Work with gas

From Biomedhms
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All transportation of gas cylinders and movable containers with nitrogen between the gas storage unit and laboratories at IBM must be performed by the Teknisk fellesavdeling.

We would like to remind you that all accidents and near-accidents must be reported to the Health, Safety and Environment (HSE) Division. Forms are available in the HSE Handbook or by contacting your immediate supervisor, safety delegate or the HSE Division.


General rules

Gas cylinders and gas tanks with liquid nitrogen should only be handled and used by qualified personnel with required training at IBM.

Do not use gas cylinders until you are absolutely sure what the contents are and you know the features and hazards of the gas. Important safety information is given on the label on the cylinder and the MSDS must be available to the user. Cylinders or a battery of cylinders that are leaking or have signs of mechanical damage or fire damage must not be used.

All accidents and incidents must be reported to the Institute management and Safety supervisor. The form is found in the Safety Manual, if needed the Safety supervisor can assist.

Protection and Security

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Gas cylinders must be secured in accordance with applicable rules. The gas cylinders have to be secured with a wall mounted bracket with either a strap or chain. The protective cap should not be removed until the bottle is at the site of use and secured against falling.

Rooms containing gas cylinders should have warning signs and information on the door:

  • Type of gas used
  • Number of bottles
  • Contact Person

The sign should be removed / covered when the gas cylinders are moved. Safety Data Sheets for the gases should always be available, see chemical registry Workplace safety.

For your own safety, wear suitable protective equipment under transportation and use of gas (especially important for the use of nitrogen). If liquid nitrogen is spilled on bare skin, do not rub the wound site but use lukewarm water. Always seek a doctor / emergency facility when deeper frost or tissue damage has occurred.

If there is a fire make sure that the taps on gas cylinders, gas tanks for nitrogen and central gas are shut before evacuation.

Transport and handling

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All transportation of gas cylinders and movable containers with nitrogen between the gas storage unit and laboratories at IBM must be performed by the Teknisk fellesavdeling.

Remove the pressure reducer and manometers during transportation. Protective cover and eventual blind nut should be fitted.

The transportation must be carried out using a special trolley with a chain to secure the gas cylinder. Only the freight elevator east in the BB-building can be used. Due to risk of suffocation by accident, gas cylinders and nitrogen containers MUST be transported alone in the elevator. The transportation process requires two persons, one sending the elevator up or down and a second person who retrieves the gas trolley / transport container in the appropriate floor.

Transportation of liquid nitrogen must be performed using moveable containers belonging to the transportation unit. Gas cylinders that are not in use for a minimum of two weeks must be stored in explosion proof rooms. They shall be transported to the main storage unit in the 1st floor or to the storage of gas cylinders in the 7th floor (grey zone). Gas cylinders must not be kept in stairs or corridors. Empty gas cylinders (minimum residual pressure 1.5-2 Bar) must be returned to the main storage unit on the 1st floor.

Liquid nitrogen

  1. Liquid nitrogen (-196 °C) can cause serious injury.
    • Frozen pipes can explode during defrosting and, among other things, cause injury to the eyes and result in blindness.
    • On contact with skin, liquid nitrogen can cause frost injuries which can develop into second or third-degree burns.
    • A lack of oxygen can arise when nitrogen evaporates in enclosed/airtight spaces (lifts, closed cars). Remember that 1 litre of liquid nitrogen expands to 700 l of nitrogen gas. Because nitrogen is heavier than oxygen, it would be particularly dangerous if you were to lose consciousness and fall to the floor. It is therefore necessary to take some precautions when working with and transporting nitrogen.
  2. Precautions / Instructions
    • Never fetch nitrogen alone. Use protective equipment such as a face mask, special gloves, overalls and appropriate shoes. The person who fills the nitrogen must follow the instructions posted in the filling area.
    • If you are using big containers, these must have lockable wheels and must be secured with straps during loading and transport. If you are using a lift, it must be empty (in such cases, the container must have a warning label so that other people do not enter the lift).
    • You must ensure that you have a suitable container, preferably with handles, when you are to transport small amounts of liquid nitrogen from one lab to another. Do not carry a styrofoam box half-full of nitrogen close to your body – use a trolley instead.
    • If you are transporting nitrogen by car, you must drive with the window open.
    • When freezing material in liquid nitrogen, you must always use test tubes that are designed for this purpose. Use gloves designed for use with nitrogen and a face mask!
    • If an accident occurs and you get liquid nitrogen on your bare skin, you MUST NOT RUB the wound but apply LUKEWARM water instead.
    • Always seek medical attention in the case of deep frost or tissue injuries.

Handling of gas

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Caution and respect are key words when handling gas cylinders.

  • Gas cylinders must not be thrown, tipped over or exposed to any impacts.
  • Gas cylinders must not be lifted or towed by the valve cap.
  • Never use grease or oil on oxygen equipment.
  • Smoking and open flames are prohibited when handling gas cylinders.

