What Makes a Nut Tighten on a Bolt?

[FndMech]

I ask this question because I'm in the deep foundation drilling industry, and I use 5" o.d. threaded, hollow bar that couple together in 10' sections. Each bar weighs 200 lbs and the machine that installs these bars uses extremely high torque while integrating a percussion hammer. To say the least, removing the bar from the drill to add a new 10' is extremely difficult. There are hydraulic clamps on some of my machines that clamp the bar and rotate the drill free. Some drill rigs only have one clamp, therefor I use a 36" pipe wrench with a 6' cheater bar and about 5 guys to break the bar loose. After doing so, the pipe wrench teeth are toast. I'm wondering...

1.) parts of a hollow threaded pipe bond with a coupler that make it so difficult to remove? Is it the outside edges of the threads? The thickness of the threads? The friction between the top of the pipe and whatever it hits inside the coupler? I'm wondering if I could grind the threads down in some way that would allow the pipe and coupler not to bond whatsoever?

2.) Has anyone seen any industrial wrenches or tools that would unbind a pipe connection like this?

 

[hydtools]

Are you using thread grease?

Ted

 

[FndMech]

Yes, I use cal-bronze, which is known to be some of the best grease.

 

[hydromarine]

Use a Iron Roughneck pm if you require

 

[dik]

If the threads are 'locked' because of the torsional friction, then is there some type of vibratory impact that can can be applied to the pipe, much in the same fashion as an impact wrench?

Dik

 

[drawoh]

FndMech,

What material are the bars?

--
JHG

 

[Tmoose]

I think I'd look carefully with a bright light and magnification at the threads and butting faces of the next one that puts up a fight being disassembled. Also at some new ones to see what I'm starting with.

Do the threads do the piloting, or is there a male and female pilor diameter making the joint?

 

[Tmoose]

Hi Fndmech,
The cal-bronze site refers to that product for low to medium duty drilling. I did not see a product listed as suitable for "heavy duty" drilling, but I wonder if there is such a product, and perhaps that is what you need.

repeated torquing and loosening even a carefully made assembly can buff down high spots
"new fasteners using motor oil and other commonly used lubricants such as Moly and EPL typically require 5-7 cycles before final torquing to level out the initial friction..."

http://arp-bolts.com/pages/technical_installation.shtml

I'd try that until tightening feels luxuriously smooth, expecting it might improve the situation.

Does anyone ever try using a thin very hard or even compliant washer between the faces at assembly?

 

[hydtools]

Kopr-Kote works well:

http://www.centuryproducts.net/hdd-products_thread_grease_kopr-kote.html

Ted

 

[MiketheEngineer]

A LOT of WD-40 and maybe some heat??

 

[racookpe1978]

Change your process perhaps? Use a oil drill rig-type screw-on fitting and threads. They transmit very high torques, and are un-screwable by the field hands.

 

[tothepoint]

Are they NPT pipe threads, or standard course threads?

 

[FndMech]

standard course threads