A downdraught OA vapouriser

[Little John]

On the off-chance that anybody else might be vaguely interested in ways of getting OA vapour into a hive - here's a 'proof of concept' I've just finished working on - which you may possibly find of interest, or then again, maybe not ...

From next year onwards I'll be running banks of nucs with their frames positioned 'cold way', and will need a simple method of getting OA vapour into those colonies. And so I decided to use existing crown board feeder holes for this purpose.

This is what has emerged: nothing more than a block of wood with 2 holes machined into it - one vertical, the other horizontal. The only 'unknown' here was just how big a fan would be required to push the OA vapour downwards into a partly sealed box.

The following shot shows the wooden block with it's small fan perched on top. The larger computer cpu fan and the adapter I had planned to use if necessary, are shown for comparison.

This is the block opened-up, which I hope will show the set-up a little more clearly.

If anyone else is tempted to work with this idea, the only important consideration is that the vapouriser pan should not lie directly in the path of the fan's airflow. Other than that, it appears to be a very straightforward technique to employ.

LJ

 

[farbee]

Ingenious.

What is the heat source John?

 

[Little John]

All my hives have multiple 22mm holes, rather than wide entrance slots, so I needed to make a vapouriser which could fit into a 22mm hole, which proved to be something of a challenge. I chose a diesel pre-heater (ex Ford Escort, I think) for a heat source, which is inserted into a tube inside the pan, and attached a thermocouple to the pan's underside to monitor the temperature.
The pan itself is around 20-30 grams, so the heat-up and cool-down times are very fast indeed.

This shows the vapouriser during construction:

and a close-up of the business end:

LJ

 

[farbee]

Ta John nice set up.

 

[mbc]

Ta John nice set up.

+1, following this with interest.

 

[Hivemaker.]

Good fan and adapter setup, LJ, vapourizing from the top is more effective, especially on any double brood colonies.

 

[Little John]

Thanks for the positive comments - it's always good to know that posts are of interest to somebody and don't just go wandering off into the aether ...

The current situation here is that this particular vapouriser has been through about 50 cycles or so without any problems. The wooden block adapter thingy has been tested just three times over an empty box without showing any problems thus far, and will be used 'for real' during this year's OA dosing which should be any day now.

I'll be making 4 more of these, but need to make a large number of bee boxes first. And I thought retirement was going to be about taking things easy ...

LJ

 

[itma]

Good fan and adapter setup, LJ, vapourizing from the top is more effective, especially on any double brood colonies.

How is that normally done? (New to me )

I'd wonder whether, this way, the Oxalic would be well spread through the hive, or concentrated below the fan and hole.

 

[Hivemaker.]

How is that normally done? (New to me )

All our top boards have a small (6mm) hole in the side to insert the vapourizer nozzle. There are various other methods, from a upturned dish to an entire custom made top eke, some even made with perspex windows.

 

[alanf]

Couple of potential hazards to beware of. One is blowing hot oxalic directly into a cluster just under the feed hole. Another is that a pressurised hazardous substance leaves a lot more to think about than an upressurised convection inside the box. With something like a varrox you get gentle drift of a small proportion of the dose from gaps and you can be several metres from the hive during the heating. With a pressurised device you're probably standing over the device and there's always a risk of accidentally directing vapour into your face; that's at least a higher level of ppe.

 

[Little John]

Couple of potential hazards to beware of. One is blowing hot oxalic directly into a cluster just under the feed hole. Another is that a pressurised hazardous substance leaves a lot more to think about than an upressurised convection inside the box. With something like a varrox you get gentle drift of a small proportion of the dose from gaps and you can be several metres from the hive during the heating. With a pressurised device you're probably standing over the device and there's always a risk of accidentally directing vapour into your face; that's at least a higher level of ppe.

One - it ain't hot. Within a few mm of the pan the vapour reverts to micro-fine crystals and then it meets a current of air which cools that 'dust' further. The very first thing I did when conducting trials was to put my hand over the outlet - just a token warmth. If it had been anything more than that, don't you think I would have simply increased the applicator tube length (i.e. made a taller block) in order to cool the vapour further ?
Any bees within a few centimetres of a Varrox experience exactly the same. Commercial 'blower' vapourisers likewise.

