Torque Multiplier

What does it say on the calibration certificate?

<...Torque Multiplier...>

Isn't that just a fancy name for a "reduction gearbox"?

May we assume you're talking about something like these?

If so, it should work for your application if there is a good, secure place for the reaction bar to rest. 2 things:

1. Make sure the bolt/studs are lubricated before starting assembly,

2. Tighten the nuts evenly, in a pattern to spread the force, and in stages,

3. Get rid of the impact wrench for assembly - may be useful in disassembly. Ok, that's 3.

ok, this sounds reasonable

personally i think the bolts are being grossly over-torqued this is what i need to find out.

We are replacing the die with a temporary die in july at shut down and sending this one out for repairs. metal has been passed through the extruder and scored the die. I'm going to pick their brains for a procedure.

thx

Yes we use a torque multipliers fitting wheel nuts to our semi trailers they work well just remember it tested and recalibrated regularly.

hmmm, this has been on a shelf for some time and if it was used it was used by hacks trust me! good point!!

Use exactly the correct lubricant, and remember that the reaction point will be taking the full (very large) force. Beware chains!

This I need to find out. The used never seize on the last go round. i will check the specs

thx

So what do you suggest using on 30 Bolts to be torqued to 800ft lbs?

The manufacturer must recommend one. i will call them today thx

There have been some interesting threads regarding Torque on the various forums floating around. If I get a chance, I will look around after work tonight and pass them on.

For example: http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=torque&order=asc

I will search around for more, plus a specification or 2 and post through 4Shared.

Respectfully,

qaqcpipeman

I would really appreciate that as i'm sure the others. There are so many variables to take into consideration if you are even going to be close. I have worked with some of the best in the maritime industry over the years but the best i seem to find are right here!

Thanks so much to All of You,

I'm going to tackle the manufacturers specs on this. There must be a torque sequence as well a procedure. this is the wrench we have:

This has been enlightening thank you

This is made by CDI Torque Products 10:1 @ 2000ft lbs.

800 ft-lb? That's a bunch. I thought my trailer hitch ball was a lot at 250 ft-lb!

Consider using a "Super bolt." This may generically be called a jack bolt. It has several smaller bolts surrounding a large bolt. You do not torque the large bolt, just snug it; then torque the small ones to get the clamp load you need.

I think there is also a hydraulic torque wrench, but I don't know what clearances it needs.

I do use those here but for this application its not feasible. I am going to pull up some specs on this. There have been some very enlightening do's and dont's tossed around.

I guess i would like to see if there is some sort of industry procedural standard so i can pass that along.

Enerpak manufacturers hydraulically driven torque wrenches, but they are very expensive. If you are experiencing problems, this might be a solution. They require a stationary point to push against, and they are heavy. But the size is not too bad. Common on underground pipe flange tightening. Good luck.

Good reply. Clamp load is what we are after.

You (of course) are right on the money with your response. The problem with that method, is that any replacement of bolts would invalidate the existing measurements, unless identical bolts were used. Additionally, there is the question of permanent bolt stretch. Would the system require new bolts each time? Is there a point where the bolts have stretched beyond their limits?

How would you suggest that a facility that must clamp and re-clamp continuously approach the issue?

"any replacement of bolts would invalidate the existing measurements"

Well yes, of course! Furthermore "identical bolts" are never identical when one looks (for example) for an elongation of .020" or so. This is why every bolt must be measured prior to tightening. After tightening, every bolt is re-measured. When using the specialized instrumentation, all readings are recorded in the device's memory. Thus, we can check for migration of bolt loads months later by simply pulling up the proper fastener ID in the unit and then measuring again. Thereby, anything which is out of tolerance can be "tuned" back to spec before it breaks or causes leakage

Most people don't understand that all bolts stretch when they are tightened. If they didn't you'd never be able to have a tight bolt! In essence, bolts act as springs; The tighter the spring, the more the clamp load. This stretch is directly proportional to bolt stress up to the Yield Point. If the fasteners are to be re-used (ie if the component is to be dis-assembled and then re-assembled), they should never be stretched beyond Yield. However, in some cases tightening beyond yield is actually required.

First part: As long as the stretch is within the elastic limits, it should return to the pre-stretch length when the load is removed. This would include deformation of the threads, and I don't know if this is possible to determine.

Second part: Hasn't been mentioned yet that I have seen. How about heating to achieve some elongation, then snugging the nut including torque to assure things are seated, then when the bolt cools a load will be applied? Sort of like using hot rivets in structural framing.

1: "I don't know if this is possible to determine". Indeed it is. You simply just measure it again. If this reading is the same as your initial reference measurement, the fastener hasn't yielded!

2."How about heating to achieve some elongation". This is typically practised on large fasteners such as those found on steam turbines and metal-forming presses. It requires a hole machined down the centre of the fastener into which a heating rod (gas, resistance or induction) is inserted. Another problem with this is that you have to wait for everything to cool down to ambient before measuring elongation. Not so good when you have a plant to run! With everything considered, the method isn't practical for this application. The required preload is low enough so that common tightening tools can be used.

