- 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).
- 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.
- 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.
- 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.
- 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”.
- 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.
- 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