The usual enquiry starts at the spec: which size, which hold time, which model. Wrong entry point. The first branch is own or hire, and it resolves on two inputs: shipment frequency and how much control you need over vessel condition.
First, what the device is
A dry shipper holds liquid nitrogen absorbed into a porous inner matrix, not as free liquid. Samples travel in vapour phase. The vessel can be inverted without spilling because there is no free liquid to escape.
That construction drives the regulatory position, which is worth getting right because it is routinely stated wrongly:
- The shipper travels as not restricted under Special Provision A152 of the IATA Dangerous Goods Regulations, provided the packaging cannot build pressure or release nitrogen in any orientation and the air waybill carries the words not restricted together with the special provision number.
- The samples inside are governed by Packing Instruction 650, where they are classified as UN 3373 Category B.
A dry shipper is not exempt from PI 650. PI 650 was never about the nitrogen. These two get conflated constantly, including in supplier literature.
Branch: hire
- Infrequent shipments. A purchased unit used a few times a year sits empty, still consuming storage space, inspection and charging time.
- One off capacity overflow. Needing more than your own unit holds is a hire, not a second purchase.
- Capital constraint. Hire moves cost from capex into the shipment, which is easier to approve and easier to recharge to whoever the shipment is for.
- Peak cover. Regular baseline plus occasional surges: hire the surge, do not own the peak.
Branch: own
- Frequency. The crossover sits lower than expected once staff handling time is counted properly.
- Control, the stronger argument. You know your own vessel's history, whether it has been dropped, how it performed last time. A hired unit puts you inside somebody else's inspection regime, and a shipper that has taken a knock can carry a degrading vacuum with no external sign at all.
- Readiness. Charging is not instant. Owning means preparing on your timetable, which matters when a transfer date moves.
Hold time: read it as a ceiling
Published figures are measured upright, unopened, at moderate ambient. Real shipments break all three: orientation changes, ambient varies, customs holds happen, and every opening costs hold time that is not recoverable.
Treat the published number as an upper bound under ideal conditions and size the margin against the delay you have not planned for. A hold time quoted without its measurement conditions is not a planning input.
Charging: the actual failure mode
Undercharging is the most common cause of a failed cryogenic transport, and it is entirely preventable.
- Saturate the matrix fully. This takes appreciably longer than most protocols allow.
- Invert and drain so no free liquid remains. Skipping this leaves free nitrogen in the vessel, changing both its regulatory position and its behaviour in transit.
- Weigh before and after, and record both. Weight is the only practical measure of cold mass actually in the vessel, and the only check that catches a matrix that has not taken a full charge.
Safety note worth building into the procedure: BCGA Code of Practice 30 records that asphyxia due to oxygen deficiency is often rapid with no prior warning to the victim. A freshly charged shipper does not share a lift with a person.
Full article: Dry Shipper Hire or Purchase
Top comments (0)