and tensile strength.
Quote:
Originally Posted by Toolmaker51
Yes sir, I helped a cousin build his drag racing engine (BBC 632 CI & 1500 HP) and we used a specially built rod bolt stretch gauge to tighten the rod bolts.
I took one ride in it and that was enough for me. :)
Thanks Rick! We've added your Nut Tightening Tool to our Fastening category, as well as to your builder page: Rick's Homemade Tools. Your receipt:
<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-nut-tightening-tool"><img src="http://www.homemadetools.net/uploads/168569/homemade-nut-tightening-tool.jpeg"/></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-nut-tightening-tool">Nut Tightening Tool</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags">tags: <a href="http://www.homemadetools.net/tag/fasteners">fasteners</a>, <a href="http://www.homemadetools.net/tag/hand-tools">hand tools</a></div> </div> </div> </div>
Hi Rick,
Your posting on pretensioning of bolts brings back old memories which, although a bit off topic, somewhat relate. During the 1970's I worked for Union Carbide (now Dow Chemical) in their Montreal high pressure LDPE (low density polyethylene) plant, among other duties, as a design engineer in the associated compression/reaction/compounding processing units. The ethylene compressors & tubular reactors there operated up to 3000 bar (43,500 psi): the compressors in particular were massive in size with many flanged parts. Needless to say, these pressures far exceeded any ASME pressure flange/fitting standards I.e. greater than class 2500 (425 bar = 6164 psi) so we designed all our own flanges/fittings. Bolted flanges, in particular, were typically tightened using hydraulic bolt tensioners: a) to equalize the shared bolt load, and b) to allow minimum nut torquing as you describe in your posting.
Now I'm just happy to putz away making things on my micro lathe & mill.
Regards,
Gary (kngtek)
Calgary, AB
P.S. I enjoy all your homemadetools & website postings - lots to learn there.
Gary,
I can't imagine dealing with pressures that high. It must have been very satisfying to tame it.
Thanks for the story and kind words,
Rick
Really Gary, that must have been fascinating and challenging. So what would a 12" bolted flange look like and how big were the nuts and bolts?
Ralph
Hi Ralph,
The flanges/bolts at the discharge of the high pressure reciprocating compressor (hyper compressor) are well illustrated in the attached photo extract from the website of Burckhardt (one of the leading high pressure compressor manufacturers).
My guesstimate of the discharge flange components in this picture (reinforced by a fading memory of 1970s recollections) are as follows: flange diameter/thickness/no. of bolts (18"/6"/8), bolt head/bolt diameters (4"/1-1/2"). The suction/discharge flange orientation is top entry/bottom discharge. The full picture shows a 12 cylinder (6 x 6) machine and is part of an brochure on the Burckhardt site (https://www.burckhardtcompression.co...er-compressor/), simply titled 'Hyper Compressor'. The brochure includes a good schematic of the LDPE process and details the major compressor components.
The pressure retaining parts flanges/tubing/piping are typically all fabricated from high strength alloy steel and autofrettaged. The bolts are typically fabricated from high alloy steel, quenched and tempered, with a tensile strength >100,000 psi. The tubular reactor (downstream of the primary/hypercompressors) has an open/close discharge valve (cycling on/off several times/min.) - This combined with pulsating flow from the two stages of compression subjects the pressure retaining parts to pulsating pressures and makes them highly susceptible to fatigue failure (micro cracking at the inner bore). Consequently, these parts are all autofrettaged (pre-operation pressurization) which stresses the inner bore to just below the metal yield stress - This induces residual compressive stresses into the near bore portion, spreads the operational pressure stresses into more of the metal thickness, increases fatigue failure resistance and, importantly, reduces the required metal thickness by a factor of ~1.5.
All the above is, I am sure, more detail than you would ever like to know - A far cry from the materials we hobby machinists use.
Regards,
Gary (kngtek)
Calgary, AB
Attachment 17597
Hey Gary, thanks, you never know, I do mess around with 3D printing and injection molding isn't that far off!!
Wow I can imagine a blow out, pow is a little too little of a word.
Ralph
I saw a movie years ago about the building of the St. Louis Arch. As they added the triangular sections on top of each other, they were connected with long tension rods that were hydraulically pre- stretched and then the nuts were run down and torqued before the tension was relieved.
Talking about bolt stretch, I remember working on old Triumph motorcycles, and the manual said to measure con rod bolt stretch for proper torque. Once stretched, I wonder if those con rod bolts are reusable?
My guess is that the rods would be fine. If pulled so much that they permanently elongated, they would not hold at all. The goal is to keep them like a spring that can snap back.
Re Triumph and others con rod bolts, the official advice is that they are not reusable after having once been stretched. They take a set in use and re stretching them will not give the original specification. It is not worth the risk to skimp on an expensive engine re build for a small item, new nuts as well.
Hi All
This process is also used for reinforced concreate. Such as bridge sections etc. The rebar is pre-stretched within its tensile limit, the concreate is then poured in to the mould. Once set the tension is released and theconcreate structure is then placed in compression. This makes the structure a lot stronger, as concreate likes to be in compression rather than tension. I did use to know the formulas for working out the diameter of rebar, quantity required, cross section of concreate etc to support a known load. (but that was a long, long time ago) I can only just remember Young's modulus now.
Very good explination I found on YouTube https://www.youtube.com/watch?v=vuZcPTp51Zk
The Home Engineer
In the old Triumph motorcycle manuals they had specs for measuring the bolt stretch on con rod bolts. Also, if I remember, during construction of the St. Louis ach, they prestreched the tendon rods between the sections and would run the nuts up snug.
It sure seems to be a more controlled way to do the task. No question about friction changing the measured torque.Quote:
Originally Posted by owen moore
At the nuclear power plant, they do this procedure to save time.
Rick