...as far as the heating part is concerned the bolts aren't torqued all the way until the die is up to operating temperature ie bolts as well. This has been a very low tech operation thus far. I'm blown away by all the considerations as well as the technical expertise of those like yourself Lehman57 thank you

@ Lauruz: Here's another option for you to consider...

These bolts change colour when the proper preload has been applied. They are factory-calibrated so that the indicator window becomes fully black once the correct bolt stress has been acheived. Thus, regardless of the input torque, you'll know that the fasteners have been tightened properly. Furthermore, you wouldn't even need to use a torque-indicating wrench.

The only cavaet with this type of bolt is that the colour change is subjective. You'll have to know how "black" black really is. For highly critical applications, bolt elongation measurement still provides a much better method of controlling bolt load (and, it provides a full process audit record). Nevertheless, for something like your dies, this could be an acceptable alternative.

Considering we do have 30 bolts holding this thing together this may be a viable consideration but the bolts are recessed and Allen heads. I'm afraid that someone is going to get hurt with the present method they are using (two men and a big azz bar) this scares me. We are not stranded up in the Klondike!

I will be contacting you for quotes :)

Considering all that I have read here this seems to be the most plausible answer. However, applying it to my current die is another issue in itself. The bolt heads protruding above the die face is not an issue, it would require spacers.

I'm very interested in the hydraulic torque tools you sport on your web site. It looks like high quality tools.

Hydraulic torque wrenches are indeed very useful. However, I think that in shops where the number of relatively high-load bolted joints is few or where frequency of use is low, they may be a bit of an overkill since, as somebody had mentioned earlier, they can be quite expensive.

If you're confident that the torque multiplier will be used in a safe manner, you may wish to save some money and tighten your bolts with it, rather than with something new. A pneumatic torque wrench (these are different animals than pneumatic impact guns), on the other hand, would be a better choice if the thought of the multiplier gives you concern. This variant develops a slow and easy rotation of the fastener rather than the "give 'er hell" explosion of uncontrolled energy that you'll get from an impact gun. The former is advantageous for fine adjustments of preload.

The important point to keep in mind is that any bolt tightening tool would work (including the use of the old "cheater bar"!) as long as one then also uses a proper method to verify and tune the preload.

1st, I can't believe you would even mention the unsafe cheater bar, as some might consider it a recommendation and that you condone it's use. I have seen many bruised hands & other body parts, a few concussions, and some broken body joints with a cheater bar slipping. Catch you using one during a visit to for one of my clients doing QA or QC and I will NOT accept your finished product until you disassemble and re-torque to my satisfaction. Proper torque application is a science, let's explore it safely.

The vendor that I had a residence contract with last year for Shell Appalachia bought a Hi-Torque Hydraulic wrench with 4 sockets to safe money. Twas funny that 2 hands could torque the old way, but they needed 4 to run the machine, and with slippage, odd angles, and just putting anyone on the tool, it was found after an intensive time study that it took twice as long to assemble the GPUs they were building.

That was our experience too.........

I think the owner of the shop just liked toys. I tried to set up a meeting with the salesman to discuss Shell's needs, but he could not wait to get out of the shop.

His sales office was within a 1/2 a mile from our PA Headquarters. That effort added one more level of concern and my contiued avoidance of the companies who sell the products to minimize the efforts of torquing.

I may have missed the comment on torquing sequence, if they were made, but that is another most important part of a great torquing program.

I don't think torquing sequence was mentioned, but it certainly is important. Sequence should be a criss-cross, not every one in line. Also tightening should be in several steps, not all at once.

Here is a link to an Installation Procedure.

http://www.4shared.com/office/HIquF6Rr/Installation_Procedure_For_Hig.html

I am sure everyone has a chart with patterns that are usually used.

This procedure is for structural bolting in which the focus is shear control rather than clamp control. Sometimes, such procedures also address the latter. However, the civil engineer's approach to this issue has got to be one of the most ridiculous: Their QA is based on the fastener having to be "snug tight" before the next step in the procedure. The latter is, in fact, quite accurate but since it depends on the subjectivity of the former, the end result of the process is fraught with overall uncertainty

Don't get too hung-up on "pattern tightening". It alone alone will not ensure accuracy of bolt load. Its true benefit is promotion of even joint/gasket compression and thus avoiding "cocking" which can bind a joint or damage a gasket. On large flanges, a very effective alternative is to use bolt tensioners which can tighten at least 50% of a flange's fasteners simultaneously (under certain conditions, even 100% of the fasteners can be tightened at the same time).

I am usually loathe to work with firms that promote tensioning equipment, because working with Westinghouse Nuclear on some of the 1st tensioners many years ago, I seen the propensity for overstretching bolts and even needing massive hydraulic equipment to remove a tensioned bolt. Could have been many reasons, but another company near me, previously called Bolt-Tech, now owned by Mannings has even recently created problems for facilities that I worked on.

