Procedure to change compressed gas cylinders:

Joe von Fischer Lab: http://rydberg.biology.colostate.edu/~jcvflab/
December 2005, AK

Safety Note: Never allow gas cylinders to fall (aka flying bombs). Keep caps on while moving cylinders and use a gas cylinder cart while transporting long distances. Keep stored gas cylinders secure at all times.
  1. Change compressed gas cylinders when the first stage (gauge closest to the tank valve) reads 100 psi. Note: The carrier gases (5.0 UHP N2 for the Shimadzu and 5.0 UHP He for the Fisions) need to be changed overnight and allowed to equilibrate for at least 12 hours. Never allow a carrier gas cylinder to go completely empty (the company will charge extra if that happens). If the first stage on the carrier gas is reading 200psi, you may want to change it before the weekend. The H2 and breathing air can be changed ½ hour before a run, with no problem. Note: The breathing air on the Shimadzu needs to be changed about every 9 days, the carrier every month, and the H2 every two months, approx. Also note: if the first stage gauge reads zero, you won’t have enough gas to last a full run (then second stage goes down fast). 

  2. Move new cylinder by old gas cylinder and remove cap. Clean the inside fitting with a Kimwipe to insure a good seal between the tank and regulator. Remove the small yellow cap in the new carrier gas and set aside to replace in the old tank. 

  3. Close the second stage valve (small black, clockwise to the right) and the tank valve (clockwise also to the right) on the tank to replace. This will minimize air getting into the GC copper lines. Remove the regulator with a large crescent wrench. Note: on normal threaded fittings left or up =off, and right or down=on. On reverse threaded fittings (for H2 tank, with mark) right or down=off and left or up=on. Use the crescent wrench to remove the regulator part way, then use your fingers to remove the regulator off the old tank. Note: You may hear some air releasing from the tank when you first use the wrench to pull off the regulator, if you keep hearing it, the tank valve isn’t shut off completely. 

  4. While holding the regulator in one hand, carefully move the old tank away and put the new one into the cylinder wall strap. I usually grasp the tanks by the top valves when moving them. Finger-tighten the regulator fitting onto the tank, then use the crescent wrench to snug the fitting down. Note: do not over-tighten the fittings, doing so will cause the cylinders to leak and the CGA fittings will need to be replaced. Note: please double check the gas pressure on the second stage gauge (adjusted by moving the large black knob on the front of the regulator)-see GC specs for details. In general, the large black knob should never be moved to keep the gas pressure consistent. 

  5. Open the second stage and gas cylinder valve. Snoop between all the connections between the tank and the regulator, the second stage valve and the regulator to the line. A leak will show up as lots of bubbles. Replace the cap (and small yellow insert for carrier gases) on the old cylinder and mark the tank as ‘EMPTY”. 

  6. Light the FID if you’ve replaced the hydrogen or the air. This is done by pressing the "Inj." button down by the valve port on the Shimadzu, while simultaneously using the lighter near the (caution-hot!) silver flame port (see me for more details). The Fisions has a small green button to internally light the FID. Sometimes it helps to unscrew the top silver flame cap on the Fisions (caution: very hot-use a Kimwipe or heat glove), then light the flame. Check to see if there’s any condensation coming from the lit flame using a shiny object or mirror at the flame port. Note: If there are no peaks coming off the FID, there’s a good chance the flame is not lit. 

  7. Be sure to store all new and used cylinders securely to the wall, or cylinder strap and that the used cylinders are marked "EMPTY" and the date and type of gas changed is recorded in the red Shimadzu book/Maintenance.