If you buy a used one, or the one from Biobase China make a quality
check before. Loosing crystals during shipment means loosing money
(accounting for all the efforts that went in producing the crystals).
I once got a protocol from Terese Bergfors at Uppsala University". It
consists of what Taylor Wharton recommends (posted on diamond webpage),
but some parts can't be found on their webpage.
*Care of dry shippers***updated July 2015/tex**
*Good Practices*
For optimal transportation of your crystals it is imperative that you
look after your dry shipping dewars. Here are some tips on how to make
sure that you don't lose your crystals or introduce ice onto your pucks
and pins.
*Handling and loading*
·Handle with care. Sudden impact can damage the dewar: please ship your
dewars in the appropriate shipping container.
·Be careful when placing heavy items (puck holders for example) in the
dewar. Do not drop them in, since this could damage the neck of the dewar.
·Do not pack items that are too tall for the dewar, nor incorrectly
install its lid to make the items fit. Forcing the lid down can damage
the neck.
*Charging with liquid nitrogen*
·Charge the dewar as recommended in the manufacturer's instructions
(photocopy these and tape to the side of the dewar if necessary).
·Minimise liquid nitrogen spillage on the vacuum release valve near the
top of the dewar.
·Check that the 'charged' dewar weight is in line with manufacturer's
recommendations E.g., in the case of the Taylor Wharton *CX-100* dry
shipper dewar, it will weigh 3.6kg more than the 'dry' weight, and thus
provide enough absorbed liquid nitrogen to keep the dewar at liquid
nitrogen temperatures for 22days (16 days for the *CXR-100; *see
overleaf for details*),* and only when brand new, and provided the
vacuum has not been compromised.
·How do I check the dewar holds its charge? Do a NER (normal evaporation
rate) test:
oRecord the tare weight (= the empty dewar plus its lid).
oProperly charge the dewar as per manufacturer's instructions, i.e. fill
with liquid nitrogen and leave the dewar for 2-3 hours.
oExcessive accumulation of condensation or ice indicates damage.
oPour off the excess LN2. Record the drained weight = charged weight.
Should be ≈3.6 kg more than the dry weight. Per the specs of a new
CXR100, the absorbed amount of LN2 is approx. 3.7 liters of LN2. Once
you see that number start going down, it is time to change the socks
(usually every 3 years).
oAfter 24 hours, weigh it.
oRepeat again after 24 hours=48 hours total.
oThe maximum acceptable NER (normal evaporation rate) is 0.14 kg per 24
hours.
·Check the dewar every time you use it (or at least every 3 months).
*Drying*
·Ensure the dewar is dried between uses. Residual moisture can cause
damage to the foam material if frozen in situ.
·How do I speed up drying? What is the most effective procedure?
oPurge with dry nitrogen or air.
oLeave in a dehumidified room.
oIt is okay to use a boot drier (e-mail correspondence with
Taylor-Wharton 2015.07/tex)
oBe careful: it may still take several days to fully dry.
·How do I know if it is dry?
oWeigh the dewar at time of purchase (record this on the dewar).
oWhen dry, the dewar should be within 0.5kg of the original dry weight.
oWeigh during drying until it no longer decreases.
·If you don't have time to dry the dewar properly between visits to
synchrotrons, we strongly advise you to purchase more shipping dewars.
A well cared for dewar that is properly charged with liquid nitrogen
before use should keep crystals safe for at least a week without
refilling being required.
*What is the difference between CX100 and CXR-100?*
1. CXR100 vs. CX100
They are the same price here, so is one better than the other? The only
difference I see is that one has a sock and one does not. Does the sock
make the CXR100 a better dewar? (Better=holds temperature longer). No –
Both units have socks inside of them. The CXR model allows you to
replace the socks over time. The CX model the absorbent sock is
permanently built into the unit, you can’t replace it. The costs are the
same but the performance is different. There is a tradeoff – if you want
the ability to change out the socks you go with the CXR model but the
performance of the unit is different compared to the CX model. The
Static Holding Time for the CX100 is 22 days for the CXR100 is 16 days.
The CXR has a removable sleeve in the holding cavity that keeps the
socks in place. That removable sleeve is made of a hardened plastic.
This sleeve introduces more direct heat into the cavity of the unit thus
having a shorter Static Holding Time.
2. What is Static Holding Time? Static Holding Time is a value we use to
judge the performance of a unit. The value is made up of the amount of
LN2 in liters divided by the NER performance. This will give you the
number of days or length of time a unit can hold product until it
