Vacuum System (VS) and Schlenk Line (SL) Safety

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Purpose This power point presentation offers a brief description on the safe handling, use and maintenance of VS and SL. The information provided can assist lab personnel with conducting a risk assessment, training and developing an SOP before using vacuum and SL system.

Disclaimer: This Safety Guidelines document/SOP was prepared exclusively for the use of University of Wisconsin-Madison students, staff and faculty engaged in activities related to their education, research, and/or employment. The content is intended to provide safe operational practices currently believed to represent best practices in the use and handling of chemicals involved in the process, and is not intended to replace hands-on practical training in the techniques described. It remains the responsibility of the Principal Investigator to assure that his/her co-workers are properly trained on hazard management, which may include adaptation contained within this document to meet specific needs to address specific hazards in a particular experiment in a laboratory. Reference to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not imply its endorsement or recommendation by University of Wisconsin-Madison.

Fig. 1

PUMPTRAPS

VACUUMMANIFOLD

Vacuum System (VS) and Schlenk Line (SL) Uses

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• VS & SL are effective and common devices in research laboratories for numerous chemical manipulations. Proper training and supervision are essential for working with this set-up in addition to proper knowledge of the chemicals involved. • In a laboratory set-up VS & SL are generally used for following manipulations:

1. Degassing 2. Chemical reactions 3. Drying ovens 4. Product drying 5. Filtration system 6. Quick glassware drying

To SL Vacuum port Heat Gun

For N2 Purge

Quick glassware dryingTo Schlenk line

DegassingFig. 2

Hazards Attributed to the VS and SL

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Explosions and chemical hazards are associated with VS and SL. Use of cryogenic liquids can cause cold burn. Glassware handling hazards (explosions and implosions) are also possible.

Fig. 3

VS and SL

Glassware handling

(emplosions)

Condensed gases/chemicals pump oil contaminations

(explosions/chemical reactions)

Heating closed diffusitionpump or reaction flask(explosions)

Manipulation specific(Explosions or runaway rexn.)

Cryogenic liquid use (cold burn)

Engineering Controls

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Because of the dangers of implosion and explosions associated to VS and SL, manipulations should be performed inside a properly functional chemical fume hood.

Fig. 4

Administrative Controls If possible, avoid working alone while conducting experiment with high hazardous materials using either a SL or VS. The buddy system provides added protection in the event of an emergency. Know the exact location of the eye wash station, safety shower and fire extinguishers in your lab before starting experiment.

Personal Protective Equipment Requirements

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Eye Protection Safety glasses or goggles should always be worn to protect the eyes from implosion and explosion. Body Protection A long-sleeved laboratory coat is recommended while working with SL system and vacuum system. If reactive chemicals are manipulated under vacuum, a flame resistant lab coat is recommended. Gloves Nitrile gloves are acceptable for manipulating maximum chemicals during SL & vacuum manipulations, however a proper hazard assessment is needed involving highly hazardous chemicals.

Nitrile Lab coatsFace shield Safety glasses

Fig. 5

Hazards and Personal Protective Equipment Requirements for Manipulating VS & SL

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REQUIRED PERSONNEL PROTECTIVE

EQUIPMENT (PPE) FOR SCHLENK LINE USE

HAZARDSCryogenic

LN2Explosions Implosions

Thermal gloves, safety glasses and lab coat

Safety shield (if horizontal opening sash are not available) and goggles in addition

to safety glasses and lab coat

Fume hood sash

PPE

Fig. 6

Safety Measures & Techniques: Vacuum System

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• Use cold traps (liquid nitrogen or dry ice traps) for protecting pumps from corrosive and flammable solvents and vent pump exhaust into an exhaust system. • Never use flexible tubes for venting vacuum pumps, to ensure that vacuum pump exhaust obstruction should not occur during operation. Also check exhaust pipe regularly for oil back suck (see below).

Continue

• Belt guards should be in place during vacuum pump operation.

