Size the vessel from your inventory, not from the catalogue. And build the projection knowing that discards have slowed to a trickle: since 1 July 2022 UK patients can store for up to 55 years with consent renewed every ten (HFEA), so samples arrive far faster than they leave.
The method
- Count current straws by format: 0.25 ml, 0.5 ml, high security, vitrification devices.
- Add the annual freezing rate for each, minus realistic discards, not hoped for ones.
- Multiply by the years before you would rather buy a second vessel than an oversized first one.
- Convert that into goblet, cane and rack positions for the vessel’s own organisation system.
Where a supplier earns the order
The last step, because rack capacity depends entirely on the goblet and visotube combination you run. Cryolab’s CryoNest® XL, XXL and XXXL sit at 95, 145 and 175 litres with six racks each, which covers most single site clinics.
The variable most people forget
Access frequency. A tank opened twenty times a day loses far more nitrogen than an archive opened weekly, so splitting working stock from long term storage often costs less to run than one large vessel.
The CryoNest® pages list rack and compartment counts per size for the conversion step.
