Torque Values for Tightening Bolts

I assume you know to what value you wish to torque the bolts, yes? These bolts are not hydraulic bolts or studs, rather, you are going to use a hydraulic wrench, correct?

If you answer in the affirmative to both of the above, then, when you get the hydraulic unit, there will be a chart supplied with it that lists the hydraulic pressures applied to the wrench and the corresponding torque values for each pressure. This relationship of pressure to torque varies between manufacturers and models.

The sequence and stages of torquing the bolts is dependent on what is being torqued and to what value.

Plan on renting the tool as they are very expensive for a one time use.

thank you mareng for the information.

actually i wanted to know if i have the specifications of the bolts to be impact wrenched, then how come i know the torque required to tighten them without damaging the nuts or the the bolt itself.

"Impact" is another matter altogether. Not sure there is a 100% reliable way to torque by impacting--so many variables. For example, after many bad experiences, whenever I need tire rotation and balance, I always demand hand torquing of my lug nuts (same for bolts on some cars), and request it to be written along with torque value on the work order--or write it on the order myself at time of signing. Since I started this practice, have never had siezed, frozen, damaged or unremovable nuts/bolts. Before this, chances of proper torquing and avoiding "damage" was 50:50 at best. Some shops will calibrate daily, most probably don't.

Maybe this is off thread for your request? But if you seek the info as a means of speeding up service workflow, or dumbing down employee skill requirement (and thereby avoid training), it might be wise to think again. Better to undertorque with impact and finish with torque wrench.

As mentioned by a couple of guests (come on guys, sign up), tightening a fastener with an impact wrench is not a particularly accurate way of torquing. I'm sure there are some pneumatic impact wrenches that are made for specific applications, but I've never seen them.

I like the suggestion of taking the bolts up with an impact wrench and then doing the final torquing with a proper torque wrench.

But, lets say you had 600 fasteners to tighten and had a range in which to tighten them, say 90 to 110 foot pounds. You could do this by adjusting the control valve on the wrench or adjusting the air pressure supply. One very important thing, however, is to have a regulated air supply to the wrench because the air compressor will cycle and vary the output to the wrench and give different torques as a result. The regulation pressure would be best set below the cut in pressure of the compressor to avoid under-torquing. I would also check every 10th fastener with a torque wrench to be sure you're in the range.

To accurately tighten bolts with an impact wrench - DO NOT USE directly from an air compressor- as it will not allow precise air pressure and proper cfm. I have designed several impact wrenches for special applications including the use of NASCAR race teams to tighten the lugnuts to 92 to 97 ft.lbs of torque. We have done this using Nitrogen powered and regulated power system. This system allows for the speed and accuracy required for that special application. You will not see any race team using a torque wrench during a 13 second pit stop.. If you need more information contact me.. We still provide special application design in the air tool impact wrench field from 1/4" drive thru to 3-1/2" drives of industrial 80,000 ft. lbs impact-tools. We have designed and put in use impact wrenches that would tighten over 1000 nuts and bolts within a given sequence and time frame.. It is a fun and I enjoy my work a lot and have been doing it over 45 years now..

Later.. Ken

Hi,

If you require Torque Table for Flanges, Garlock joints i can send you. Please write an e-mail to me at prakash.kulkarni@dolphinenergy.com

You can use torsion control bolts, or TC Bolts.

They have a torx male stud at the end of each bolt which is designed to break at exactly the desired, engineered torque, when impacted by a certified instrument.

Each impact tool is application specific. I do not think you can buy them.

Last I heard, they rent; only and require re-certification often.

Iron Workers use this system for structural steel erection, so engineers can be 5 nines assured of a quality connection.

My grandfather used to jump on his spud wrench three times, as he weighed 150 lbs. He assumed the "extra jump" exceeded 300 psi. It worked for years.

This was not "good enough" for Mass Mutual, who I believe owns the patent on the tool or re-insured the original third party certification laboratory; as the story goes.

Jumpin' on the spud wrench... lol! I imagine a scene with dozens of burly construction workers all hopping up and down on their tools...

Torque (Suggested Values)

The question should never be "how strong is the bolt?", but "how much load can we safely apply for maximum performance and safety?"

Torque is the product of Force x Distance and is expressed in inch-pounds, foot-pounds or Newton- Meters (metric). For instance, a foot-pound is a one pound pull on a wrench handle which is 12" away from the centerline of the bolt. Remember that most printed torque values are for clean, dry and plated bolts, and are based on tightening the nut onto the bolt unless otherwise noted, such as with socket head cap screws. That's because torquing the hex head of the bolt can require as much as 20% more torque to allow for the relaxation of the twisted shank.

A torque wrench is nothing more than a calibrated elbow. It tells you what your elbow feels, which is the friction of the rotating bolt head or nut against the work surface, along with the galling of threads under pressure, as they are trying to stretch the bolt. Tests have proven that 90% of initial work energy is consumed by friction, which leaves only 10% to stretch the bolt. Friction must first be overcome before the bolt can stretch.

Proof load is the maximum safe load that can be applied to a fastener before it experiences permanent change of length or yield. Once the joint is together, any further rotation of the bolt head or nut puts a torsional twist to the bolt while it is being stretched.

Washers

Flat washers are often overlooked for their importance in providing an even bearing surface to distribute concentrated stress loads over a wide area. Washers come either in Plain (soft steel) or Hardened versions. Washers do not come in different grades.

Vibration Considerations

Simply stated, a connection will vibrate and loosen if it is not tight enough. A fastener will not feel any increase in load until the service load of the joint exceeds the pre-load or clamping force. Therefore, if a bolt is producing more clamp load then the service load, the joint will not separate. However, even a properly torqued joint can vibrate loose from dynamic or cycling loads if the joint is not fully compressed.

Excerpt Taken from EZ Facts Safety Info

You can call your local Garlock supplier or your bolt supplier and they will have charts that you can pick your torque valves from.

This site maybe of some use.

http://www.garlock.net/ViewSolutionsPage?page=torqueTables

Hydraulic? Do you mean, pneumatic?

to be honest i meant both.

hydratightening and pneumatic wrenching.

which ever you can give me feed back on would be great.