PUMP

Oil blockage

To exhaust system

Vacuum

PUMP

To exhaust system

Vacuum

XFig. 7

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• Make sure the system is under vacuum while any part of manifold is under liquid nitrogen. Otherwise, oxygen could condense, which could result in a serious explosion. • Never run vacuum pumps near flammable and temperature sensitive chemicals. Avoid placing vacuum pumps inside closed cabinet to avoid the overheating. FIRE HAZARDS!

Fig. 8 • Vacuum pump oil contaminated with hazardous chemicals and flammable solvents should not be operated to circumvent the pump system damage.

OK

NEVER CLOSE THE CABINETDOOR

X

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Fig. 9 • Never store flammable and temperature sensitive chemicals near running vacuum pump

(fire hazards). • Check the trap after each manipulation for the solvent/water, and empty it, if the trap is completely filled. Never clog the bypass tubing while the line is on.

Liquid O2

X

O2

Safety Measures & Techniques: Vacuum System

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• Always inspect glassware and reaction set-up for any deep notching star cracks, or any cracking at all in the flasks before using under vacuum. Glassware should be replaced immediately if it is cracked. • Before working with SL system attached to a vacuum system, researchers must be fully aware with SL operation (valves, diffusion pump and cooling system). • If possible use plastic coated glassware or taped flasks for vacuum system to avoid injury from flying glass in case of an explosion. • The hood sash should be closed as much as possible during SL operation.

Taped Flask

Broken receiving flask

Vacuum Pump Maintenance: Oil Change

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• Regularly monitor the condition of the pump oil and filters. Pump used for conducting corrosive chemical manipulations are more prone to damage and require frequent oil change. • Use sight-glass to check the oil-level which should be between the Max and Min level marks on the groove of the sight-glass. • Frequent use of water samples and volatile compounds requires regular oil change. Pump oil contaminations with residual water and corrosive chemicals will damage pump quickly.

Vacuum Pump Maintenance: Oil Change

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Vacuum Pump Attached to a Vacuum Manifold

Isolate vacuum pump from vacuum lines (SL & any glass assembly)

Bring pump to atmospheric temperature and pressure

Drain the contaminated pump oil using bottomscrew

Refill the flushing oil into vacuum pump and run the pump for 5-10 minutes and

finally drain the flushing oil

If possible oil change should be conductedinside a chemical fume hood to avoid thechemical exposures from old pump oil

Slightly warm vacuum tubeto isolate from vacuum system safely

Collect pump oil into a seperate container for disposal purpose

Repeat this step untill drain flushing oil

is clean

Refill new pump oil

Remove connecting tube carefullyto avoid the glass manifold damage

Incline the pump to drain all of the

pump oil.

Fig. 10

Schlenk Line (SL):Turn on Process

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Fig. 11

Grease all Joints

Place on liquid nitrogen traps/Dewars

Close the vent and turn on pump

Turn on vacuum gauge

Turn on nitrogen valve

Use appropriate grease and do not apply in excess (Krytox,

Dow corning vacuum grease etc.)

Use proper PPE., Clamp Dewar properly

Close all release vents and turn on pump; if diffusion pump is included in the line, open the valve before heating the pump oil (never heat closed diffusion pump or it will explode)

Check for any leak in the system by using vacuum gauge and other appropriate tools

Schlenk Line Cold Trap Safety

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Fig. 12

Liquid O2

X

O2

Cloggedbypass tube

X

Liquid O2 (LO2) Condensation in Cold Trap: • Liquid nitrogen in an open Dewar presents no additional hazards beyond frost bite; however, liquid nitrogen condenses out air at liquid nitrogen temperature. • SL systems, including liquid nitrogen traps, should never be opened to the atmosphere until the trap is detached from the coolant. • LO2 is highly explosive in nature in the presence of organic compounds, including the grease used for the glass joints of SL. • LO2 is light blue in color, and can pose dangerous conditions if condensed into cold traps.

