Common sense and precautions of low temperature Dewar tank (bottle)
one oxygen storage capacity of a 175 l Dewar bottle is equivalent to that of 28 40 l high-pressure cylinders, which greatly reduces the transportation pressure and reduces the capital investment.
Function

The main structure and functions of dewars are as follows:

① Outer cylinder: in addition to protecting the inner barrel, it also forms a vacuum interlayer with the inner barrel to prevent the invasion of heat outside the bottle and reduce the natural vaporization of cryogenic liquid in the bottle;
② Inner cylinder: Reserve low temperature liquid;
③ Vaporizer: through the heat exchange with the inner wall of the outer barrel, the liquid gas in the bottle can be transformed into the gaseous state;
④ Liquid valve: control Dewar bottle to fill or discharge liquid from the bottle;
⑤ Safety valve: when the pressure of the vessel is greater than the maximum working pressure, the pressure will be released automatically, and the take-off pressure is slightly greater than the maximum working pressure;
⑥ Discharge valve: when the Dewar bottle is filled with liquid, this valve is used to discharge the gas in the gas phase space in the bottle, so as to reduce the pressure in the bottle, so as to fill the liquid quickly and smoothly.

The other function is that when the pressure in the Dewar bottle exceeds the maximum working pressure during storage or other conditions, the valve can be used to manually discharge the gas in the bottle to reduce the pressure in the bottle;

⑦ Pressure gauge: indicating the pressure of the inner cylinder of the bottle;
⑧ Booster valve: after the valve is opened, the liquid in the bottle will exchange heat with the outer cylinder wall through the supercharging coil, vaporize into gas, and enter the gas phase space on the upper part of the inner cylinder wall, so as to establish a certain driving pressure (internal pressure) of the cylinder, so as to drive the low-temperature liquid in the bottle to flow;
⑨ Use valve: it is used to open the pipeline channel between Dewar liquid vaporization circuit and user gas inlet end, and it can also be used to control gas flow rate;
⑩ Liquid level gauge: it can directly indicate the liquid level in the container, and the installation position should be convenient for the operator to observe and repair.

Manufacture

According to the structural characteristics, the production of inner and outer layer cylinders of insulated bottles is divided into two logistics lines, which are summarized to the public logistics line during assembly. The basic model is as follows:

Inner cylinder

Head (external customized) inspection — head nozzle assembly welding (manual argon arc welding station) — delivery to the position of cylinder body assembly (material trolley) — Inspection of sizing plate (external processing or self-processing) — coiling (3-axis plate rolling machine, with small curling linear segment) — conveying to longitudinal seam welding station (material trolley) — longitudinal seam automatic welding (TIG, MIG or plasma welding process, according to the cylinder body specification and The wall thickness is fixed) – it is transported to the welding station with the head (material trolley) – automatic girth welding (locking crimping and inserting, MIG welding) — conveying the cylinder body (roller table platform) from the opposite side of the operator — cleaning and pressing inspection — placing it on the turning car — wrapping the insulation layer (special insulation winding tooling) — assembling with the outer cylinder (vertical and external on the hoisting station of winding machine) Barrel assembly)

Outer cylinder

Length plate (external processing or self-processing) inspection — rolling circle (3-axis plate rolling machine, with small curling straight section) — conveying to longitudinal seam welding station (material trolley) — longitudinal seam automatic welding (TIG, MIG or plasma welding process, determined according to cylinder specification and wall thickness) — conveying to the station for assembly welding with head (material trolley) — automatic circumferential welding (locking crimping insertion, MIG welding) — from operation The author finished the welding of opposite conveying cylinder (roller table platform) – cooling coil of inner wall welding drum (gas welding) — put it on the turning car — and assemble with the inner cylinder (vertical to the outer cylinder body on the hoisting station of winding machine)

Finished products of inner and outer cylinders

The assembled workpiece is installed with outer head – automatic girth welding (MIG welding) – placed on the turning over trolley – translating the workpiece to the horizontal conveyor belt – welding the external fastener and handle of the cylinder head (manual argon arc welding) – Leak Detector inspection

Packing and warehousing

For large cryogenic vessels, the logistics line and longitudinal girth welding are basically produced in the same line, and the logistics transport trolley, longitudinal girth welding, automatic welding of copper cooling coil on the inner wall of the outer cylinder, barrel polishing and inspection, etc., are determined according to the actual production situation. Generally, the process is as follows:

Customized sheet metal inspection — moving to the rolling station — hoisting the vacuum sucker to the feeding section — feeding and rolling — removing the cylinder body — longitudinal seam welding (using plasma or MIG welding) — moving out of the longitudinal seam station (the inner cylinder is covered with thermal insulation winding film, and the outer cylinder is automatically welded with copper cooling coil) — head assembly — girth welding — completion of inner and outer cylinder assembly welding — outer wall polishing in closed polishing room — inspection Leakage inspection – packaging and warehousing.

security

Generally speaking, Dewar bottle has four valves, namely liquid use valve, gas use valve, vent valve and booster valve. In addition, there are gas pressure gauge and liquid level gauge. The Dewar bottle is not only provided with a safety valve, but also with a bursting disc [6]. Once the pressure of the gas in the cylinder exceeds the trip pressure of the safety valve, the safety valve will immediately jump and automatically exhaust and relieve pressure. If the safety valve fails or the cylinder is damaged by accident, the pressure in the cylinder rises sharply to a certain degree, the explosion-proof plate set will break automatically, and the pressure in the cylinder will be reduced to atmospheric pressure in time. Dewar bottles store medical liquid oxygen, which greatly increases the oxygen storage capacity.

There are two ways to use Dewar bottles

(1) Dewar bottle gas use valve: connect one end of the high-pressure metal hose to the Dewar bottle gas use valve and the other end to the manifold. Open the increase valve first, and then slowly open the gas use valve, which can be used. Most hospitals only use gas phase valve to meet the gas requirements.
(2) Dewar bottle liquid use valve, using high-pressure metal hose to connect the Dewar bottle liquid valve pipeline with the vaporizer, the size of the vaporizer is configured according to the gas consumption, the seamless steel pipe is used to transport gas, and the pressure relief valve, safety valve and pressure gauge are installed on the pipeline to control the safety of the gas supply system, which can not only facilitate and stabilize the use of gas, but also ensure safe use. When using Dewar bottle, make sure that the connection is good, and then open the liquid use valve. If the gas pressure can not meet the use requirements, open the booster valve, wait a few minutes, the pressure will rise and meet the use requirements.