Presentation on theme: "Compressed Gas Safety for Laboratories"— Presentation transcript:
1 Compressed Gas Safety for Laboratories Discussion topics:Potential hazardsSafety considerations regarding:Selecting/ Receiving gasesHandling cylindersUse & StorageResearch Experiments & SystemsEmergency proceduresStanford UniversityEnvironmental Health & SafetyOccupational Health & Safety Program,,Stanford Fire Marshal’s Office,Conmpressedgas.Rev pptIH Report#: / SUFMO #02-00
2 Additional Training Will Be Required This training provides information about safe handling, storage and general hazards of compressed gases. It does not provide specific detailed training necessary to safely install or use compressed gases. Prior to actual use of any compressed gases your supervisor will need to provide operation specific training in this area.If you don’t understand ask questions!If you forget ask questions!If it doesn’t seem right ask questions!We would rather answer questions than deal with a accident……
3 Regulations for Compressed Gas Use & Storage Compressed gas use & storage are regulated by different organizations.California Fire CodeOccupational Safety & Health Administration (CalOSHA)Santa Clara County Environmental Health Department
4 Characteristics of Gases Gases are much lighter than liquids & solids.The molecules of a gas are always in motion.Escaped gases will eventually distribute themselves throughout the air in a room or other confined space.Some gases have odors, some do not.Most gases are invisible, some can be seen.All gases have some property that can be hazardous to you.
6 Potential Hazards High Pressure Asphyxiation Flammability Explosion ToxicityCorrosionOxidationPyrophoricCryogenicPhysical hazards:- PRESSURE: Valve breakoff, regulator failure. BAD!Health hazards:- asphyxiation (by physiological effect or gas can just force out oxygen in the air) Min 19.5% O2 for normal body function- specific toxicityChemical hazards: (reactivity)- flammable gases- explosion w/ reactives:oxygen+ oilother oxidizers (Cl2, F2, nitrous oxide, nitrogen trifluoride), acetylene w/ copper contact- pyrophorics (silane, phosphine, arsine, etc.)- corrosives: special metals for fittingsGas InfoFor research uses, you need to be knowledgeable of the specific gases you are working with. For reference info of hazards & safe use, a good source is the:- Gas Data Book, Matheson
7 Purchasing/ Receiving Gases REDUCE YOUR RISKS!Select the lowest concentration of hazardous gas that will allow you to perform your experiment.Purchase the smallest quantities to satisfy your research needs.Select only gases that are delivered in returnable containersWhen receiving gas cylinders:Check for leaksVisually inspect for damageEnsure valve cover and shipping cap are properly in place.Check that cylinder is properly labeledConsider Gas generators: If extremely hi volumes of a particular gas is used on a semi-permanent basis, this eqpt. can help eliminate risks assoc. with cylinder changeouts.Smaller containers to avoid long storage time of gas cylinders. You should only purchase enough to use in 2 months. Less items stored = less riskUse returnable containers to reduce waste. Minimize purchase of lecture bottles. Very costly to dispose of.Proper labeling: Do not accept cylinders that are not IDed by name. Cannot rely on color coding.
8 Cylinder Story Cylinders come in different sizes, shapes and colors TAKE NOTE:Height & diameter = high center of gravity = not stablePressure = enough to cause deadly damage, unguided missileThus, special precautions for handling, storage, and useRemember the gas supplier must label the cylinder with the contentsCheck the label before you accept, move or use the cylinder.