This has been an interesting thread, but maybe we are overworking it.

No no, please continue. I have been concerned for years about the licence plates on my car falling off. ( Just kidding, this thread has taught me things about the subject I did not know, and I thought I was on top of things understanding bolt stretch.)

I come may be a bit late but I think that there are some remarks to be done:

- if you had a bad experience many years ago that does not mean that today's tensioners are as the 1st versions so may be you should review your position

- if a tensioner overstretch a bolt this ONLY due to the wrong usage made by un skilled personnel since the device brings ONLY the force to stretch and if this is too big then the user programmed it so. This in fact the advantage of hydraulic tensioning since several bolts can be loaded with equal forces (within the friction and dimensional dispersion of hydraulic cylinders used ) as pressure is in the system every where the same. Which is not the case of torquing.

- for big bolts tensioning is the best approach if it is justified (I apologize if I support a principle you do not like but I think one has to be objective).

- the pulling force to stretch the bolt so that the nut will become free is the SAME as the one used to stretch it at assembly I do not understand why the systems to remove the bolt have to be more massive than the one used to generate the initial stretching.

- in fact there is NOT a generally valid BEST solution for tightening ! The solution depends on many factors as how important is the assembly, how dynamic is the load, how often the assembly will be disassembled and reassembled, if the same bolt has to be reused or every time a new one must be tightened and so on, the list goes on the last but not least criterion being economical since the cost has to match the needs.

- there are procedures which can reduce the uncertainty of preloading when bolts are torqued (Boltintegrity does not like it since he is more involved in tensioning), the most current one is the torque-angle procedure which is based on a limited torquing (usually up to 1/5 - 1/3 of the torque estimated for the final preload) and a tightening by angle to the end preload. This procedure decreases in an important way the uncertainty and has the advantage to use classical tools (any type of torquing tool) and a short operation time since the installation of the tightening devices is not always so short as it is claimed.

- a last remark not related to your comments but to an other: the thread deformation does not influence in any way the length of the bolt under stress, in such measurements one does not take the parts as reference but the OTHER end of the bolt and this bolt "core" is parallel to the threads not in series so that ... the uncertainty is ONLY related to the parallelism of the 2 ends and the un-precision of the used device.

- it would be of great interest to know what kind of problems were created by Bolt-Tech / Mannings it could happen that either tensioner' s concept or personnel skills or even procedures were bad. If it would be as you claim the number of places where tensioning is used would not be so huge in many industrial directions.

As for the concerned application I consider that the use of a torque amplifier could be the optimal solution if the uniformity of the preload has not to be very high. The problem is more in the direction of the assembly-disassembly-reassembly of the tool.

The specific load on the threads flank are very high if the bolt is designed in an economical way. I made myself some tests to determine how friction grows up as function of tightening operations on same bolts. If the lubrication is not the right one the friction becomes such that the preload after about 4 operations is no mote than 1/4 of the first obtained value. I think this is an aspect to be considered as important and which could lead to other solutions. An estimation should be done. With a high pressure lubrication (MoS2 or Graphite or PTFE and a grease matched with the temperature) a bolt can be used many more times but not for ever!

I have dealt with everything from cheap imported non calibrated wrenches through "SuperBolt" (based near me in Carnegie, PA), high torque devices, hydraulic multi head devices to Tensioning studs in Nuclear Power Plants.

The more I seen, the more misconceptions I discovered, many improperly assembled machines and devices, the more intrigued I became, making a study and doing many tests on my own.

I am not well convinced of the accuracy of the cutesy dye releasing devices or the press film type indicators on the market, but I won't belittle them.

Any manufacturer, engineering firm, or constructor worth their salt should have a great procedure in place.

One that identifies the seriousness of the need, the safety issues involved, and a truly realistic view of what is desired and required.

I see misconceptions with almost all vendors, and a lot of it is caused by bad verbiage or not explaining the intent.

For example, about 3 months ago I generated an NCR against an International Company while doing Quality Assurance for an International E&G Firm.

The intent was there, and I understood it, but the verbiage was so bad that arguments began and are ongoing.

We are talking about a Billion Dollar Project at a standstill!

Would it be practical to employ pneumatic clamping? Certainly expensive to convert to, but, the savings in labor, and consistency would soon cover that cost I would think.

This item can pull 16,000 lbs. The company listed might have some solutions for you. Pneumatic/Hydraulic Straight-Line Action Clamps

Description: Straight Line Clamps; Port Size: 1/8 NPT; Holding Capacity: 16,000; Type: Straight Line Action Clamps; No Description: 21; No Description: 2-3/4; No Description: 1

/ProductImages/8930530-11.jpg Add To Cart Add to List Email To A Friend Print this page

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]Nothing more than a bolt would appear to have any practicality in our die..its bolts or bust due to a variety of factors. Not to mention it operates at around 400 degrees. I will keep this in mind for other projects though.

At 400 degrees, it would need to hydraulics, not pneumatics, The beauty of this type of clamping is the speed, accuracy, and repeatability.