Originally Posted by
Eagle
I worked in the USA for a number of years and part of this was working as a senior engineering instructor for BP Oil in Ohio. My job centered in the maintenance section in the main workshop. One day the men had dismantled an enormous four cylinder flat horizontally opposed ammonia compressor. It was designed similarly to a VW engine but about 5 meters wide. The bolts that held the cylinder heads down were about 32 mm in dia. or maybe even 38 mm. The length of these bolts were equal to the width of the compressor.
As I walked past I noticed that the men were applying Anti-sieze onto the threads of the bolts and into the nuts. I knew from experience that this was not just wrong but extremely dangerous to do. To prove this to the engineering boffins, I sent some emails to two of the major bolt and fastener companies and asked them about this procedure. The following is their basic reply.
Anti-sieze should NEVER be applied to ANY bolt that is highly stressed. The problem is that it is TOO slippery. New bolts and nuts (high quality bolts and nuts) come supplied with a certain amount of lubricant already applied to the threads. This is a maximum amount that will ensure the CORRECT tension on the bolt when torqued up to its design stress. If the threads on the bolt and or nut, are covered in anti-sieze, the extreme lubricating ability of the goo will nullify the torque loads on the bolt. What this means is that if you set the torque wrench to a specific torque stress, the lubricant will allow the nut to be rotated so easily that a MINIMUM torque stress will be applied as a factor of THREE to FIVE times or more. This means that a torque setting of say, 100 ft lbs, can now be at a minimum of 300 to 500 ft lbs.
To tension a high tensile bolt to 5 times greater than its designed load will stress the bolt almost to its breaking point. If a wheel stud is stressed like this, it only needs a sharp shock (like a bump in the road) and the extra loading will snap the bolt. If your "lucky", the bolt/stud will snap before the wheel is used on the road. Anti-sieze should NEVER be used on wheel studs or any stud/bolt where it's essential the correct tension is applied. As well as allowing the nuts to be rotated to a higher torque, they can also undo much easier from vibration and impact loads. Has anyone ever had wheel studs shear off or essential bolts snap? Did you apply Anti-sieze to the threads when you torqued up the nuts? The only place where Anti-sieze works properly is on the studs and nuts that hold the exhaust manifold onto the engine of your car or truck. There are of course many areas where Anti-sieze can be used but it certainly needs care and consideration. It must never be used on a highly stressed part like a bolt.
When I passed the emails from the bolt manufactures to the engineering boffins at the BP Oil refinery, they became very excited, it caused a major maintenance control program to be enacted immediately. It doesn't need much imagination to realise what could have happened if a high pressure, high volume ammonia gas compressor had exploded.
So what lubricant can you use on wheel studs and nuts? You need a lubricant that matches that used on a new bolt. You MIGHT be able to use a lubricant from a spray can but be careful what you choose. To protect the EXPOSED threads of the wheel stud after the nuts have been tightened, you can coat the exposed threads with a light coating of "Silver Fross" paint. This is an aluminium type of paint but I haven't seen it for some years. I used to use in on my aeroplanes and it worked well. Whatever you choose to coat the exposed threads with is your choice and your responsibility.
I hope this info will assist you and be of help.
Eagle
Reply With Quote
Posting Permissions
