We have stopped breeding Hanoverians for a couple of years, but when we start up again I will be using frozen semen and doing it myself. I have recently come across a used semen storage tank and I am wondering if it would suit my purposes. Can tanks sit unused for a couple of years without losing any of their usefulness? The tank is an MVE SC 33/32 and is about 10 years old. It has had one owner and they say it is still in excellent condition. I will have to purchase sight unseen so are there any questions that I should be asking them?
Nitrogen tanks are a big vacuum flask. As long as the vacuum is intact, all is fine - the vacuum provides the insulation. If the vacuum seal is broken for any reason (damage, wear, etc.) then the vacuum will be lost and the nitrogen will boil off very quickly - literally a matter of hours in some cases. This can happen with any tank, but obviously the risk becomes greater the older the tank.
If you are going to be using a tank for long-term primary storage - especially of a significant number of straws - then for the sake of the savings in buying a used tank vs. a new tank - lost semen vs. OK semen - is probably not worth it.
Are you sure it's a 33/32? I suspect it may be an SC 33/26. This is a good mid-size tank, although it might be a bit more than you require if you are looking at only a few doses of semen and buying a new tank. If that is the case, we recommend the XC MILLENIUM 20 which currently retails for $535 - freight within the US included - from the company linked below (SemenTanks.com), which we have found to be one of the cheapest and best.
Thanks for all the info. It's definitely a 33/32 as I have seen photos of it. How can you tell if the vacuum seal is broken? Can a tank sit in storage not being used for a couple of years without creating any problems? Also, the tank was used to store bovine semen. Will it require any kind of changes/cleaning to make it suitable for equine semen?
You will be able to tell that the vacuum seal is not good if, when you fill it with nitrogen, the outside of the tank frosts up, and the nitrogen contained within boils off rapidly.
A tank can sit unused for years and still be fine, as long as it has been stored correctly - not on concrete or in a position to be damaged (the concrete encourages oxydation of the metal).
Bovine and equine semen tanks are the same thing, so other than the fact that you might want to rinse it out with a chlorine bleach solution if there are any broken straws in the tank (or have been, which you won't know) - making sure you allow it to dry well before filling with nitrogen - there really is nothing else needed.
Unfortunately, there really isn't an answer to your questions! I have tanks that are 20 years old and work well and I have seen tanks that are 5 years old and have failed.
As far as "how often do they need filling", the easiest thing is to point you at this location. As you can see, it will depend upon the size of the tank! The "working duration" is the amount of time that a tank will stay filled (on average) in the event that there is some traffic going in and out of it. One would never let it go that long however, as that is the duration to empty (and even that can vary a little), plus one should always dip tanks on a weekly basis in order to determine if the levels are dropping more rapidly than anticipated, and toe ensure there is adequate LN2 in them.
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