delievery truck pump pressure

[tope]

I have an old 600 gallon liquid nitrogen dewar. I'm worried that it is possible for the pump on the truck that fills it to over pressurize the vessel. Its MAWP is 250 psig. BOC has the contract for filling our dewars (tanks), however I have not been able to get a pump curve for one of their trucks from them. They tell me not to worry because the relief valves/rupture discs will protect the vessel. I disagree because the relief devices were sized for fire, not for truck fill rate. A few people had told me that the truck pumps can deliver 200 GPM LN2 at 350 psig? Does anyone have an idea of what these delvery trucks can actually deliver?

 

[rerickson]

I wouldn't worry too much. The standard MAWP for a tank that size is ~220 psig and BOC is filling tanks like that all day long. Most off-loading pumps are good for about 100 psig above the pressure of the tanker, so maybe 120-150 total. Just make sure that you have the Trycock open when filling to make sure the tank isn't overfilled, or then you might have a problem with pressure.

 

[RC19]

It is true that Pressure relief Valves/ rupture disc in the container would handle the pressure rse if abnormal and moreover BOC handles these kinda jobs in Tons and there is no need to worry!!! Whenever a cryo vesses or in your case, a dewar is designed the relief valves are designed to operate at a pressure less by 30% of your MAWP. A rupture disc would operate/ break away at 15% of your MAWP and they will be able to handle all the pressure rise here. I ve been working with Cryo vessels for a long time and had a great deal about it in UG courses too.

Hope this solves!!!

 

[briggsy]

You are wise to notice this could be a problem. Small tanks fill quickly and some even at the rates you described (200 GPM and 350 psi). Most of the trucks are lower than that but the hydraulic units can achieve these numbers. The fact that the vessel is a 250 psi unit helps. If this were a less than 150 psi unit Air Products would not fill it without a fill line closure device or an engineered orifice. This came from the death of a delivery driver when a vessel exploded from being overfilled, and the relief devices could not handle the volume that the truck was delivering. I have information on the incident and the fill line closure device (FLCD) if you are interested in another level of protection.

Close attention to the pressure should keep you and others safe even with the system you have..