Use of compressed gas

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The use of compressed gas means that the gas in a desired amount is transferred from high pressure in individual bottles, or batteries of bottles, to a lower operating pressure in a distribution system.

All use of gas takes place at a much lower pressure than the pressure in a filled gas cylinder. For safety reasons a pressure regulator (reducing valve) connected to the cylinder valve is important. This pressure regulator shows both the bottle pressure and the working pressure from the regulator.

All use of gas takes place at a much lower pressure than the pressure in a filled gas cylinder. For safety reasons a pressure regulator (reducing valve) connected to the cylinder valve is important. This pressure regulator shows both the bottle pressure and the working pressure from the regulator.

Depending on the application, one or more of the following components is included in the distribution system:

Flame arresters to prevent backfire of burning gas
Pressure gauge for regulation in the system
Filter to prevent particles from contaminating sensitive apparatus
Flow-meter for measurement of gas flow
Check valve to prevent gas from going in the opposite direction
Pressure Relief Option to the open air or safe place

Before a distribution system is used for the first time, or after revision or replacement, the pressure and leakage must be tested. This is done by hydraulic or pneumatic pressure testing as specified in Section 13 TBK 5 "General Rules for Piping." Pneumatic pressure test can be performed with the appropriate gas as long as it is not toxic or flammable. In this case, an inert gas is used. In a distribution system for acetylene the user pressure may not exceed 1 Bar. Assuming a diameter not exceeding 25 mm the test pressure is 1.5 times the working pressure. Safe use of gas requires use of equipment in perfect condition and is suitable for the relevant gas and area of usage.

Pressure regulator

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  • Open the gas supply

Check that the pressure control valve is closed by turning the adjustment screw (2) counterclockwise until it is fully open.

Cylinder valve (1) can now be opened slowly and carefully.

Never use a hammer, pipe wrench or similar tool on the pressure regulator. Do not stand in front of the manometers when the cylinder valve is opened.

When the valve is fully open, check if the connection is tight. Continue opening the pressure to the regulator by turning the adjustment screw (2) clockwise and set the regulator to the desired pressure.

Finally open the outlet valve (3).

  • Close the gas supply

When the system is not in use make sure there is no pressure in the pressure regulator.

First close the bottle valve (1), when the pressure has been released and the manometer shows zero, turn the adjustment screw (2) counterclockwise until it runs freely and finally close the outlet valve (3).

Some more details on gas cylinder safety

Hazards

  • Flammable gases

A number of common gases ignite easily and burn releasing a lot of heat. In general, one should always follow the instructions for handling gas carefully.

The gases acetylene, MAPP, propane and hydrogen (H2) are extremely flammable and extra care should be taken.


  • Suffocation

If the content of oxygen in the air is reduced to half, we will pass out after a short time and suffocate. A number of fatal accidents have occurred in tanks, piping, vessels and other confined spaces due to oxygen deficiency.

In general, all gases that seep into a confined space, except for oxygen, will cause a risk for suffocation, especially if ventilation is poor as well.

Always check the oxygen content before and during entering a confined space. The oxygen content must be 21%. Lower oxygen levels require action. There will not be any notification of oxygen deficiency unless you measure the oxygen content!

NOTE: One cannot smell welding gases, nitrogen and other inert gases.

Gas under pressure

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The pressure in a gas cylinder is very dependent on the temperature.

Concerning the importance of temperature and gas, it is necessary to classify the different gases:

  • Compressed gas
  • Compressed and liquefied gas
  • Gas solved under pressure


The pressure in a gas cylinder will always depend on the temperature. It will rise and fall depending on the temperature. It is not only the properties of the gas that represent a hazard. A gas that is stored in a gas cylinder has a higher pressure than normal atmospheric pressure. In a 50 liter cylinder where the surface of the wall is approximately 1 m2 and normal filling pressure of 200 Bar will give a combined force of 2,000 tons against the bottle wall. An empty bottle with a residual pressure of 2 Bar will have a force equivalent to 20 tons against the bottle wall.











Compressed gas

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These gases are constantly in gaseous form in the bottle. For all such gases the pressure will increase equally and uniformly with rising temperature. If the bottle is kept at normal temperature it is possible to estimate the gas pressure in the bottle. Multiplying the bottle volume in liters with the pressure in Bar will give the amount of gas in litres.

Compressed and liquefied gas

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These gases are partially condensed into liquid inside the cylinder. This means that the lower part is filled with fluid and the upper part is filled with gas. As long as the temperature remains constant the pressure will be constant, regardless of how much of the bottle volume is occupied by gas or liquid.


Gas dissolved under pressure

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Acetylene is an unstable gas and cannot be filled directly into an empty gas bottle because of risk of explosion. The acetylene content can only be estimated by weighing the bottle and subtracting the tare weight, same as for liquefied gas.



Labelling and important gases

All gas cylinders must have labels indicating which gas or gas mixture it contains. The labelling should also specify the specific hazards of the gas, as well as providing information about simple precautions against these hazards.

