Presentation on theme: "Safe Handling of Compressed Gases. Reasons for a Safety Seminar To heighten the awareness of the dangers associated with compressed gases To encourage."— Presentation transcript:
Safe Handling of Compressed Gases
Reasons for a Safety Seminar To heighten the awareness of the dangers associated with compressed gases To encourage safe operating practices in their everyday use To help ensure the right equipment is used for your application
Definition Compressed Gas Any material or mixture with an in-container pressure exceeding 40 psia at 70 F, or a pressure exceeding 104 psia at 130 F, or any liquid flammable material having a vapor pressure exceeding 40 psia at 100 F [sec (a)].
The Gas: Rule #1! Know the properties of the materials involved Gases may be: Under high pressure Toxic Corrosive Flammable Pyrophoric Oxidizers
Can cause equip. to fail with explosive force When released can diffuse into the atmosphere very rapidly, and an entire room may be thoroughly contaminated within seconds! A common 9 dia X 52 high cylinder pressurized to 2000 psi has the stored energy equivalent to one pound of dynamite! Cylinders are commonly filled to standard pressures of 2000 psi, 2490 psi, 3500 psi and 6000 psi. High Pressure Gas
Have the ability to cause injury or death when ingested or absorbed by the skin Examples include Ammonia, Vinyl Chloride and Phosgene Toxic Gases
Will attack and damage human tissue Will have an adverse effect on improper materials of construction Examples of corrosive materials are Hydrogen Chloride, Hydrogen Fluoride Corrosive Gases
Flammable gases easily catch fire and burn rapidly in air Examples of flammable gases are Acetylene, Hydrogen, Propane, and Propylene Pyrophoric gases spontaneously ignite and burn when exposed to the atmosphere Silane is a pyrophoric gas which is commonly used in the electronics industry Flammable & Pyrophoric Gases
Liquefied Compressed Gases Contents of a liquefied compressed gas cannot be determined by the pressure in the cylinder, and a cylinder scale must be used
Shipping Regulations Dept. of Transport (D.O.T.) regulations specify the familiar diamond shaped tag that must be affixed to each cylinder being shipped
Material Safety Data Sheets Required in workplace Substance fact sheet listing characteristics, hazards and as much detail as possible concerning the particular gas SECTION 4 FIRST AID MEASURES INHALATION: If adverse effects occur, remove to uncontaminated area. Give artificial respiration if not breathing. If breathing is difficult, oxygen should be administered by qualified personnel. Get immediate medical attention. SKIN CONTACT: If frostbite or freezing occur, immediately flush with plenty of lukewarm water ( F; C).
Threshold Limit Values (TLVs) Time Weighted Average (TWA) - Average 8 hour exposure, 5 days a week Short Term Exposure Limit (STEL) - 15 minutes, 4 times a day Immediately Dangerous to Life and Health (IDLH)
Personal & Fixed Gas Monitors
Compressed Gas Cylinders Come in many shapes and sizes Commonly constructed of Carbon Steel or Aluminum Standard size 1A cylinder pressurized to 2200 psig holds approx. 225 ft 3 of gas in an internal volume of 1 ½ ft 3 !
Cylinder Identification And Markings DOT- signifies that the cylinder conforms to Department of Transportation (DOT) specification. 3AA - specifies type and material of cylinder construction indicates service pressure for which the cylinder is designed at 70 F. Specification number - consists of three sections. 1
Cylinder Identification And Markings Cylinder serial number (Matheson Tri-Gas number) 2
Cylinder Identification And Markings Date of initial hydrostatic testing 3
Cylinder Identification And Markings Original inspector's insignia 4
Cylinder Retest Schedule Specification under which Minimum Retest cylinder was maderetest pressure (psi) period (years DOT psi5 3D5/3 times service pressure psi10 DOT-9400 psi (maximum 600 psi)5 26 for filling at over 450 psi5/3 times service pressure psi5
CGA Connections Compressed Gas Assoc. Reasons for CGA standards CGA gaskets/washers Restricted flow orifices
Matheson Tri-Gas Product Safety & Code Compliance Primary Governing Bodies / Safety Codes Compressed Gas Association (CGA) Semiconductor Equipment & Materials International (SEMI) US Environmental Protection Agency (EPA) Uniform Fire Code / Local City Regulatory Committee (UFC) Uniform Building Code (UBC) / BOCA National Fire Prevention Code (NFPC) International Conference of Building Officials (IBOC) Toxic Gas Ordinance (TGO)
Cylinder Handling and Transportation Upon receipt, visually inspect the cylinders for obvious defects such as dents, large amounts of rust and missing or loose safety caps. Cylinders shouldnt be accepted unless identified with the appropriate labeling, and all them agree with one another! Use a cylinder cart and secure the cylinders with a chain when moving. Dont use the protective valve caps for moving or lifting the cylinders.
