Welcome, Guest

Author Topic: VOA - a different approach.  (Read 101 times)

Offline little john

  • Super Bee
  • *****
  • Posts: 1514
VOA - a different approach.
« on: November 12, 2020, 02:09:19 pm »

As the traffic is a tad light at the moment, I thought I'd keep you guys up to speed on one of several developments I'm currently working on ...

I'm an enthusiast of Vapourised Oxalic Acid for keeping Varroa mites in check, and for those who are new to this - the principle is very simple: Oxalic Acid Dihydrate is heated until it sublimes (i.e. passes directly from the solid phase to the gaseous phase, without becoming liquid in-between) and, as a gas the molecules begin to spread further apart from each other. Then, having left the heat of the vapouriser, those molecules cool down and so become solid again - but - as they are now spread-out so far apart, what results is an aerosol of fine micro-crystalline DUST (and not vapour). And it is this Oxalic Acid dust which proceeds to reek havoc upon the Varroa mite, but thankfully has no discernible effect upon the bees.

Ok - so how does one go about vapourising Oxalic Acid ?  Well, there are numerous devices on the market, ranging from the 'Varrox' (the original applicator, ideal for the hobbyist, which runs from a 12 volt lead-acid battery), right up to complex professional multi-dosing systems which require both generators and compressors, and which cost thousands of pounds/dollars.

Perhaps the most cost-effective and efficient vapourisers currently available  are the inverting band-heater vapouriser designs, which are fairly new to the market.  These can dose beehives every couple of minutes, but do cost a few hundred dollars, which is a large outlay for someone with a dozen hives or less. For those people who are handy at DIY however, there is a Build-It-Yourself option available, details of which can be found at: https://www.beesource.com/threads/band-heater-vaporizer.332394/

Although inverting band-heater vapourisers are high performers, they do - like most other hand-held vapourisers - suffer from a couple of undesirable features.  The first of these is that during their use the operator is 'up close and personal' with a very nasty chemical. There shouldn't be any problems if all goes according to plan - but what if something should go wrong ?
Secondly, to stand next to a beehive motionless, holding a piece of equipment in place for two or three minutes may not sound like much of an ordeal, but after several dozen hives ? Suppose you have thirty hives, that's 90 minutes standing there motionless like a dummy - albeit 90 minutes spread out over two hours or more.  Personally, I don't think that's a very good use of a beekeeper's time.

The underlying principle behind every vapouriser design I've yet seen is the same: there is but one vapouriser, and the operator moves from hive to hive, dosing just the one hive at a time. But what happens if a fault with that vapouriser should develop ?

The approach I'm currently adopting is different, in that multiple vapourisers (which are exceedingly cheap to make) are used simultaneously - so that 4 or even 8 vapourisers are inserted into beehives, a button is pressed, at which point the operator becomes free to then walk-away to do something else, and return in half an hour or so to repeat the process with yet another 4 or 8 hives.  No standing about like a dummy, and no standing 'up close and personal' with the equipment while it's being used.

However, do be aware that there's a catch - in that this system may not be suitable for everybody, and in particular is only really suitable for someone who builds their own equipment, as a special base is required. And my next post contains details of such a base.

LJ
A Heretics Guide to Beekeeping - http://heretics-guide.atwebpages.com

Offline little john

  • Super Bee
  • *****
  • Posts: 1514
Re: VOA - a different approach.
« Reply #1 on: November 12, 2020, 02:17:08 pm »
Ok - the vapourisers I'm using are cheap and simple to make, and consist of a short length of steel water-pipe with a base welded-on, around which is clamped a 150W mains-voltage band-heater - and that's it !  Each one should cost less than 5 dollars to make.  The 'control unit' will consist of a simple timer (lots of choice there), and a solid state relay - hardly a major expense.

Because of the height of a band heater, a purpose-made base is required with between three-and-a-half to four inches of clearance.

Here's a bird's-eye view of the basic concept:



Let me talk you through it. The 3-sided structure in light brown is some 4" high and made from pallet stringers (support timbers) and a pallet plank. There are more planks in olive green, making a floor, with those towards the rear separated by popsicle sticks (in dark brown) to give a 2mm gap between them. These gaps are required to provide a means for condensed moisture to exit the hive, and for a modest amount of ventilation - with 3 gaps providing around one and a quarter per cent of that ventilation provided by a fully open Open Mesh Floor (SBB).
All of the above woodwork is glued and screwed together, with the only removable plank being that at the rear (shown in blue), which is held in place by two turnbuckles. Here's what it looks like in reality:



There are two 22mm entrance holes in the front wall, and the ventilation slots were primed beforehand as getting paint in them afterwards would be tricky.

In normal use a Slatted Rack occupies the depth of this Base Unit:



With a rear cover being held in place by two turnbuckles.  There is a third (central) turnbuckle which covers a cable-slot in order to keep the whole assembly bee-tight.



With a standard frame in place, it's bottom-bar is approx. half an inch above the Slatted Rack:



And so finally - here's what all of the above has been about - providing sufficient height so that a mains voltage non-inverting band-heater vapouriser can be inserted below the colony much in the same way as a Varrox would be:



The only piece missing is the 'plate' which - once the rear cover and Slatted Rack have been removed, will be slid over the gaps to seal them, before inserting the pre-loaded vapouriser.

The only outstanding work right now is to construct custom anti-robbing screens for this style of base - which will have entrances to the sides of the screen, rather than at the top as at present.  Then it's just a painting job ...

One down, several dozen to go.   :grin:

LJ
A Heretics Guide to Beekeeping - http://heretics-guide.atwebpages.com

Offline little john

  • Super Bee
  • *****
  • Posts: 1514
Re: VOA - a different approach.
« Reply #2 on: November 13, 2020, 08:35:30 am »
Quickest of updates - have this morning received 3.5kg (7.7 lbs) of Oxalic Acid Dihydrate for ?12.91 (17 USD) from an Ebay seller of bulk chemicals.  I've just checked a sample for sublimation temperature and residue, and it appears perfectly ok. A bargain price which included delivery by courier.
If anyone in the UK wants more info - PM me - as I don't want to advertise on the forum (even though I have no connection with this seller).
'best,
LJ
A Heretics Guide to Beekeeping - http://heretics-guide.atwebpages.com