Two - a pressurised hazardous substance ? - what pressure is that then ? It uses a circulatory fan (and a tiny one at that), which simply moves air around at atmospheric pressure. The whole system (beehive an' all) is open to the atmosphere - therefore it stays at atmospheric pressure.
To be excruciatingly pedantic, of course there will be a very slight difference in pressure, but you'd be hard-pushed to measure it. I can blow a lot harder than that fan can push air ...

Three - standing over the device. Where on earth did that absurd idea come from ?
One of the reasons I favour electrical heating over the use of a blowlamp with OA in a copper tube (for example), is the proximity issue. I use OA evaporators quite comfortably, always positioned upwind approx. 1 metre away, and without any protection whatsoever - for when used like this, there's really no need for any.

By all means let's have some criticism - that's always a good thing, whether it's positive or negative - but let's not over-egg the pudding in the process ...

LJ


If we want to generate scare-stories - let's talk about the Varrox evaporator, which has no temperature control whatsoever. My system has temperature monitoring and is never allowed to exceed 180 deg C., whereas the Varrox can easily reach temperatures of well over 200 degs C.

Now the flashpoint of beeswax is considered to be around 204 °C - what would happen if a piece of beeswax broke away and landed in the Varrox pan, at just the wrong moment ?

Why does the Varrox not have temperature monitoring or any control over it's temperature ? Why does it not have an over-temperature cut-out device fitted so that it can never reach the flashpoint of beeswax ?

 

[Erichalfbee]

+1, following this with interest.

Me too.

 

[Little John]

Update: First run 'for real' this afternoon. Had planned to dose half the apiary using hive entrances and the other half via feeder holes, but the feeder hole method proved to be so convenient, that I did the whole lot that way.

No problem with full penetration - vapour was seen coming out of OMFs where the sealing was poor, as well as the usual inter-box gaps etc.

For a first run with a Mk.I - very pleased. There was a small amount of frosting directly above the pan - with hindsight this is undoubtedly due to air flow eddy currents holding some vapour back, and allowing frosting to build up there.

I think development of a Mk.II is justified - I'll give it some thought.

LJ

 

[alanf]

...For a first run with a Mk.I - very pleased....

Good, there's a lot of thought gone on. No offence intended before, just pointing out the commercially available devices (varrox, sublimox etc) have been through a lot of field testing, any radical departure from that needs some development and glad you're sharing experiences.

You're right about the overheating potential of the varrox design. A correx sheet wedged up close to an omf can have the surface melting. What the design has got is a relatively simple clean and reset: dipping in a bucket of water starts each run from cold. The sublimox dumps crystal on the constantly hot element as far as I read it. Are you relying on time and air flow for cooling between doses?

 

[wessexmario]

I like the idea, I have a box of noisy but otherwise working computer fans somewhere, and they're 12 volt, same as the vaporiser.

My only thought is that we apply oxalic vapour during the coldest part of the year. Do we really need to blow cold air into the hive? Is the natural circulation from a top application not enough? What sort of temperature drop does this make to the cluster during a typical 2 minute application?

I would have thought that when applying the vapour from the top of the hive that once the vapour condenses back into dust, then gravity would do the work.
While the fan idea is ingenious, is it just over-engineering what works anyway?

 

[yeogi75]

looking at this idea with interest as would work brilliantly on polys no burning the floors

 

[Little John]

My only thought is that we apply oxalic vapour during the coldest part of the year. Do we really need to blow cold air into the hive? Is the natural circulation from a top application not enough? What sort of temperature drop does this make to the cluster during a typical 2 minute application?

Re: cold air blowing into the hive. That is a good point. I wonder how such heat loss compares with opening the hive to trickle with OA over a much longer period ? Can't compare this myself, as I've never trickled ...

I chose a warm day - Xmas Eve - 11 deg C in this locale to dose my girls - so not too traumatic (one hopes).

