peakbagger
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Just in case you need to replace a tube fitting on the SEE air lines , they appear to be 10 MM metric bite type fittings. The tricky part is that these fittings are made in different pressure ratings. The pressure rating you want is a "S" rating rather than a "L" rating. The L rating fittings are physically larger and will not interchange with the S fittings used on the SEE.
I picked up some copper nickel tubing to replace the steel lines. There is a tech bulletin from the military that the air line that runs from the air pressure regulator on the passenger side of the truck to the air tanks rusts out and fails due to condensate buildup and the military recommended stainless for a replacement. I have elected to use the copper nickel lines as they are easier to work with then stainless while having good reputation for corrosion resistance and less prone to cracking due to vibration. I may also install a low point drain on the line at some point. When working on the air pressure regulator, I found obvious corrosion inside the fittings so I expect this is potential long term issue to keep an eye on.
Do note in addition to the metric bite fittings, there are also BSPP fittings used on some locations and many of the components. These have an intermediate gasket for sealing and have a straight thread and fairly easy to spot.
A thread pitch gauge and caliper is definitely recommended for figuring out what you have got as 10 MM is fairly close to 3/8 tubing. Standard Swagelok type fittings in metric tube sizes are not interchangeable with the metric bite fittings as the threads are not the same pitch as the metric fittings. They will start to thread on but I expect if someone forces it, they will ruin both the thread on the fitting and the backup nut. I have not checked if the double ferrule swageloks will seat in crush type fitting seats used on the metric fittings. They look close.
I picked up some copper nickel tubing to replace the steel lines. There is a tech bulletin from the military that the air line that runs from the air pressure regulator on the passenger side of the truck to the air tanks rusts out and fails due to condensate buildup and the military recommended stainless for a replacement. I have elected to use the copper nickel lines as they are easier to work with then stainless while having good reputation for corrosion resistance and less prone to cracking due to vibration. I may also install a low point drain on the line at some point. When working on the air pressure regulator, I found obvious corrosion inside the fittings so I expect this is potential long term issue to keep an eye on.
Do note in addition to the metric bite fittings, there are also BSPP fittings used on some locations and many of the components. These have an intermediate gasket for sealing and have a straight thread and fairly easy to spot.
A thread pitch gauge and caliper is definitely recommended for figuring out what you have got as 10 MM is fairly close to 3/8 tubing. Standard Swagelok type fittings in metric tube sizes are not interchangeable with the metric bite fittings as the threads are not the same pitch as the metric fittings. They will start to thread on but I expect if someone forces it, they will ruin both the thread on the fitting and the backup nut. I have not checked if the double ferrule swageloks will seat in crush type fitting seats used on the metric fittings. They look close.