1. Properties of gases2. Cylinders3. Storage of Gases4. Regulators5. Cryogenic Liquids

IntroductionIntroduction

All compressed gases by definition can be hazardousKnow the properties of the gases you are working with, meaning you should read your MSDS sheets before using the gasesIt is important to be aware of not only the chemical hazards associated with the gas, but the hazards associated with the physical properties as well

Compressed Gas PropertiesCompressed Gas Properties

High Pressure: high inherent potential energy that can be released during a ruptureAsphyxiant: gases can displace oxygen and make it difficult to breathPyrophoric: gases which under normal conditions ignite upon contact with airCryogenic: gases at very low temperatures that can cause burns or frostbite when in contact with skinInert Gases: gases that do not react with anything, but they areasphyxiantsFlammable : gases that when mixed with an oxidizer in a given range of concentrations can burn

Oxidizing: gases which do not burn, but support and aid combustionCorrosive gases: cause destruction of material or tissue when contact is made, or do so in the presence of moisturePoisonous: produce chemically injurious or lethal effects in humans

Compressed Gas PropertiesCompressed Gas Properties Definition of a Compressed GasDefinition of a Compressed Gas

Any substance contained under pressureIncludes dissolved gas or a gas liquified by compression or refrigerationWith a critical temperature of less than 50° CAbsolute vapour pressure of greater than 275.8kPa @ 21 °C or 717 kPa @ 54 °C or both or any liquid having an absolute vapour pressure exceeding 275.8 KPa@37.8 °C

Example: How dangerours is Example: How dangerours is Nitrogen?Nitrogen?

Nitrogen comprises 78% of our atmosphere, yet it was responsible for 80 deaths between 1992 and 2002Occurred in laboratories, medical facilities, industrial plantsNitrogen and Helium are such hazards that NMR facilities use Oxygen sensors to ensure that the air is breathable at all times

Properties of CylindersProperties of Cylinders

Heavy, smooth, hard to gripUp to 57 inches (~140 cm) tallCan weight up to 150 lbsHave been know to cause injury and even death in some circumstancesPhysical hazards include tipping, rolling, uncontrolled projectile, bounce, pinning

1. Cylinder Cap2. Valve Handwheel3. Valve Outlet Connection4. Valve Pack Nut5. Pressure relief valve6. Valve Outlet Cap7. Cylinder Collar8. DOT/Cylinder type & PSI rating9. Cylinder serial number10. Initial hydrostatic test date11. First 5 year hydrostatic retest12. “ ” qualifies for 10 year retest13. Original inspectors insignia

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11.11. 12.12.13.13.

Standard cylinder outlets have been devised by the Compressed Gas Association (CGA) to prevent mixing of incompatible gasesAs a result, some fittings have either left or right handed threads, some internal, some externalOne should never change the adaptor on a regulator to prevent mixing of incompatible gases

LeftLeft--handed (notched fitting)handed (notched fitting)

RightRight--handedhanded

Cylinder SpecificsCylinder Specifics

Always read the labels, never use cylinders that have no identificationAlways read MSDS sheets prior to useRead your SOP prior to use for specific instructions prior to handlingCylinder colours in no way, shape or form identify their contents, only labels indentify what is contained inside the cylinders

LabelsLabels

Moving of CylindersMoving of Cylinders

You are required to use a cylinder trolley to move a cylinder over even short distancesThe trolley must be either a three or four wheeled cart, two wheels are not sufficientSecure the chain around the cylinder before attempting to move and push the cart, not pull it

Avoid knocking and rolling the cylinders around and be aware that during transport the cylinders can be unstableDo not transport a cylinder without its cap in place, never move it with a regulator installed

Why Do We Secure Cylinders?Why Do We Secure Cylinders?