Schlenk Line Cold Trap Safety (Liquid Oxygen Condensation

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• Extreme care should be taken if liquid nitrogen is used for the trap, to avoid the condensation of oxygen from air. • Oxygen has a higher boiling point (-183 oC) than nitrogen (-196oC) and will condense out of the atmosphere and collect in a liquid-nitrogen cooled container open to the air. • If you ever see a deep blue color in a trap, seek assistance from experienced laboratory staff or Environmental, Health and Safety (EH&S). • If help is not available, keep the vacuum on the system to pump the trap, and slowly warm up the trap (e.g., leave the trap on but do not add more liquid nitrogen). • If you’re not sure that liquid oxygen has condensed in a cold trap, then shield the trap (with an explosion shield, closed hood window, etc.), post a sign indicating the danger, and allow the trap (vented to the atmosphere) to slowly warm to room temperature.

Aspiration of Biological Materials

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AB

HEPAfilter

Bleach

Overflow collection flask

Utilization of local or central vacuum systems for biological materials in laboratory can contaminate vacuum lines, pumps and laboratory equipment. Using vacuum line traps and filters can prevent infectious material from entering vacuum lines. Therefore, aspiration of culture media or other fluids with a suction or aspirator flask A should be connected to an overflow collection flask B containing a appropriate disinfectant. Connect the flasks to an inline filter followed with a HEPA filter designed to protect the vacuum system. The HEPA filter must be inspected and replaced if clogged or if liquid makes contact with the filter. Bleach is easily inactivated by sunlight, needs regular fresh solution preparation and is a corrosive solution to metals, membranes and skin.

Fig. 13

SL: Shut Down Process

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Disconnect vacuum gauge (if line is connected)

Shut down the vacuum pump and release the vacuum from line

Remove liquid nitrogen Dewars/traps ASAP, disconnect nitrogen supply

Open the air vent and remove the excess grease from joints, clean

the traps

Do not leave traps open in liquid nitrogen

Place the traps in a proper/designated place after transferring the liquid nitrogen in tank (do not use funnel for transfer, use proper PPE). The fume hood with a Schlenk line must be kept uncluttered before and after manipulations

.

If diffusion pump is used for vacuum, cool it down before shutting down the pump

Fig. 14

Managing Spills Involving Pump Oil & Reagents

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For small chemical spills inside chemical fume hood, use dry sand/lime, or other non-combustible material for covering the spill material, close the hood sash. If a spill occurs outside a fume hood and you are unable to handle the spill call immediately 911 and EH&S at 265-5000.

Disposal of Used Pump Oil and other Unwanted Materials

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Unused pump oil/used pump oil and solvents/reagents from vacuum/SL manipulationsUnwanted material disposal methods

containing:

Unused pump oillarge qty.

Keep in original containerfor disposal purpose

(do not mix with solvent carboy)

Used contaminated pump oil

Solvents from traps

Mix into a non-halogenated and halogenated solvent carboy based

on nature

Unused pump oilsmall qty. (5-10 mL)

Mix with solvent carboy(non-halogenated)

Use a plastic containerand label as USED PUMP OILfor disposal purpose

Reagents and reactive chemicals collected from traps

Collect into a seperate containerfor disposal purpose (LABEL AS UNWANTED-XYZ)

Fig. 15

References

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• Instructional manual, Edwards: www.edwardsvacuum.com

• Reactivity control using a Schlenk line, Journal of Chemical Health and Safety, 21 (3), 2014, 22.

• Stahl group , Chemistry , safety wiki page.

• Policy for the Use and Storage of Inert Cryogenic Liquids; http://www.ehs.wisc.edu/chem/CryogenicLiquidsPolicy.pdf

• Cryogenic liquids: The cold, hard truth: Chemical Health and Safety, 7(3), 2000, 38. • http://www.cdc.gov/hicpac/Disinfection_Sterilization/6_0disinfection.html • UIC, EH&S Office: Recommendations for protective vacuum systems.