Safe Handling of Compressed Gases Reasons for

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. 173. 300(a)].

The Gas: Rule #1! Know the properties of the materials involved Gases may be: • Under high pressure • Toxic • Corrosive • Flammable • Pyrophoric • Oxidizers

High Pressure Gas • 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.

Toxic Gases • Have the ability to cause injury or death when ingested or absorbed by the skin • Examples include Ammonia, Vinyl Chloride and Phosgene

Corrosive 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

Flammable & Pyrophoric 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

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 (105 -115 F; 41 -46 C).

Threshold Limit Values (TLV’s) • 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 1 A 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 1 Specification number consists of three sections. • DOT- signifies that the cylinder conforms to Department of Transportation (DOT) specification. • 3 AA - specifies type and material of cylinder construction. • 2265 - indicates service pressure for which the cylinder is designed at 70 F.

Cylinder Identification And Markings 2 Cylinder serial number (Matheson Tri-Gas number)

Cylinder Identification And Markings 3 Date of initial hydrostatic testing

Cylinder Identification And Markings 4 Original inspector's insignia

Cylinder Retest Schedule Specification under which cylinder was made Minimum retest pressure (psi) Retest period (years DOT-3 3000 psi 5 3 D 5/3 times service pressure 5 4 700 psi 10 DOT-9 400 psi (maximum 600 psi) 5 26 for filling at over 450 psi 5/3 times service pressure 5 33 800 psi 5

CGA Connections • Compressed Gas Assoc. • Reasons for CGA standards • CGA gaskets/washers • Restricted flow orifices

CGA Connections

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 shouldn’t 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. • Don’t use the protective valve caps for moving or lifting the cylinders.

Cylinder Handling and Transportation • Don’t 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

Cylinder Storage • • 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

Pressure Regulators and How They Work

Single Stage Regulator Outlet gauge Inlet gauge Temporary shut-off valve CGA inlet connection P/A knob

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 in “two 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 Applications: • Recommended for continuous use applications, such as carrier gas supply to GC’s or other analytical instruments, where it is critical that a constant delivery set pressure be maintained

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

Regulator Operation • 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 Failures • 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)

Safety Devices: • 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

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. ”

Consider Reduction/elimination of gas cyl’s in the lab • Through a centralized gas distribution system • Gas generators for H 2, N 2 or Zero Air

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

Additional Safety Information

Safety is our First Priority

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