Cylinders, if they fall over, can become projectiles with such a force that they can smash through brick walls

Storage Location of GasesStorage Location of Gases

Non flammables may be inside or outside of buildingFlammables must be outside of building

Store in approved cages secured with capStore away from heat, sunlight, weatherCorrosive gases should not be kept for a long period of timeCheck recommendation of manufacturerPurchase least amount possible, but use common senseDo not order more than you can use, track what you use and adjust your order

Securing of Gas CylindersSecuring of Gas Cylinders

Gas cylinders must be secured at all times, whether in use or not, empty or fullThey must be attached to the wall, individually to the wall, or placed in a holding cageChains or sturdy straps must be used to secure cylinder ¾ of the way up the cylinder

Types of RegulatorsTypes of Regulators

Two-Stage Low Pressure

Single-StageHigh Pressure

RegulatorsRegulators

Delivery Pressure GaugeDelivery Pressure Gauge

Cylinder Pressure GaugeCylinder Pressure Gauge

Cylinder ConnectionCylinder Connection

Delivery Pressure Adjustment KnobDelivery Pressure Adjustment KnobFlow Control ValveFlow Control Valve

Be certain that the tubing used to carry the gas from the regulator to its end use is compatible with the gas. Example: Copper tubing + acetylene =copper acetylene (explosive)

Fittings for flammable, toxic and air reactive gases need to be checked at each installation on a new cylinderNever use excessive force always use the proper toolsWhen attaching regulator, ensure that it is in the closed positionAfter installation, open valve on cylinder slowly and look to see how much pressure is in the cylinder

Check the regulator connections for leaks with appropriate leak detections equipment approved for the gas (it is up to the PI to ensure that the cylinder is in good condition and leak tested on a regular basis)Never use teflon tape, solvent or grease on the regulator fittingsFor corrosive gases, must use teflon o-ringsIf you feel a cylinder is not in good condition, return it to the supplier

Notes on RegulatorsNotes on RegulatorsInstallation of RegulatorInstallation of Regulator-- Step by Step by

StepStep

Setup your cylinder in its location, ensuring that it is secured to the wall or to the bench top with either a chain or a strapIf it is a toxic, corrosive or air reactive, be sure to set up in a gas cabinet or fumehood

Remove the cap from the cylinderSelect the appropriate regulator for your gas, make sure it has the correct CGA fitting for the cylinderClean the threads of the cylinder with a brass brush or dry kimwipe, ensure that they are in good shapeInspect the regulator CGA fitting threads to make sure they are also in good shapeMake sure that all threads are grease, solvent and teflon tape free

Hand tighten the regulator, be certain to not cross thread it or strip itUse a proper wrench to tighten down, do not over tighten (use a proper box wrench as crescent wrenches tend to strip the regulator fitting)Ensure that all valves on the regulator are closed, then stand so that you are not in the path of any objects should they fly off of the regulator and open the cylinderClose the cylinder and wait ten minutes to see if the pressure decreases to test for leaks Check the other seals immediately with an appropriate method to ensure that there are no leaks

Turn the delivery pressure adjustment pressure knob clockwise until the desired pressure is reached on the delivery pressure guageTurn counter-clockwise to get lower pressure

Closing the CylinderClosing the Cylinder

Close the main valve and bleed the lines if possibleTurn the delivery pressure knob counter clockwiseRemove the regulator from the cylinder and replace the safety capIf the cylinder is empty, remove to empty cylinder storageNever drain a cylinder completely empty

Regulator MaintenanceRegulator Maintenance

Standard visual checks of the regulators before each use to ensure that there is no visible damagePressure check and functional test every 6 monthsSupplier servicing every 2 years

Gas which when compressed in a container becomes liquidAt ordinary temperature and pressure 25 –2500 psigBoiling point range from ¯130 ° to ¯ 30° F (¯90° to ¯ 1°C)@ 70° F (21.1°C) the cylinder contains both liquid and gas

Properties of Liquid NitrogenProperties of Liquid Nitrogen

78% of AtmosphereColorless, Odorless, Tasteless and NontoxicBoils at -320 degrees Fahrenheit (-196 C)Non-FlammableWILL NOT SUPPORT LIFEGas is slightly lighter than air

Characteristics of Cryogenic Liquid Characteristics of Cryogenic Liquid NitrogenNitrogen

Primary Hazards• Asphyxiation• Potential for rupture of containers, pipelines, or systems. When

liquid or even cold vapor is trapped between valves there is thepotential to cause a pressure buildup to a point of violent rupture to a container or piping. (Reliable pressure relief devices are used to prevent this)

