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Safe Handling of Compressed Gases

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Presentation on theme: "Safe Handling of Compressed Gases"— Presentation transcript:

1 Safe Handling of Compressed Gases

2 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

3 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)].

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

5 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.

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

7 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

8 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

9 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

10 Shipping Regulations Dept. of Transport (D.O.T.) regulations specify the familiar diamond shaped tag that must be affixed to each cylinder being shipped

11 Material Safety Data Sheets
Required in workplace Substance fact sheet listing characteristics, hazards and as much detail as possible concerning the particular gas SECTION 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).

12 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)

13 Personal & Fixed Gas Monitors

14 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 ft3 of gas in an internal volume of 1 ½ ft3!

15 Cylinder Identification And Markings
1 Specification number - consists of three sections. 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.

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

17 Cylinder Identification And Markings
3 Date of initial hydrostatic testing

18 Cylinder Identification And Markings
4 Original inspector's insignia

19 Cylinder Retest Schedule
Specification under which Minimum Retest cylinder was made retest pressure (psi) period (years DOT psi 5 3D 5/3 times service pressure 5 psi 10 DOT psi (maximum 600 psi) 5 26 for filling at over 450 psi 5/3 times service pressure 5 psi 5

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

21 CGA Connections

22 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)

23 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.

24 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.

25 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

26 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

27 Pressure Regulators and How They Work

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

29 Single Stage Regulator
Reduces the inlet supply pressure in “one step”, from the inlet supply pressure to the final outlet pressure

30 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

31 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

32 Two-Stage Regulator Reduces the pressure in “two steps” from a high pressure inlet source, to the final outlet working pressure

33 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

34 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

35 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

36 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!

37 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!

38 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)

39 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

40 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.

41 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.”

42 Consider Reduction/elimination of gas cyl’s in the lab
Through a centralized gas distribution system Gas generators for H2, N2 or Zero Air

43 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

44 At a minimum, the plan should specify the following :
Plan Elements At a minimum, the plan should specify the following : Alarm System & Evacuation Procedure Response Personnel Emergency Equipment Containment or disposal methods

45 Additional Safety Information

46 Additional Safety Information

47 Safety is our First Priority

48 All rights reserved. No part of this presentation may be reproduced or used in any form whatsoever without the express written permission of Matheson Tri-Gas, Inc.; except in the case of brief quotations embodied in critical articles and reviews. The information contained here is for the personal use of the reader and may not be incorporated in publications, databases, or software programs without the written consent of Matheson Tri-Gas, Inc. This publication is intended to provide accurate information in regard to the subject matter covered and has been obtained from sources believed to be reliable. Of necessity the information is abbreviated and other information, training and/or education is required of the user of this information. Accordingly, Matheson Tri-Gas, Inc. makes no warrantees, guarantees, or representations of any kind or nature with respect to the information published herein, either express or implied, and whether arising by law or otherwise, including but not limited to any implied warranty of merchantability or fitness for any particular purpose, and shall not be responsible for any errors, omissions, or damages arising out of use of this information. Matheson shall in no event be liable for any personal injuries, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication of, or reliance upon the information.


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