Nick Barilo
April 24, 2015

Welcome to the General discussion forum!  This forum is meant to provide participants an opportunity to discuss topics on hydrogen and fuel cell technologies.  Our goal is to facilitate collaboration and help participants find and share solutions to enable the timely and safe deployment and use of facilities and equipment.

October 7, 2016

Hi I am a trainer on hydrogen. 

My question is, if a employee open the top fill and the bottom fill valve to do a fast delivery, what is the reel impact of hazard. Or if creat more pressure to puch more fast the product to accelerate the transfer. I know first he does not respect the procedure of delevery. And what I can do to make sure  his security?

Nick Barilo
October 7, 2016

Jonathon, it's not clear from your message, but it looks like you are describing a liquid hydrogen delivery. Liquid hydrogen tanks typically have both "top" and "bottom" fill valves.  The valves are adjusted by the driver to maintain a specific pressure range in the tank so the customer is not impacted by the delivery.  If pressure is rising, the driver will "top" fill more so he can recondense the vapor in the tank and reduce pressure.  If pressure is dropping, the driver will "bottom" fill more to use the incoming liquid as a piston at the bottom of the tank and thereby compressing the vapor in the top.  There is no harm in doing both at the same time by throttling both valves to balance the pressure.  When complete, the driver will tightly shut both valves.  If both the valves are left open, or if both the valves leak, then a pressure build circuit can be formed as liquid from the bottom will flow by gravity into the fill circuit, boil, and then return to the top of the tank.

Originally posted by nick on 7:50 AM Fri Oct 7, 2016

October 8, 2016

Tank you in reply to my question Nick. Because I know we have the employees work dangerously with this product and found a way to work more fast.

I have another question . One of the employe ask me, (this is normal when I open my top fill the liquide does not want enter in the tank. After to knock with my hammer, I heard a sound like a ice pass inside the pipe.)

I know it is really importante to make a good purge before fill the tank. Do you have a documents they talke about that.


P.S.: I am a french men and it is reason why I have the difficulty to ask my questions.  

October 29, 2017

Purging the fill lines is critical to assuring a safe, operational tanks.  This should be standard procedure in all cases.  In most cases helium is used as the purge gas as it is inert and does not solidify  at liquid hydrogen temperatures.  If air is allowed into the liquid hydrogen tank, besides potential for oxygen in the tank, the air will freeze solid and block lines, especially small lines, such as the liqudi level gauge lines (usually 1/4"or ~6 mm).  Since the solid air is denser than liquid hydrogen, the solid air ends up in the bottom of the tank.  Refer to the Compressed Gas Association pamphlet H-5 Installation Standard for Bulk Hydrogen Systems for more information.