Keywords

Withdrawal equipment includes devices to draw LN from a container or dewar. Less sophisticated devices include dippers, long thin steel rods with a steel cup at the bottom end to immerse into the dewar and obtain small quantities of LN. More sophisticated devices include faucets with a switch and a filter. They come in sizes that depend on the amount of LN the dewar can store.

Accessories range from withdrawal stands that allow pouring LN from larger dewars to filters that clean the LN, replaceable caps with cores, pouring spouts, etc. A measuring rod is a helpful device that indicates the level of LN still in the dewar.

Smaller dewars can be carefully tilted by hand to allow pouring, but larger dewars require stands that can tilt or devices with which to withdraw. Several types of withdrawal devices are on the market; some have stems that reach deep into the container while the outer portion (resembling a lid), has a spout; increased pressure within the container due to the expansion of LN, or manually introduced via a pump, propels the LN from the container through the spout. These devices vary according to sophistication (i.e. incorporating a safety valve and pressure gauge on the device itself), how they attach to the dewar, flow rate through the spout, and necessity to warm up in between uses. Examples of withdrawal devices are shown below.

Fig. 11.1
figure 1

Withdrawal device for dewars of 20 l and over. (Brymill™): Conveniently fills multiple delivery units at a time. Affixes to the top of the dewar (i.e., is not removed after each use), has a simple on/off switch, and works like a faucet. Includes a filter that helps clean the LN before it is withdrawn

Full size image
Fig. 11.2
figure 2

Withdrawal tube for dewars of 5–20 l. (Brymill™): Simple and efficient way to extract LN from a storage dewar. Fills one to a few delivery units at a time. The tube is removed from the dewar after each use. Offers quick pressurization. Includes a filter that helps clean the LN before it is withdrawn

Full size image
Fig. 11.3
figure 3

Filters for withdrawal devices. (Brymill™)

Full size image
Fig. 11.4
figure 4

On the left: Dipper for 10LD, LD10, or any 2 in. throat dewar (1 1/4 oz). On the right: Dipper for 25LD, LD25, 35LD, LD35, or any 2 1/2 in. throat dewar (2 oz). Rigid dippers are also available for the MVE5, MVE10, MVE20 and MVE50

Full size image
Fig. 11.5
figure 5

Dippers rigid and swivel small for MVE® Dewars: 5, 10, 20, 30 and 50 l

Full size image
FormalPara Dewar Caps and Cores
Fig. 11.6
figure 6

Replacement cap for 4LD and LD4 T&W, 5LD and LD5 T&W, 10LD and LD10 T&W, 25LD and LD25 T&W, 35LD, LD35, 50LD and LD50 T&W dewars

Full size image
FormalPara MVE® Replacement Caps and Cores
Fig. 11.7
figure 7

On the left: replacement cap and core for MVE4, MVE5, MVE10, and MVE20. On the right: replacement cap and core for the MVE30 and MVE5o

Full size image
FormalPara Measuring Rods

Low conducting plastic measuring rods clearly show LN level in a dewar (in inches and centimeters). 42″ long.

Fig. 11.8
figure 8

Measuring rod for all size dewars DO-31

Full size image
FormalPara Pouring Spouts
Fig. 11.9
figure 9

Pouring spout MVE5/PS for MVE5 and MVE10, MVE20/PS for MVE20, and MVE30/PS for MVE30 and MVE50 (MVE®)

Full size image