Ideas for sight glass material using hose barbs?

I am in the design stage of making a few kettles with all sanitary fittings. The current idea I am working on is the sight glass for the HLT and BK. My plan is to use 90 degree hose barb tri-clover adapter like this:



attached to a ferrule low on the side of the kettle. Some kind of plastic tubing would be connected to the hose barb and run vertically up the side of the kettle and gallon graduations added. My question is, does anyone know what kind of plastic I could use for this design? It needs to be clear, safe at boiling temperatures, and compatible with a hose barb to keep the sanitary design. Would a tin polycarbonate tube work or would that still be too stiff?

I know Sabco uses a similar design for their sight glasses, but they have not responded to my email asking them what they use

Polycarb is going to be way too stiff to use directly on the hose barb I suspect.

could you use a tap and die set to get em to mate up?

If you are going to use barbs, then you should use Silicon hose, stretched tight with another barb on top. It is not clear, however, you can still see fluid levels.

I figured polycarb would be too stiff for a barb...as for the tap and die, I am trying to avoid threads just for ease of cleaning and replacing. I spent about and hour and a half on mcmaster trying to find something similar to the Sabco material and came up empty handed :/

Polycarbonate is super cheap. I say buy a length for a couple bucks, and try heating it to fit over the barbs. It softens pretty easily, so if you could gently heat it without burning it, (heat gun? hair dryer? a hot oil bath?) you should be able to push it on. It needs about 150*C to 200*C to soften without melting....Not sure if a hair dryer held super close will hit that, but a deep fryer with some oil in it would....

Heating polycarb might get it over the barb but it will cool and be too rigid to get off the barb for cleaning, if that's the intention.
Could you use polycarb and a short piece of silicon hose over both the barb and the polycarb tube?

kklowell said:

Heating polycarb might get it over the barb but it will cool and be too rigid to get off the barb for cleaning, if that's the intention.
Could you use polycarb and a short piece of silicon hose over both the barb and the polycarb tube?

Click to expand...

I think that if you tighten the silicon hose over a piece of polycarb would work with a worm drive. I say give it a try with cold water first to see if it leaks, then with warm, hot to see if expansion is a problem.

kklowell said:

Heating polycarb might get it over the barb but it will cool and be too rigid to get off the barb for cleaning, if that's the intention.
Could you use polycarb and a short piece of silicon hose over both the barb and the polycarb tube?

Click to expand...

That's a good idea... I guess I don't care much about cleaning super well on a bk... I'd just snap it off once every 6 months and attach a new one

Polycarbonate is probably going to be my fall back plan. I just don't know if the heating idea would create a watertight seal, and if it does, it still isn't quite as easy to switch out as I would ideally like. I am still holding out to find something similar to the picture above...

kklowell said:

Heating polycarb might get it over the barb but it will cool and be too rigid to get off the barb for cleaning, if that's the intention.
Could you use polycarb and a short piece of silicon hose over both the barb and the polycarb tube?

Click to expand...

not even for cleaning- because polycarbonate has no elasticity it will not work over a barb. once it hardens, if there is any movement in the joint it will either leak or crack. if its soft (like at boiling temperatures) it will just continue to deform like silly putty until it no longer seals. a rigid clamp wont do anything here, if you clamp it down tight the polycarb will just deform to reduce the pressure. you need something like a rubber band that can expand and contract while still applying clamping force if this were to work at all. i would seriously look for another option.

McMaster item number 5195T78

Any thoughts?

The sabco ones, based on the picture, are polycarbonate. There is no other rigid, clear, plastic that I know of. Whether it's ideal for a barb is up for argument for sure, but ideal vs. compromise is always in play.

For something more suited for barbs, check out Teflon FEP. It's expensive but... there goes the compromise. You'd have to support it at the top. I can see something like clamping it to a 1" long piece of 1/2" stainless tubing and then welding a short piece of 1/4" stainless rod between the vessel wall and the tubing to hold it up. You might also make a stainless shroud around the tubing with a tight fit, slotted to make viewable.

thelorax121 said:

McMaster item number 5195T78

Any thoughts?

Click to expand...

Only good for 175F

Oh, one other thought. You could probably get away with polycarbonate without clamping at all. Here's how.

1/2" OD barb, 1" long x 3/8" ID x 1/2" OD silicone tubing (as a bushing/seal), 5/8" ID polycarbonate pushed over it. It would be tricky, but you can conceivably push the silicone bushing half way onto the barb, then push the polycarb onto the non expanded portion and in one motion, push the whole thing down onto the barb.

Is the Teflon FEP tubing clear enough? All I see on Mcmaster is semi-clear, and I want to make sure that will still work for checking water levels in the HLT

Why use the hose barbs at all? Just go with the polycarbonate and thread the ends with a die set. Unscrewing them from a Tri-Clamp to NPT fitting shouldn't be too much of an issue.

I have used Flex Pex for mine they are not clear but work well enough to see water in my HLT.

This is all being over thought, simply connect silicon tubing to two barbs, they do that here in Germany. You can see the fluid level inside.

If you absolutely need the polycarbonate tube, then put it in the middle and connect silicon tubes on each side over the barb, then worm drive over the polycarbonate/silicon connection on both sides for easy cleaning.

I don't think it's being overthought, but I guess I just like to obsess about things. If you do go the silicone between two barbs thing, you could go with very thin wall to keep it as clear as possible. The trouble is adding graduation marking directly on the tube. You'd have to also clamp on a piece of flat bar or something to apply your numbers to.

I thought about a sight glass for my boil kettle, but ended up just getting a long aluminum extrusion and used a dremel to mark off every gallon put into the kettle. Now I just dip my "truth stick" into the kettle every time I want to know how much liquid is in there. Cost about a buck for a 4" L extrusion at Home Despot. I don't leave it in for the full boil, just dip it in periodically to check for evaporation. Good luck on going for a sight glass though, they are pretty cool!

We tried going the dip stick route on our club 55 gallon kettles and it was a total bust. Unless you're boiling near the top of the vessel, you can't see through the steam coming off the wort.

Looking at this FEP tubing, any idea if it is soft enough to work with stainless barbs? It seems like it should be stiff enough to stay upright on its own.

McMaster 52355K17

I'd just use thin silicon tubing with...