9 Safe Handling of Gas Cylinders Before handling, make sure that valve cap is securedTransport gas cylinders using only a suitable cartAlways take the safest most direct route whentransporting gas cylindersNever leave un-restrained cylinders un-attended
10 Safe Storage of Compressed Gas Cylinders Only store cylinders in authorized locations.Separation of incompatibles (check SU storage group information)Restricted access to compressed gas cylinder storage.Store away from main building access/ egress pointsSeparation of incompatibles:- 20 feet or proper firewall (non-combustible partition)--contact SU Fire MarshallRestricted access to avoid tampering by unauthorized personnelElectrical circuit-- especially careful during arc welding
11 Safe Storage of Compressed Gases Attach valve cap when a gas cylinder is not in serviceCylinders must be stored uprightMetal restraints at 1/3 AND 2/3 height of cylinderMax of 2 gas cylinders per set of chainsStore upright: - helps prevent damage to valve- for liquid-fuel gases, ensures vapor phase to be incontact w/ pressure relief valve- to allow safe pressurereliefBench clamps: As proven in the Loma Prieta earthquake in ‘89, these bench clamps perform very poorly as a means of securing.EXCEPTION: allowed if bolted to the benchtop w/ cylinder stand.Per SC County, any regulator not connected to a process must be removed from the cylinder, and cylinder capped.Cylinder bench clampsare NOT allowed
12 Safe Use of Compressed Gases DO NOT tamper with the stem and cylinder valvesNEVER use damaged regulators, connectors, piping, etc.For cylinders in use, cylinder valves must have hand wheel attachedClose cylinder valve whenever:work is finishedcylinder is emptyLabel empty cylindersEnsure safe & proper exhaust for purging & pressure relief for toxic, flammable, or corrosive gasesVisual inspection of cylinder/ eqpt: Ensure no substantial corrosion. If suspect, contact supplier or EH&S Fire Safety for evaluation. Replace parts if necessary.Attachment: General Inspection ChecklistWhen calling supplier, provide:- nature of problem- cylinder’s serial #Valve closed when:- work finished to-- lower risk of regulator failure- cylinder empty to-- avoid contamination of cylinder
13 Additional Precautions Some gases require special permits and controls for use. These aretoxic, corrosive, flammable and pyrophoric gases. Checkwith SU EH&S during the design of the experiment in order tounderstand the permitting and engineering control requirements.For these gases, refer to attached information for specific safety precautionsOXIDIZERS: oxygen, nitrous oxide, Cl2, F2,Nitrogen trifluoride, etc.- prevent contact w/ oil, grease, or other combustiblesCORROSIVES: Cl2, F2, HCl, HF, NH3, etc.- proper maintenance of valves, regulators, etc. impt.ACETYLENE:- Incompatibility w/ copper, silver, mercury- regulators specific for acetyleneCRYOGENIC LIQUIDS: N2, He, O2, Ar, Ne, etc.- Extreme cold can freeze human tissue on contact- Piping must integrate pressure relief devicesTOXIC GASES: Ammonia, Arsine, Cl2, F2,CO, Et0, ClO2, etc.- Tightly regulated use. Contact the EH&S Lab Health &Safety Program Mgr.
14 Research Experiments and Systems Label all gas linesRemember to check safety devices (check valves, flow restrictors, pressure gauges, regulators)Select proper construction materialsLeak test system before start-up & at cylinder changesCheck for proper exhaust ventilation for the lab and apparatus prior to opening gas cylinders- Flow restrictors: Restricted Flow Orifices (RFOs)- Check valves: To protect from over-pressure & to prevent backflow- If designing a piping system for flammables, oxidizers, or pyrophorics, avoid using low-melting point metals (copper, brass, etc.) as specified in the fire codes. Stainless is preferred by the Fire Marshall’s Office. Also can refer to the Matheson’s Gas Data Book.
15 Emergency Procedures Standard Operating Procedures (SOP) BE PREPARED! Bottom line….Not only are they a good idea, they are required!BE PREPARED!Know your emergency proceduresKnow your emergency contactsKnow what to do “if” the unexpected happensREFER to attached sheet for general tips on compressed gas emergencies
16 For More Information EH&S Compressed Gas training Guide to Safe Handling of Compressed Gases, MathesonHandbook of Compressed Gases, Compressed Gas AssociationGas Data Book, MathesonOccupational Health & Safety Program- EH&SLing Sue Teng, ,Stanford Fire Marshal’s Office- EH&SJoseph Leung, ,