As we have a majority of SS fasteners in our Intermediates Area we use one of the following lubricants/anti-galling compounds on every SS fastener no matter the type or material. We like for the mechanic to coat both the threads and the nut. We really haven't seen any discernible difference in these materials at the lower temperatures.
One word of caution since these materials come in convenient aerosol cans that make application very easy. If you have a lot of hot steam or process lines where one could sit a can on I would limit the materials to the brush top cans. Don't ask me how I know this as I stand here in my copper colored shirt.
Thanks for all replies, more specific we are using pressure vessels @ 5-7 bar (g) with quite a lot of flanges using 316 L bolts/nuts due to external corrosion environment. When changing gaskets we do re tight after 1-3 batches, but we can see after 100-150 batches the bolts are starting get "loose" and a leakage occur. We are not using any lubrication att all today and I thought this can be the reason for leakage(to less torque)after a while. No major vibrations are involved.
Milk of magnesia works for very high temperatures, where oil/grease products would just char and go away. Better than MoM is Boron Nitride powder, or BN mixed with a little water to form a paste. With water added, it has a soapy, slick texture much like graphite. We used both of the above for a vacuum heat exchanger connection that saw temperatures of 1600F routinely.
I think you may have a gasket problem along with a fastener problem.
First off I would recalculate the flange and gasket using A193 B8 Class II bolting instead of the current 316L you are now using. The added strength of the class II fastener coupled with proper tightening will give the better gasket seating stress. I would also take a good look at the gasket selection, both type and material, as you may have a problem with gasket relaxation in time. Depending on the flange design you may also have to go to an energised gasket to handle the cyclic load if the flange will not allow adequate seating stress for the existing gasket.
Here is a BN based lubricant as mention in the post by btrueblood
First, anyone that stands in front of a microwave even when heating water is taking a big risk.
IPA doesn't even get warm, not enough water in it. The BN forms a floculent that will stay suspended.
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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
Did you mean that you never used the stuff as a SS lubricant or never used the stuff personally? I can't remember what it was that Mom used to dose us with Milk of Magnesia for but I've used plenty of the stuff-just never as a SS lubricant.
If you are going for personal use get the flavored kind and get the original, unflavored, bottle for use with fasteners.
Some of the flavors will have a small amount of chlorides to enhance the flavor.
Or buy USP grade MgO in powder form, and mix with water or IPA to form a slurry. But, remember to rewet the stuff before you back the fastener out after it's been hot and dried. Raw, dry MgO powder is somewhat abrasive, and not a lubricant, just something to keep from getting metal-to-metal contact. BN powder is a bit different, it tends to absorb moisture from the air fairly quickly (and can be rewet like the MgO), and when moist/wet is a lubricant.
