University of Leeds, School of Chemistry Approved Protocol
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University of Leeds, School of Chemistry Approved Protocol
The School of Chemistry Safety Committee have approved the following protocol for the named School operation or procedure. This task must be carried out in line with this protocol. If you believe that this protocol is unsuitable for the circumstances in your laboratory or area of work discuss this procedure with your supervisor or line manager and the appropriate Safety Advisor. Any modified operating procedures must be documented, approved and signed by your supervisor or line manager before they are undertaken1
University of Leeds, School of Chemistry Approved Protocol
Protocol for the operation of Inert Atmosphere Glove Boxes
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University of Leeds, School of Chemistry Approved Protocol
Main Hazards
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University of Leeds, School of Chemistry Approved Protocol
(1) Chemical hazard associated with the inert atmosphere gas, which is usually nitrogen or argon.
(2) Explosion hazard from too high a pressure of gas in the box, arising from a jammed solenoid valve.
(3) Cuts from flying glass associated with (2).
(4) Potential fire hazard, arising from contact of any pyrophoric materials stored inside the glove box with adventitious air or moisture associated with incorrect operation or maintenance of the glovebox, including (2).
(5) Release of toxic, irritant or flammable substances stored within the glovebox, associated with (2).
(6) Electrical shock hazard from electrical components (vacuum pump, plus optional oxygen meter, moisture meter, balance, refrigerator etc.).
(7) Explosion and chemical hazards from a hydrogen/nitrogen gas mix used, on an occasional basis, to regenerate the glove box drying train.
NOTE If the solenoid valves are old or poorly maintained, there is a small risk that these might jam open (point (2)). If this occurs, the atmosphere pressure inside the box will rise uncontrollably. This can be prevented, and the box made safe, by closing off the inert gas inlet valve. If that is not possible, retreat to a safe place. The gloves will eventually puncture explosively as the pressure builds up, which will then give rise to chemical and fire hazards associated with exposure of any pyrophoric materials stored within the box to air (points (4) and (5)). These should be dealt with appropriately, depending on the contents of the glove box.
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University of Leeds, School of Chemistry Approved Protocol
Key Safety Procedures
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University of Leeds, School of Chemistry Approved Protocol
Ensure COSHH and Risk assessment for the atmosphere gas inside the glove box, and for all chemicals already inside the glove box, have been performed. Ensure that COSHH and Risk assessment has been performed for the operation of any vacuum pumps and associated oil. Wear safety spectacles at all times. Be careful not to over-pressurise the box. Use the access ports to insert or remove items to or from the glove box, according to the following protocol.
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University of Leeds, School of Chemistry Approved Protocol
General Comments
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University of Leeds, School of Chemistry Approved Protocol
1. IF YOU HAVE NOT USED A PARTICULAR GLOVE BOX BEFORE, IT IS ESSENTIAL THAT YOU CONSULT A PERSON RESPONSIBLE FOR THAT GLOVE BOX BEFORE ATTEMPTING TO USE IT. In particular, it is important to determine what types of material can be stored within the glove box; and, what the detailed protocol is for bring items into and out of that glove box.
2. Ensure that the inert gas cylinder (if used) is not empty.
3. Ensure that the vacuum pump is turned on. Check the level of oil inside the pump, that it is clean, and that the exhaust is connected to the extraction system. Diffusion pumps should be fitted with flow-switches with fail-safe electrical shut-off.
4. Check that PAT testing of the pump, of the oxygen and moisture meters (if fitted), and of any electrical devices inside the box (e.g. balance, refrigerator etc.), is up to date.
5. Ensure that the gloves are in good condition, with no holes, and that they are tightly sealed onto the body of the glove box.
6. Ensure that there is a positive pressure of inert gas inside the box, and that this is within safe limits. If necessary, consult with a responsible person to find out what these limits are. HINT If the internal atmosphere is under a negative pressure, the gloves will be sucked into the box. If there is a positive pressure, the gloves will be standing proud of the box.
7. Ensure that the atmosphere inside the glove box is up to standard, using oxygen or moisture meters (if fitted) or, alternatively, appropriate chemical indicators. The allowable levels of oxygen and water will vary between glove boxes, depending on the model of glove box used and/or the substances stored inside. If required, advice should be sought from a responsible person regarding acceptable levels of oxygen and water for the glove box concerned. There are specific procedures to be followed for regenerating the atmosphere within the glove box (see below).
8. The glove box should be in a well-ventilated area.
9. If ANY pyrophoric substances are stored within the glove box, then a carbon dioxide fire extinguisher should be stationed close by, in case of accidental release of these pyrophoric materials.
10. Care must be taken when handling materials inside the glove box, particularly to avoid puncturing the gloves.
11. It is common practise to wear cotton, or disposable latex, gloves while one’s hands and arms are inside the gloves, to minimise the build up of sweat.