• Example:1 cubic foot of liquid nitrogen will expand to 696 cubic feet of100% gaseous nitrogen at 70° FThe nitrogen gas can displace the oxygen in the area, leading toasphyxiationThis is why cryogenic liquids should always be stored in well-ventilated spaces

Oxygen Deficiency: A Big RiskOxygen Deficiency: A Big Risk

Liquid nitrogen, when returned to the gaseous state, can displace oxygen from the air and can create an oxygen-deficient atmosphere under the right conditions.It may be prudent to install oxygen monitors in areas where liquid nitrogen is stored and ventilation is minimal.

Oxygen Deficiency PrecautionsOxygen Deficiency Precautions

• All cryogenic liquids should be used and stored in well-ventilated areas.

• High concentrations of nitrogen reduce the breathable oxygen in the air.

• Filling between containers, leaking valves, and liquid tank venting are some examples that could lead to an oxygen deficient atmosphere.

Handling Liquid NitrogenHandling Liquid Nitrogen

Precautions:• Always wear safety equipment, including heavy loose

fitting leather or cryogenic gloves, and eye and face protection.

• High concentrations of escaping gas should not be allowed to collect in an enclosed area.

• Avoid prolonged breathing of cryogenic liquid vapors .Avoid rough handling of liquid containersA cold outside jacket indicates a loss of vacuum-Contact supervisor or vendorLiquid cylinders should only be moved with proper handling equipment.

Handling Liquid NitrogenHandling Liquid Nitrogen

Prior to use, ensure the fittings on the regulator match the fittings on the liquid containerNever use adaptorsNever attempt to change or remove any fittings

Different Types of DewarsDifferent Types of Dewars Liquid to Gas Conversion in DewarsLiquid to Gas Conversion in Dewars

The liquid-to-gas conversion rate is about 2.3% per day under perfect conditions, so the actual vaporization rate experienced can vary.If gas product is not used, pressure will build until it is released by a control valve.Note that this is a high pressure container, with the gauge marked for 350 psig.

Liquid to Gas ConversionLiquid to Gas Conversion

Since liquid is converted to gas at about 2.3% per day even under ideal container conditions, if the liquid is not used regularly, the vessel will be empty in a certain amount of time.It is important to estimate your use so the liquid will not be wasted.

Storage in Cold RoomsStorage in Cold Rooms

Contrary to popular belief, storage of liquid containers in cold rooms will not slow down the liquid to gas conversion.Storage in cold rooms can actually create an oxygen deficient atmosphere if the room does not have adequate ventilation to remove the nitrogen gas generated.If there is a concern regarding oxygen deficiency in these areas, oxygen deficiency alarms should be installed in these areas.

WarningWarning

Never plug, restrict, or remove any relief device.Never attempt to cap or seal a venting relief device in any way.Ice or frost buildup on a pressure relief valve can be removed with a damp cloth. (Wear proper Personal Protective Equipment (PPE) when removing the frost.)Be aware that frost buildup can freeze open a pressure relief valve, which can then lead to the complete venting of the entire contents of the dewar

Elevator TransportElevator Transport

Use freight elevator if possibleIf a passenger elevator is used, it should be locked out to all other usersDo not transport a liquid container at any time in an elevator with any other personnel in the car unless they have a supplied air respirator

Liquid WithdrawlLiquid Withdrawl

Caution!!Always wear a full face shield, goggles, leather or cryogenic gloves, safety shoes, and aprons when transferring liquid. Ensure that the liquid cannot collect in pants cuffs or travel down into shoes. Do not tuck cuffs into pants! Cuff gloves over sleeves.Transfer of liquids at pressures higher than 22 psig into open vessels such as small dewars can lead to excessive splashing. This could result in injury from freezing of the body part

Liquid WithdrawlLiquid Withdrawl

Ensure that withdrawal hose is equipped with a phase separator to prevent splashing. Check with supervisor or supplier.Never dispense liquid into an unapproved container, such as a Thermos® bottle. It will shatter!