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The bottle is stamped/marked (according to EN 1089-1):

  1. Manufacturer's name
  2. Production number / production year
  3. Pressure in Bar
  4. Production Control unit's label
  5. Date of latest revision (month / year)
  6. Controllers stamp
  7. Name of the gas
  8. Tare weight in kg.
  9. Volume in litres
  10. Bottle owner’s name and serial number
  11. Filling pressure
    • Filling pressure in bar of compressed gases
    • Fill weight in kg. for liquefied gases

Stamped label must not be removed or made illegible.


Packaging of compressed gas

Compressed gas is usually supplied and stored in cylinders of carbon steel, stainless steel or light metal alloys with capacity up to 150 litre. For certain applications, multiple gas cylinders can be connected to a battery that can be used as a transport device.

For compressed gases the maximum permitted pressure varies from 200 to 300 Bar. Condensed gases are filled to the maximum allowable weight per volume.

The gas cylinders are manufactured according to established rules to ensure quality. The gas supplier`s responsibility is periodical inspection and testing of properly equipped and marked gas cylinders.

The users are responsible for proper handling of the gas cylinders and for reporting irregularities to the gas supplier.


Some important gases

Argon
Nitrogen
Carbon dioxide
Ammonia
Hydrogen
Oxygen
MAPP
Acetylene
  • Argon and Nitrogen
    • Both of these are supplied as compressed gas and they are neither toxic nor flammable.
  • Carbon dioxide
    • Carbon dioxide (CO2) is usually supplied in gas cylinders, the gas is compressed and condensed. The gas is not flammable, on the contrary CO2 is used as a fire extinguishant.
  • Ammonia
    • Like CO2 ammonia is compressed and condensed in gas cylinders. Ammonia has a strong and unpleasant odor which will be detected before the concentration becomes dangerous.
  • Hydrogen
    • Hydrogen is supplied as a compressed gas. It is not toxic, but highly flammable and easily ignited. It burns with an almost invisible flame which can be difficult to detect. Hydrogen is the lightest of all gases.
  • Oxygen
    • Delivered in gas cylinders oxygen is compressed, colorless and odorless. Without being flammable oxygen is nevertheless in a unique position in terms of ignition and fire. The gas is heavier than air which normally contains 21 volume percent oxygen.
    • Just by increasing the oxygen content by 25 volume percent, there is an increased flammability risk, for example, during work. Pure oxygen when exposed to a variety burns of metals and other materials that do not normally ignite in air. The danger for ignition is particularly high in contact with lubricants such as oil, grease or mechanical seal materials.
    • Special precautions when using oxygen:
      • Use only components (pressure regulators, pressure gauges, fittings etc.) free of oil and grease and specifically designed and labeled for use with oxygen. Do not use the same components for other gases.
      • Valves that separate areas of high and low pressure (e.g. cylinder valves) should be opened gradually and gently after verifying that no contamination is present.
      • Use only gaskets, sealing and lubricants specifically approved for oxygen.
      • Do not use working clothes or tools, which are contaminated with oil or grease.
      • Never use oxygen instead of air, for example, when using compressed air driven tools.
      • If leakage of oxygen occurs, ensure adequate ventilation. Clothing should be aired thoroughly in fresh air.
      • Use of oxygen added odor (Oxysafe) reduces risk of leaks or spills because it is easily detected.
  • MAPP
    • MAPP is a compressed and condensed gas mixture with a higher calorific value per m3 than acetylene. MAPP is therefore particularly suitable as a fuel gas.
    • MAPP has also clear safety benefits such as no decomposition, less chance for backfire and a more narrow flammability range.
  • Acetylene
    • Acetylene is an unstable gas and special precautions have to be taken for storage under pressure in gas cylinders. External factors such as heating or backfire of burning gas through the cylinder valve may initiate a fission inthe bottle. If the fission is not detected and stopped, the temperature inside the cylinder may rise so it explodes.
    • The signs of fission are local heating of the cylinder or that the gas contains soot.
    • If this is observed proceed as follows:
      1. Close the cylinder valve and cool the cylinder by flushing with water from a secure place.
      2. Continue flushing until no more water evaporates from the cylinder when the flushing is stopped for a time, but keep the bottle cool and wet.
      3. The cylinder must not be used again and moved to a safe location.
      4. Check that the bottle stays cool for at least 24 hours to make sure that the fission does not recur.
      5. The operating pressures for acetylene should not be above 1 Bar because of risk of decomposition with increasing temperature and pressure.
    • In the same way as hydrogen gas, acetylene has a wide flammability range when mixed with air.

Further reading

  • ”Forskrift om håndtering av brannfarlig, reaksjonsfarlig og trykksattt stoff samt utstyr og anlegg som benyttes ved håndteringen”, DSB 08.06.2009.
  • Information about gases and their properties at Yara Praxair their websites.
  • Safety sheet see chemical registry, Workplace safety.