Duval flask filling procedure

1. Check that there is no grease around, and that the bottle mouth, pipes, and tools are free of grease. Prepare copper connectors, special tools, and low-temperature gloves. 2. Check that the Dewar flask has no visible damage, that all attachments are in good condition, that the nameplate is clear, and that the pressure gauge and volume indicator are accurate; also verify that all valves and connections are in good condition. 3. Weigh it or place it directly on a scale and note the weight of the empty bottle. 4. Locate the Dewar fill port, which is generally located opposite the Dewar vent valve. Ensure the interface is free of water to prevent condensation at the interface. Use a copper connector to connect to the Dewar inlet and interface it with the filling hose. 5. Verify that the filling valve is closed, the Dewar inlet valve is closed, and the vent valve located between the filling valve and the Dewar inlet valve is open. 6. Clean the pipeline. Open the tank valve; if the pressure in the tank is insufficient, increase it appropriately. (At this point, ensure that the Dewar valve is closed, close the vent valve, and open the filling valve to allow oxygen to fill the pipelines and hoses.) Close the filling valve and open the vent valve to release any residual oxygen in the pipeline. Ensure the pipeline is at positive pressure at the time of release. ) If the oxygen purity is very high, the process inside the parentheses is performed 15 times. After cleaning, close the vent valve. 7. Begin filling by opening the filling valve, as well as the Dewar inlet valve and the Dewar vent valve. Ensure that the pressure inside the bottle is lower than that of the tank before starting to fill it with liquid. 8. To determine that filling is complete, a: if filling is done on a scale, the weight of the liquid reaches the weight indicated on the nameplate. b. Drainage through the Dewar vent valve. c, the capacity indicator shows it is full. Meeting any of the above criteria can be considered as being full. Record the filling weight. 9. Close the Dewar inlet valve and the Dewar vent valve, as well as the pipeline filling valve. If no further filling is required, the tank valve can be closed; if the tank is under pressure, close the tank pressure relief valve. Open the pipeline filling valve and the pipeline vent valve to drain the liquid from the pipeline. 10. After draining the liquid and pressure from the pipeline, the hose can be removed. 11. Clean the area, put away the tools, and print the receipt.

Thank you! ! ! I’d like to ask again, what is the typical filling pressure?

This post was last edited by springflower on 2012-6-5 at 14:24. It depends on the pressure in the tank; venting the Dewar during filling ensures a sufficient pressure difference between the Dewar and the tank, which speeds up the filling process. Basically, the vent valve of the Dewar remains open throughout the filling process (the pressure in the Dewar tank is probably around 2–3 bar). Some companies, in an effort to save energy, wait until pressure rises (to levels of 4–6 bar) before activating the Dewar vent valve, which results in a very slow filling process. As a result of the long filling time, the liquid in the pipelines vaporizes into gas, leading to even more venting.

Our storage tanks are flat-bottomed tanks, with a pressure of only 5/6 kPa; however, we have a filling pump that can achieve a pressure of 0.5 MPA； I now want to take a sample from behind the pump to fill the Dewar flask; I’m not sure if this is possible If it’s possible, what are the risks, and how can they be avoided?

Our storage tanks are flat-bottomed tanks, with a pressure of only 5/6 kPa; however, we have a filling pump that can achieve a pressure of 0.5 MPA； I now want to take a sample from behind the pump to fill the Dewar flask; I’m not sure if this is possible If it’s possible, what are the risks, and how can they be avoided?

In that case, a cold pump and a cold tube purging process are required; the filling valve is used to discharge the liquid. However, the pressure is relatively low, so you need to keep the Dewar’s vent valve open, which may result in a slower filling process. Using a pump may contaminate liquid oxygen, of course this applies to oxygen of 6 nines in terms of purity; for oxygen with a purity of 99.9%, this issue can be ignored. However, the pumps we use are for loading tank trucks, with oxygen of 99.5% purity.

Our oxygen purity is over 99.5%, but there is still a risk due to potential contamination； So, before starting the pump to fill it, what pressure should be reduced in the Dewar vessel? Or, to put it another way, to what minimum level can the pressure in a Dewar flask be reduced?

How do you load and transport your Dewar flasks? It’s very troublesome for us with trucks (to load them) every time.