Parts of a Semen Tank

Click on the photo to see an overview of Semen Tank Construction

Basics of a Semen Tank

Semen Tanks are normally built from aluminum. They consist of 2 tanks, one inside another, with a vacuum between them to maximize insulation. This insulated inside tank holds liquid nitrogen that nataurally expresses into gas when in contact with warm air. The super insulated tank (due to the vacuum barrier) retains the nitrogen longer by keeping the temperatures at a steady -190C degees.

Cryogenically frozen semen, if cared for correctly, can last for an infinite time at the liquid nitrogen temperature of -190C and used decades later to breed succesfully.

Semen Tank Lid

Semen Tank Lid

The Semen Tank lid might seem straight forward but it is extremely important. The hinged lid should cover the tank canister area as completely as possible to keep out dust and water than can be encountered when working in the field.

If water is allowed to get on the cork it will freeze in place and be very difficult, if not impossible, to get out. You will also notice this tank has a recessed lock tab in order to secure the tank. It's a good idea to lock the tab even if not for security reasons since high wind can pop the lid open and suck the cork out of the tank.

Semen Tank Handle

Semen Tank Handle

Semen Tank handles are important because tanks can sometimes be heavy and awkward. They should always be kept level and sat down gently to avoid breaking the fiberglass seal between the two tanks. If that happens, the vacuum will be lost and the liquid nitrogen will express to empty in a few hours or less.

It's important to have handles that fit the hand comfortably without slipping. The easier a tank is to carry, the less chance of dropping it or setting it down too roughly. If your hand fits into the handle and there are no sharp edges, it should be fine. The diameter of the handle should be big enough that your hand can grasp it easily and not so big that you have no grip.

Semen Tank Cork

Semen Tank Cork

Semen Tank corks are designed to fit loosely in the tank neck and allow liquid nitrogen to express as a gas. It might seem that a sealed tank would hold nitrogen better, but the build up of gas would eventually rupture the tank.

It's important to keep the cork dry and clean because if it's wet, it will freeze to the tank neck and be almost impossible to pull without destroying it.

Semen Tank Vacuum

Semen Tank Vacuum

As we have discussed, there are actually two tanks fused together with a fiberglass neck to make a semen tank. The inner tank is the reservoir that actually holds the liquid nitrogen and the outer tank is a protective shell.

Between these two tanks is a vacuum that creates a super insulation capable of protecting the inner tank from heat build up that would express the liquid nitrogen much faster.

If a tank is damaged and begins to loose it's vacuum it will begin to express nitrogen faster and eventually be unusable for storing semen or embryos.

Semen Tank Rib Construction

Semen Tank Rib Construction

Although it might seem the ribs formed in a semen tank are to make it look good rather than just a flat surface. Actually, the ribs on the tank add an incredible amount of strength to the tank walls while keep the weight down. The ribbed walls are engineered from lighter material but the way they are constructed gives them more strength than a much thicker, and heavier material. 

Semen Tank Canisters

Semen Tank Canisters

The canisters are the part that hold the semen cane. Tanks come with different numbers of canisters but the most popular is six per tank.

Canisters are constructed from stainless steel as it holds up better to the extreme cold conditions inside the tank. There is a fiberglass stem that connects it to the handle at the top of the tanks. Fiberglass is used to connect to the top of the tank because stainless would transmit the cold and liquid nitrogen would be lost at a much faster rate.

Most tanks come with a numbered ring to help organize your inventory and keep track of where everything is in the tank. When the canes of semen are placed into the canisiter only the top tabs with cane codes are visible, so it is impossible to tell what is in the canister without the codes. Having a number system makes it easier to find what is needed very quickly.

At the bottom of the semen tank is the spider. It is a small piece with slots that allow the bottom of the canisters to rest against it. This keeps the canisters from rattling when the tank is being moved and helps to keep them in place when removing and replacing them.

AI Shield Canisters

AI Shield Canisters

The AI Shield canister is offered by Worthington as a solution to the loss of semen during handling. The temperataure in the neck of the tank is quite a bit higher than in the main reservoir area, making it an area susceptible to semen loss.

The AI Shield canister helps prevent this issue by using an adsorbent material to hold liquid nitrogen in the canister even as it is pulled into the neck. Not unlike a dry shipper, this canister now has the ability to maintain the cryo temperature much longer than a standard canister when out of the liquid in the tank. Studies have shown very favorable results over the long term and it looks like this technology will be widely available very soon.

The AI Sheild canister and a standard canister are identical in outside diameter but inside it is slightly smaller due to the adsorbent material.

Vapor Shippers

Vapor Shippers

Vapor Shippers or Dry Shippers are used to transport semen and embryos via common shipping companies like UPS or FedEx. The law states that hazardous liquids can't be sent using these carriers so an adsorbent material soaks up the nitrogen in the tank. This makes the tank legal to ship because it is now "dry" and can not be spilled.