Cylinder Handling and Transportation Dont drop a cylinder, permit them to strike each other violently or be handled roughly. Unless cylinders are secured, regulators should be removed, valves closed and protective caps in place before cylinders are moved. Rolling cylinders in a vertical position on the bottom edge is to be avoided as much as possible. Gas cylinders must never be dragged or rolled in the horizontal position.
Cylinder Storage Double restrain cylinders with non-combustible material (i.e., chain) Label Full versus Empty Signs for hazardous gases Keep away from traffic areas Store in fire resistant, well ventilated, dry areas
Keep away from flames or sparks Keep caps on when not in use Store in areas <125°F Keep oxidizers 20 ft. from flammables Corrosives should be stored less than 6 months Cylinder Storage
Single Stage Regulator Reduces the inlet supply pressure in one step, from the inlet supply pressure to the final outlet pressure
Single Stage Regulator Applications: Intermittent use - where a sample of gas is required from a cylinder Where pressure rise in a set delivery pressure is not critical As a line regulator where there is a second pressure regulator at the gas supply source
Single Stage Regulator Characteristics: Rule of thumb: for every 100 psig drop on the inlet pressure, there will be 1 psig rise on the outlet working pressure
Two-Stage Regulator Reduces the pressure intwo steps from a high pressure inlet source, to the final outlet working pressure
Two-Stage Regulator Characteristics: Delivery set pressure remains constant as the inlet supply pressure decays Becomes a single stage regulator when the source supply pressure becomes less than the set pressure of the first stage (~300 psig) Can be supplied with an inter-stage relief valve as insurance in the event of first stage seat failure
Two-Stage Regulator Recommended for continuous use applications, such as carrier gas supply to GCs or other analytical instruments, where it is critical that a constant delivery set pressure be maintained Applications:
Regulator Installation Do not use CGA adaptors or change CGA connections on regulators for a different gas service – unless work is done by qualified personnel! Always ensure there are no nicks and scratches on regulator CGA connections Never use Teflon tape to achieve a proper seal Always leak check connections using a soap bubble solution or electronic leak detector
Always ensure the P/A knob is backed off counterclockwise to ensure there is no load on the regulator load spring – prior to opening the cyl valve! Never open a cylinder valve all the way. 1 ½ to 2 turns is usually sufficient Always stand with the cylinder valve between you and the regulator when opening the cylinder valve and/or adjusting pressure on the regulator Do not use the temporary shut-off valve to turn off gas flow if the shut-off duration will be longer than 20 min. Use cross or T-purge assemblies if regulators are to be used for toxic or corrosive gases! Regulator Operation
95% of regulator failures are due to seat failures, caused by: –Corrosion buildup on the seat –Contamination (dirt, metal filings, Teflon tape) that scores the seat at a high velocity Set pressure creep on the delivery pressure gauge indicates a seat failure! Regulator Failures
A Pressure gauge that will not read zero indicates the bourdon tube has been damaged and the gauge must be replaced! Gas leaking through the bonnet assembly of the regulator indicates a diaphragm failure (Typically caused by failure to ensure the regulator is shut off prior to installing it on a new cylinder) Regulator Failures
Check valve: prevents reverse gas flow Flash Arrestor: prevents ignition source from reaching regulator and cylinder for flammables Excess Flow Valve: restricts flow in the event of a gas line break Safety Devices:
Things Not To Do! Never roll a cylinder to move it. Never carry a cylinder by the valve. Never leave a cylinder unsecured. Never force improper attachments on to the wrong cylinder. Never grease or oil the regulator, valve or fittings of an oxygen cylinder. Never refill a cylinder. Never attempt to mix gases in a cylinder.
Safe Gas Usage Compressed gases serve laboratories and industrial plants in many ways, but the cylinders and gases present a number of hazards. Treat all gas cylinders, full or empty, as objects that have a very real potential to injure you severely.
Reduction/elimination of gas cyls in the lab Through a centralized gas distribution system Gas generators for H2, N2 or Zero Air Consider
Emergency Plan Every location where compressed gases are handled should have a written emergency plan covering steps to be taken in the event of an accidental release of gas This plan should consider the nature of the gases being handled, that is their chemical and physical properties
Plan Elements At a minimum, the plan should specify the following : Alarm System & Evacuation Procedure Response Personnel Emergency Equipment Containment or disposal methods
Additional Safety Information
Safety is our First Priority
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