Documentation:Gas Tank Handling and Regulator Use

General Handling, Use, and Transport

Obtain training using gas cylinders from qualified personnel before using or transporting tanks (including: transportation, how to use a cylinder, and removing/installing a regulator).
Always use a gas cylinder cart for transport (MCML 136, 112, 230).
Always roll the cart in front of you, don’t pull it towards you.
Chain or strap tanks in upright position.
Keep the protective cap in place while moving the cylinder.
Never ride in the elevator with the gas tank.
Keep cylinder valves closed when not in use.
Do not place cylinders near exit route and doors.
Store away from heat, sun and sources of moisture.
In the lab keep only those cylinders that are actually in use.
Store the smallest size that is available & practical.
Protect cylinders from any objects that might cut or scrape them.
Do not drop cylinders or otherwise permit them to strike each other.
Store according to compatibility groups.
Review MSDS for gas specific information.
Examine and make note pressure levels after every use, and change tanks before they are empty (approximately 150 psi) to reduce the risk of running out of a gas during important analysis and to reduce risk of contaminating your instrument from materials adsorbed or condensed on cylinder walls.

Swapping a Gas Tank

Gas tank regulator with notches, notched regulator

Coordinate with your supervisor to get a new gas tank delivered to MacMillan.
The tank will be delivered to the cage behind MacMillan, near the loading bay. Coordinate with Lewis Fausak (APBI Technician), Zoran Nesic (LFS Engineer), or Andy Jeffries (LFS Operations) to obtain access and a cart.
Tighten the valve on the old tank.
Unscrew the regulator from the old cylinder using a wrench (can borrow from Lewis or Zoran). Be careful of the direction to avoid overtightening the regulator, which can damage the threads. Fittings with a notch close by rotating counterclockwise. One of the regulators has a notch on it for which direction is open, all regulators of this type with a vertical line will open clockwise, ones without a line will open counter clockwise.
You can now carefully move the old cylinder away and replace it with a new one. Make sure the new cylinder is secured with the belt, rip off the tag to indicate that it is in use. Rip off the tag from the old cylinder to indicate that it is empty.
Use the proper regulator for a particular gas. A CGA number should be stamped somewhere on the regulator. You can search this online for the intended gas service.
Check that the regulator is not obviously damaged:
- Make sure it has the necessary gauges and that they are all reading zero.
- Make sure the threads of the regulator fitting are clean and not damaged.
- Carefully inspect wetted parts for grease or oil. Oxidizing gases (e.g. oxygen) can react explosively with traces of combustible material. If you suspect any contamination clean it off with Simple Green or another suitable degreaser.
- Make sure that the threads of the gas cylinder do not appear damaged and also are clean. Use your finder to clean the conical (sealing) part of the tank fitting and check for damage or scratches, which could lead to leaks. NOTE: connecting piping and fittings are all wetted parts.
- Hold the regulator with one hand and carefully thread the fitting onto the tank. Oxidizing gases and inert gases have normal “right hand” threads (tighten by turning clockwise); reducing gases (fuels) have “left hand” threads (tighten by turning counterclockwise). Hand tighten. It may be helpful to gently wriggle the regulator as you tighten the fitting.
- Use a 1 ¹/₈ inch wrench to tighten the regulator onto the tank with one ½ turn. It is better to undertighten and leak test, than to overtighten and damage the regulator.
- Do not overtighten. If you do the threads can be damaged. Severe overtightening can strip the threads and cause the regulator to fly off the tank when the valve is opened. This could cause severe injury.
Never use Teflon tape (or any other lubricant or sealant) on the tank threads. These are parallel threads and Teflon tape will not help prevent leaks; it might make them worse.
Teflon tape should only be used to assist sealing of pipe threads. These are tapered threads that tighten as they enter the outer threaded housing.
Once the regulator is tight, ensure that the outlet valve is closed and the pressure adjusting valve is fully threaded out (no pressure delivered to the outlet).
Stand so that you are not facing the tank outlet. If the regulator were to come off upon opening the tank valve you need to be off the line of travel.
Close the regulator. Turn the adjusting knob to the fullest counter clockwise position. The regulator must be closed before opening the cylinder to avoid the chance of damaging the diaphragm and allowing high cylinder pressure downstream of the regulator. Always open the gas cylinder slowly to avoid pressure shocks to the regulator.
Carefully open the tank valve. Listen for hissing that might indicate a major leak. If you hear hissing close the tank valve. You can try tightening the regulator more, but, as indicated above, do NOT overtighten it. Use “Snoop” (soap and water) solution applied to the connections can be used to check for small leaks. After applying snoop, bubbles would indicate a leak. Call in the lab manager or other qualified personnel to assist with regulator issues.
When there are no bubbles, it’s time to adjust the output pressure.
Set the delivery pressure on the regulator (should already be marked by a sharpie). Do not overshoot.
After installing the regulator on a new cylinder, it is best to let the instrument run for a few minutes to purge before running the samples.
After you replace the cylinder, return the empty cylinder to the “Empty Cylinders” area of the gas tank room cages and call Praxair to let them know it is ready for pickup.
If not using the regulators for extended time, store them in a sealed plastic bag. Make sure it has a tag that describes its intended gas service. Report any defective regulators so they can be sent out for repair.