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Discussion Starter #1
My oxalic acid vaporizer is leaving a lot of re-condensed OA residue in the hive just beyond the nozzle. I disassembled the hive about an hour after treatment and found what looked like about half of the dose condensed a couple of inches beyond where the nozzle would have been. Is that normal? If not, what should I do about it?
 

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Discussion Starter #3 (Edited)
Front of hive. I've also used a shim with a hole to insert it on the side near the top, I've noticed residue on the frames when I removed the shim and put supers back on but it didn't seem to be as noticeable. I just realized I didn't look under the cover to see what was there.
 

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Discussion Starter #5
It is a homemade version of the provap using a cook pot I machined. The cookpot is 35mm OD to fit a band heater (same as on the really long thread about them) with a 1" bore and fitted with a 3" long 1/8" nozzle, nozzle is tight to the heater.

I do have an idea for making a power ventilated vaporizer so I have ordered material to make a second cook pot but I'd like to address any shortcoming this is having. I'm thinking that having a residue spot is probably not normal.
 

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I think that the residue you see is mainly from the water of crystallization condensing into the OAV, perhaps your temp could be a bit higher or perhaps your nozzle is too long. I think you will always end up with some residue.
 

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Discussion Starter #8
That might be. I am using oxalic acid di-hydrate. I had trouble getting finding OA anhydride back when I bought it a few years ago. Now I know where to get AO anhydride but I've already got a big tub of the di-hydrate stuff. My controller has a timed ramp/soak profile, I have a short soak at 250°F (120°C) while the water bond breaks and boils off, then I continue to 320°F (160°C). When I ramp up with the nozzle visible I can see the water boil off, then nothing, and then the vapor so I'm confident that is working.

I made my vaporizer so I can insert it, plug it in, and then step away several feet so that I don't get a whiff or need a respirator, since I'm a controls engineer using a temperature profile was trivial.

I'm thinking I should run a test this evening to see how much residue there is if any if I stop the heat right after the water boils off before sublimation.
 

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Discussion Starter #9
perhaps your nozzle is too long.
My nozzle is 1/8" ID brass pipe tapped into the cook pot. The ID of the 3/16" copper tubing you used is .128, so our nozzles are the same inside size but I need to shorten mine. I think on the next pot I'm machining I'll also place the nozzle lower so it exits between the heater clamps. My cook pot also increases in OD below the hot zone to make a base to mount it on, I think on the new one I will machine the OD down to decrease heat conduction away from the bottom and mount it differently. I think another problem is that to get the nozzle into the hive opening I have to raise the back up, which angles the nozzle at the bottom board. I need to put a bend in the nozzle. I will give these a try this evening.
 

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I found that when I lowered the nozzle that I had a greater tendancy of spraying out un- sublimated oxalic acid and did not get such a fine crystal fog, also found the same when the nozzle diameter was increased so I settled on the 1/8" ID 3//16" OD refigeration copper tube, but no more than 2" long.
 

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Residue will form if there's a solid surface around the output of the nozzel.

Drill a new hole in a location you can be certain there will be no solid objects.
 

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I have the provap 110. I was using the CRY oxalic acid in the tall plastic container be it seemed to leave a residue. I went back to using the sograns (sp?) wood bleach and it seemed to me to work better.

so the issue is incomplete sublimation of your dose of OA. Could be a number of reasons, but an educated guess would be consistent and adequate temperature range to cook off the 2grams of OA.

the end of you contraption should be long enough to enter the cavity of your hive. If not, any molten OA recrystallizes when it cools and will cause issues later.
 

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61439

OA build-up. The end of the nozzle would encounter oa blobs from the last treatment which would impede the subsequent oa vapors and compound the problem.
61440

I went in and made sure the hole on the inside was not being blocked by making the hole bigger inside. Here the golf tee is seen and hopefully there will be enough clearance for the next vaporization to enter the hive unobstructed.
 

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Residue will form if there's a solid surface around the output of the nozzel.

Drill a new hole in a location you can be certain there will be no solid objects.
You are absolutely right. I had a cap blow off my Provap 110 because the nozzle was too close to the ipm frame support and other solid structures in my base. The molten OA builds up, solidifies and only bad stuff happens, but most important, the cloud of OA isnt being delivered into the hive......

I went in today and painstakingly inspected the ingress hole for each hive and made those openings larger. Luckily i have a screened access panel used for ventilation that I had to remove to access the inside.....i blocked the front entrance, but they were all clustered anyway...
 

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My second year using OAV and although using Johno's device,the output tube is pretty much the same.My application holes are 1/4 in dia. and drilled in the upper edge of the bottom board on the north side.Even though I plugged each hole with a golf tee,I checked each hole before application by inerting a small phillips screw driver at least 3 in.A small number were plugged with propolis.20 seconds is a small price to pay to protect my one good eye.
 

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I think another problem is that to get the nozzle into the hive opening I have to raise the back up, which angles the nozzle at the bottom board. I need to put a bend in the nozzle. I will give these a try this evening.
This is a problem I had on a few hives after I first started using using Johno's Pro Vap. The problem was that some of the holes I drilled were angled sightly down causing the vapor to contact the BB. The holes were also a tight fit not allowing the vaporiser to hang down slightly. All I had to do was correct this and it has been smooth sailing since.

Alex
 

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This is a problem I had on a few hives after I first started using using Johno's Pro Vap. The problem was that some of the holes I drilled were angled sightly down causing the vapor to contact the BB. The holes were also a tight fit not allowing the vaporiser to hang down slightly. All I had to do was correct this and it has been smooth sailing since.

Alex
The outlet of the vaporizer needs to be clear below to alow any condensed water and OA to fall free from the tip, if it cannot fall free it will just back up into the nozzle and block it. It has also been shown that all OA is not equal. Some users have had problems when using other brands and the problem disapears when they return to Florida Lab's Oxalic acid. I have used the OA supplied by Florida Labs for around 7 years now and have used it while developing the vaporizers I made without any plugging problems provided that propolis wax or condesed water and OA block the tube through fault of my own. As I use a propane torch for lighting my smoker I also use it to clear any propolis or wax blockages when they seldom occur.
 

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The hot OA vapor will transform to crystals much, much, quicker when contacting any solid material than when meeting only air. It must give off energy to effect the change of state and does so by raising the temperature of what it contacts. Air has very little mass; 0.0807 lbs per cubic foot to be exact while wood is around 50 lb. per cubic foot and metal 400 lbs or more. Solids suck the change of state energy out far more effectively.

Contacting air results in formation of micro crystals while contact with denser material results more like snow flakes or icicles. Once the micro crystallization occurs the plume acts like smoke and will flow throughout the frames without glomming on in layers. Dont engineer your vaporizer stream so it impinges immediately on solid material or much of your charge will stick to it like the proverbial sh_t to an old grey blanket!
 
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