When you really want to have welded-in ports on your vessels but can't find a competent welder, this fitting is the next best thing if you're willing to do some soldering. The tricky part about soldering fittings into the thin walls of pots and kegs is the extremely minimal contact area which does not allow for enough strength. Using these fittings, along with a our reusable install tool, you'll create a tight fitting joint with loads of contact area that is ready for a highly effective silver solder job.
The fitting has 1/2" NPT male threads on one end and 1/2" compression on the other. The typical use would be to install it into a vessel with the male threads facing out for direct threading of a ball valve. The compression on the inside would then accommodate a diptube or HERMS coil. The orientation may also be reversed if you can think of a reason to do so. The machined chamfer on the leading edge of the fitting allows it to enlarge its own hole.
This fitting is also available with a bent SS tubing diputube elsewhere on this site.
Here's how it gets installed (assuming male threads outward):
- Drill a 13/16" hole in your pot (while 13/16" is ideal, you can use 3/4" or 7/8" as well. 7/8 is recommended for thicker wall material).
- Deburr the hole (file or sand the sharp edges),
- Degrease the fitting and pot wall with paint thinner, acetone, etc.
- Remove the compression nut from the fitting, remove the internal ferrules, then thread compression nut back on until it bottoms out.
- Remove the nut and washer from the install tool and then insert the bolt of the install tool into the PTbulkhead fitting until the large diameter die contacts the pot wall.
- On the inside of the pot, install the washer and thread on the nut until hand snug. Jiggle the install tool from outside to ensure the die is not jammed up off center. If it loosens up, re-snug the nut hand tight again.
- Apply liquid flux to the fitting on the inside of the pot. This will ensure flux coverage when the fitting is pulled into place, but also acts as a lubricant.
- With a pair of wrenches of some sort, tighten the bolt/nut to pull the fitting through the hole until the large ring at the female end of the fitting makes contact with the inside of the pot wall.
- Be sure not to over pull the fitting because it is possible to open the hole up too much such that the fitting is not longer a tight fit!
- We find it best at this point to prop the pot up between two saw horses or something similar with the male side of the fitting facing down so that the solder will pool evenly. Apply a little more flux, heat with a propane torch and apply Stay Brite silver solder to the joint on the inside of the pot.
- After letting the joint naturally cool for about 15 minutes, clean up the area and polish the heat affected areas with bar keeper's friend or a felt wheel with polishing compound to return the area to the original luster. Note that the burnt flux is water soluble so aggressive solvents are not necessary.
The install tool is available separately as an accessory. It can be used over and over to install many PTbulkhead fittings.
NOTE: Stainless steel cannot be soldered to aluminum pots. Also, you cannot use standard plumbing flux found in big box stores. You MUST use special liquid acid flux such as found in our accessory silver soldering kits when soldering stainless steel together or to brass or copper.
This fitting is "Bore Through" meaning a 1/2" OD tube will slide all the way through if you want it to.
Stainless Steel Ferrules: Many customers want to use SS ferrules for strength. We find that nylon ferrules are fine for almost all applications including HERMS coils as they seal onto tubing without having to overly torque the compression nut. If you choose stainless ferrules, please first understand how they work.
The compression nut on this fitting will need to be tightened much tighter than you are thinking in order to swage the thin SS ferrule into the surface of the SS tubing. Go ahead. Picture how tight you'll make that nut. Nope. Way tighter sir. When the pull through fittings are installed in the pot, there is no easy way to swage the ferrules because your HERMS coil will be in the way of tightening the nut as tight as you need to and there's no wrench flats on the fitting itself and you would likely tear the solder joint apart if you're not careful.
OK, you understand but you still want to use SS ferrules. Here's the only way we can figure getting it done. First, make sure the area of your SS tubing that will sit inside the compression fitting is perfectly round and smooth. Since most of this tubing is seam welded, there may be a tiny ridge down the weld line. Sand this ridge smooth to reduce the amount of effort in the following steps. You MUST purchase another 1/2" tube compression fitting such as the 1/2" NPT x 1/2" tubing compression to use temporarily as a swaging tool. I know it's confusing but bear with me.
Take the fitting apart, lubricate all the parts on the compression side (threads, ferrules) and also the SS tubing. We recommend something like keg lube or Vaseline. Assemble the fitting again with the ferrules' narrowing cones facing the fitting. Insert the tube to the depth desired and then swage the ferrules using two large wrenches. You'll know you have them swaged when you are unable to remove the thin ferrule off of the tubing when the fitting is taken apart. If that thin ferrule is still able to slide on the tubing, you didn't tighten it enough.
Once you get it swaged, now you can remove that standard fitting and use it to swage any other ferrules. In the case of a HERMS coil, you'll swage the ferrules on both in/out leads and then you can move the coil into the pot where you already have the pull through bodies installed and soldered. Once the ferrules are swaged, it will not take much torque on subsequent installs to make them seal into the fitting.
Or you can just use nylon ferrules.
WARNING: We have only
tested this process (and continue to use this method) on holes made with our
tungsten carbide hole saw bits. Other methods may be used to make clean holes
but methods that work-harden the opening of the hole may make it brittle and
prone to splitting when the pull through fitting is forced in. We have had a
limited number of reports of punch and dies causing this problem but we are
unable to repeat it here in the shop. We will not accept responsibility for
damaged pots in any circumstance.