12. The use of mercury diffusion pumps is not recommended. Replace with oil diffusion pumps.
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University of Leeds, School of Chemistry Approved Protocol
Detailed Instructions for Use
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University of Leeds, School of Chemistry Approved Protocol
Bringing objects into the glove box:
1. Make sure you are wearing safety spectacles.
2. Make sure that the inner door of the port is closed and properly sealed, and that the port is not under vacuum.
3. Open the outer door of the port, and insert the object(s) to be brought into the box. Do not overfill the port, or include sealed Schlenk tubes or other closed vessels unless these are under vacuum (danger of explosion when the port is placed under vacuum).
4. Close and seal the outer door of the port.
5. Sign the log book (if used), to record that you are placing the port under vacuum.
6. Open the valve to the vacuum pump on the outside of the port, to evacuate the inside of the port. After a set period of time, close this valve. Then, open the valve to the inert gas cylinder to refill the port with the inert atmosphere. If necessary, consult a responsible person to determine the precise protocol to be followed for purging the port, which can vary between individual glove boxes. A typical cycle might be to evacuate the port under vacuum for 30 minutes, before refilling with the inert atmosphere.
7. Insert hands and arms into gloves, and remove interior seals (if fitted).
8. Remove inner door of the port, and carefully remove the item(s) from the port.
9. Replace and seal the inner door of the port.
10. Sign the log book (if used), to show that you have finished using the glove box.
Bringing objects out of the glove box:
1. Make sure you are wearing safety spectacles.
2. Determine whether the port is already under an inert atmosphere. If so, go to step (6). If not, proceed through steps (3)-(5).
3. Make sure that both the inner and outer doors of the port are closed and properly sealed.
4. Sign the log book (if used), to record that you are placing the port under vacuum.
5. Open the valve to the vacuum pump on the outside of the port, to place the inside of the port under vacuum. After a set period of time, close this valve. Then, open the valve to the inert gas cylinder to refill the port with the inert atmosphere. If necessary, consult a responsible person to determine the precise protocol to be followed for purging the port, which can vary between individual glove boxes. A typical cycle might be to evacuate the port under vacuum for 30 minutes, before refilling with the inert atmosphere.
6. Insert hands and arms into gloves, and remove interior seals (if fitted).
7. Open the inner door of the port, and insert the object(s) to be brought out of the box. Do not overfill the port, or include any sealed vessels (danger of explosion when the port is placed under vacuum).
8. Close and seal the inner door of the port.
9. Replace interior seals of the gloves (if fitted) and remove hands and arms into gloves.
10. Remove outer door of the port, and carefully remove the item(s) from the port.
11. Replace and seal the outer door of the port.
12. Sign the log book (if used), to show that you have finished using the glove box.
NOTE: Many modern glove boxes fill their ports with inert gas taken directly from the interior of the glove box, rather than a separate valve. If this is the case, it is vital not to fill the port with inert gas before the evacuation cycle is complete (step (4)). So if, for example, you have forgotten to put an item into the port before evacuating, you MUST wait the prescribed period of time before opening the inner door of the box to add the new item.
Regenerating the catalyst and atmosphere inside the glove box:
This is a maintenance procedure that must be performed at regular intervals, to service the gas drying train within the atmospheric circulation system. It can also be carried out on an exceptional basis, if the inert atmosphere within the box has become contaminated with too high a level of oxygen or water. The drying train typically contains one or more of each of these components: a set of molecular sieves, to remove water from the gas; and a catalyst that scrubs oxygen from the gas. A typical procedure might be as follows.
1. The drying train is sealed off from the rest of the atmosphere circulation system.
2. The drying train is heated strongly.
3. The drying train is placed under vacuum.
4. The drying train is purged with a hydrogen/nitrogen mixture (typically 5% hydrogen) for 2-3 hours. Water is collected from the exhaust gases.
5. Steps (3), (4) and (3) are repeated in that order.
6. While still under vacuum, the drying train is cooled.
7. The drying train is reconnected to the circulation system.
The precise sequence of events to be followed varies between different models of glove box. A responsible person must be consulted to determine the appropriate procedure, before this is attempted.
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University of Leeds, School of Chemistry Approved Protocol
Emergency Procedures
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University of Leeds, School of Chemistry Approved Protocol
If the atmosphere pressure inside the box will rises uncontrollably, this can be prevented, and the box made safe, by closing off the inert gas inlet valve. If that is not possible, retreat to a safe place. The gloves will eventually puncture explosively as the pressure builds up, which will then give rise to chemical and fire hazards associated with exposure of any pyrophoric materials stored within the box to air. These should be dealt with appropriately, depending on the contents of the glove box.
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University of Leeds, School of Chemistry Approved Protocol
Protocol written by: / Enter Name M HalcrowApproved by the Safety Committee: / Enter Date 1/2001
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University of Leeds, School of Chemistry Approved Protocol
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