Presentation on theme: "Compressed Gas Safety for Laboratories"— Presentation transcript:
1 Compressed Gas Safety for Laboratories Discussion topics:Potential hazardsSafety considerations regarding:- Selecting/ Receiving gases- Handling cylinders- Storage- UseResearch apparatus/ systemsProper emergency proceduresStanford UniversityEnvironmental Health & SafetyOccupational Health & Safety Program,x5-3209,Stanford Fire Marshal’s OfficeX3-0609,Conmpressedgas.Rev pptIH Report#: / SUFMO #02-00
2 Health & Safety Regulations- Compressed Gas Cylinders (CGCs) Safety regulations (Cal/OSHA 8 CCR , California Fire Code Article 74 & 80) cover:Labeling & Construction of CGCsSafe handling of CGCsSafe use of CGCsSafe storage of CGSsCal/OSHA regulations online:
3 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.
4 Types of GasesNon-liquefied Compressed Gases – Nitrogen, Argon, Helium, Oxygen, HydrogenLiquefied Compressed Gases-Chlorine, Hydrogen chloride, Carbon Dioxide, Nitrous OxideCompressed Gases in a Solution-AcetyleneCryogenic Liquefied Gases-Nitrogen, Argon, Helium, Oxygen, Hydrogen
5 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
6 Purchasing/ Receiving Gases REDUCE YOUR RISKS!Select least hazardous gases that will workPurchase only necessary quantitiesSelect gases w/ returnable containersWhen receiving gas cylinders:Check for leaksVisually inspect for damageEnsure valve cover and shipping cap is onCheck for proper labelingConsider 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.
7 Cylinder Story Cylinders come in different sizes, shapes and colors NameDOT Hazard ClassTAKE 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.
8 Safe Handling of CGCs Before handling, ensure valve cap is secured Transport CGCs using a suitable cartNever rely on valve cap as a handholdAlways take the safest route fortransportDo not leave un-restrained cylinders un-attended
9 Safe Storage of Compressed Gas Cylinders CGC storage area requirements:Protected from:external heat sourcespassing/ falling objectsWell-ventilatedIsolation from highly flammable materials (>20 ft)Separation of incompatibles (check SU storage group information)Restricted access to CGCsAway from main access/ egress pointsAvoid forming part of an electrical circuit with the CGC(Safe storage- cont’d.)Separation 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
10 Safe Storage of Compressed Gases Attach valve cap when CGC is not in serviceCGCs shall be held in a suitable rack or secured to other rigid structuresCylinders must be stored uprightMetal restraints at 1/3 AND 2/3 height of cylinderMax of 2 CGCs per set of chainsCylinder bench clamps are NOT allowedStore 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.
11 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 gasesNever use cylinders as rollers or supportsVisual 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
12 Safe Use CGCs-- Special Precautions Some gases require special permits and controls for operation. Toxic,corrosive, flammable and pyrophoric gases are examples. Checkwith your P.I., safety representative or SU EH&S before orderingany of these materials.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.
13 Research Apparatus/ Systems CGCs shall be equipped with connections complying with ANSI B / CGA (Cylinder Valve Outlet & Inlet Connections)Label all gas linesRemember safety devices (check valves, flow restrictors)Pressure gaugesSelect proper construction materialsLeak test system before start-upEnsure exhaust ventilation for the lab and apparatus is on and working normally prior to opening CGC’s- 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.
14 Emergency Procedures BE PREPARED! Know your emergency shutdown proceduresKnow your emergency contactsKnow what to do “if” the unexpected happensGuidance on standard and emergency procedures:SOP’s are not only good ideas they are requiredLaboratory supervisor or local safety coordinatorSU Health & Safety ManualREFER to attached sheet for general tips on compressed gas emergencies
15 For More InformationGuide 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, ,