To keep the draught time to a minimum, what I have been doing is:
Unseal the feed hole, and then slide a stiff clear plastic sheet over it. (This is my normal procedure when installing inverted jars containing syrup or fondant over the feed holes).
Then, place the wooden block (sans fan) over the feed hole, and peer down to check that the holes line up. Then install the fan and connect it, before inserting the loaded OA evaporator and connecting it to the battery.

When the indicated temperature reaches about 80 deg C., I then slide out the plastic sheet, retire to a safe distance upwind, and wait for the temperature to rise to 180 deg C., at which time the evaporator is disconnected.
When the indicated temperature has dropped to below 170 deg C., the plastic sheet is re-inserted and the wood block assembly removed. The fan thus only moves air into the hive for around 20 seconds.

What I did notice on several occasions is that unsealing the feed hole caused a dozen or so bees to investigate, and these could be seen through the clear plastic sheet, milling around on the top bars. When removing the wooden block, a very similar number of bees could be seen still present on the top bars directly under the feed hole. Whether these were the same bees or not - who knows ? - but they didn't seem at all phased by the procedure.

I've never seen a passive top application of OA vapour through a relatively small Crown Board hole 'first-hand' - but if it has been proven to work, then I'll certainly try it for myself.
The advantage of a fan - as I see it - is that the OA is pretty-much guaranteed to be circulated by the gentle air currents it creates.

But - that's not to say that I'm wedded to this method - all I'm trying to produce is a cheap, quick, and effective method of dosing with OA vapour using any of the existing holes in my boxes - which are 4 x 22mm entrance holes, and 4 x 50mm Crown Board feeder holes in full-sized hives, and 2 of each of those in nucs.

There's always dosing through the OMF of course, but so far I haven't considered that route of entry.

'best
LJ

 

[SixFooter]

I could use something like this only to blow in a straight line through the entrance of a nuc. Most of my nucs have solid floors and my varrox won't fit through the entrance. Do the pre heaters all have the same characteristics?

 

[Little John]

I could use something like this only to blow in a straight line through the entrance of a nuc. Most of my nucs have solid floors and my varrox won't fit through the entrance. Do the pre heaters all have the same characteristics?

Most I've come across are rated for 11 volts - which ensures that they still glow nicely when connected to a poorly charged vehicle battery. I'm sure they also come in a 24 volt flavour for commercial vehicles - but let's not go there ...

The big difference I've noticed is their length - that can vary considerably. I bought a set of 4 long-reach Land Rover glow-plugs on Ebay a while back for a fiver - the hot tip being 3.5" away from the securing threads - my thinking being that the extra distance would prevent the rest of the kit getting too warm during multiple doses - but - haven't worked on any design for those yet.

A vapouriser with the 'T' shape of a gun might be the way to go - with the vapouriser in the handle, and a fan on the back, blowing air across the top of the pan and into the 'barrel' nozzle. That would certainly work. My only reservation with that type of design is operator proximity - personally, I do like to be a metre away when the stuff becomes airborne.

LJ

 

[wessexmario]

I did mine today...
Yesterday I had originally tried to modify a coverboard (one with a feeder hole that I no longer use) by adding a box for the vaporiser and a PC fan to blow the vapour down from the top of the hive as suggested earlier, but the whole thing was a bit over-engineered and a bit of a phaff trying to keep the vapour contained, I found that the draught from the fan cooled the vaporiser too much. so I abandoned that idea.

Having OMFs, I blocked the entrance and put the vaporiser on a board under the OMF, cracked the seal on the cover board and slid it gently to one side so there was a paper thin gap all along one edge. (I was going to suggest a matchstick but think I'd better not - it might confuse!) The natural convection from the warmth of the vapour let it circulate upwards through the hive and the small seep of white fumes from the crack along the edge of the coverboard confirmed the vapour was reaching all parts without any need for opening the hive up.

Wore a mask but no need for a bee suit, and no disturbance to the bees.

Even without a perfect seal below the OMF, the natural rise of the vapour meant that more came out of the small gap at the coverboard than the much larger gaps around the board supporting the vaporiser under the OMF.
Using natural convection proved for me that K.I.S.S. was the best choice.