Differential pressure filling system and method for a dosing vessel

1. A dosing vessel comprising:

a. a reservoir having an inlet and a liquid outlet, said reservoir configured to contain a supply of a cryogenic liquid with a headspace above;

b. a dosing arm having a dosing head, said dosing arm connected to and in fluid communication with the liquid outlet;

c. a low pressure sensor configured to detect a vapor pressure in the headspace of the reservoir;

d. a high pressure sensor configured to detect a pressure in a bottom portion of the reservoir;

e. an inlet valve in fluid communication with the inlet of the reservoir and configured to be placed in communication with a source of cryogenic liquid;

f. a controller in communication with the high and low pressure sensors and the inlet valve, said controller configured to store a preset liquid level height or a preset differential pressure corresponding to the preset liquid level height and to determine a measured liquid level height using a measured differential pressure based on data from the high and low pressure sensors and to control the inlet valve based on the measured liquid level height and the preset liquid level height or the preset differential pressure so that a liquid level of a cryogenic liquid stored in the reservoir is generally maintained at the preset liquid level while the cryogenic liquid exits the reservoir through the liquid outlet and is dispensed through the dosing head thereby providing a generally constant dispensing pressure at the dosing head;

g. an outer shell having a cylindrical side wall, a top cap and bottom end plate, said reservoir positioned within the outer shell with an insulation space defined between the reservoir and the outer shell, said space generally evacuated of air so as to provide the reservoir with vacuum insulation;

f. said low pressure sensor including a low pressure phase line having a first end in fluid communication with the headspace of the reservoir and the high pressure sensor includes a high pressure phase line having a first end in fluid communication with the bottom portion of the reservoir, each of said low and high pressure lines terminating in a second end that is fastened to and in fluid communication with a transducer that is in communication with the controller; and

g. a majority portion of each of said low pressure phase line and said high pressure phase line being entirely positioned within the insulation space.

2. The dosing vessel of claim 1 wherein the controller is configured to open the inlet valve when the measured liquid level height is below the preset liquid level height.

3. The dosing vessel of claim 1 wherein the controller is configured to compare the measured differential pressure with the preset differential pressure and to open the inlet valve when the measured differential pressure is below the preset differential pressure.

4. The dosing vessel of claim 1 further comprising a vent tube having a first end in fluid communication with the head space and a bottom end in fluid communication with ambient air.

5. The dosing vessel of claim 4 wherein a bottom portion of the vent tube passes through a bottom of the reservoir and a bottom of the shell.

6. The dosing vessel of claim 4 wherein at least a portion of the vent tube is provided with a jacket so that an annular space is defined between the vent tube and the jacket, with said annular space generally evacuated of air.

7. The dosing vessel of claim 1 wherein each of said low and high pressure lines are in fluid communication with a single shared transducer that is in communication with the controller.

8. The dosing vessel of claim 1 wherein the low pressure phase line is in fluid communication with a low pressure transducer and the high pressure phase line is in fluid communication with a high pressure transducer, wherein each the low and high pressure transducers are in communication with the controller.

9. The dosing vessel of claim 1 wherein the inlet valve includes a needle valve member operably connected to an inlet valve actuator, where the inlet valve actuator is in communication with the controller.

10. The dosing vessel of claim 1 wherein the low and high pressure phase lines are each positioned entirely within the insulation space.

11. The dosing vessel of claim 10 wherein the low and high pressure sensors are each mounted to the bottom end plate of the outer shell.

12. The dosing vessel of claim 1 further comprising a fill tube in fluid communication with the inlet valve, said fill tube having a fill outlet and positioned within the reservoir so that the fill outlet is positioned closer to the bottom end plate than the first end of the low pressure phase line.

13. The dosing vessel of claim 1 further comprising

h. a fill housing containing a fill chamber,

i. a liquid line extending from the inlet valve to the fill housing and configured so that cryogenic liquid flows from the inlet valve into the fill chamber when the inlet valve is open;

j. a fill tube in fluid communication with the fill chamber, said fill tube having a fill outlet and positioned within the reservoir so that the fill outlet is positioned closer to the bottom end plate than the first end of the low pressure phase line.