September 06, reviewed 04/09/07, 27/05/09, 14/03/11 - PJS
Next review: March 2012.
RCS1 Cross-Faculty NMR Centre
STANDARD OPERATING PROCEDURE
THE TRANSPORT AND DISPENSING OF LIQUID NITROGEN INTO NMR
SPECTROMETER CRYOSTATS
This SOP is in TWO parts.
Part A covers the movement of Liquid Nitrogen dewars from the BOC fill area at the rear of
RCS1 (outside door DG17) to the Cross-faculty NMR Magnet chamber 014.
Part B covers the filling of NMR cryostats from a pressurized dewar.
Hazard statement:
Extreme low temperatures and asphyxiation
Cryogenic burns: Liquid nitrogen can cause cryogenic burns if the substance itself, or surfaces
which are or have been in contact with the substance (e.g. metal transfer hoses), come into contact
with the skin. Local pain may be felt as the skin cools, though intense pain can occur when cold
burns thaw and, if the area affected is large enough, the person may go into shock.
Frostbite: Continued exposure of unprotected flesh to cold atmospheres can result in frostbite.
There is usually sufficient warning by local pain whilst the freezing action is taking place.
Hypothermia: Low air temperatures arising from the proximity of liquefied gases can cause
hypothermia. Susceptibility is dependent upon temperature, exposure time and the individual
concerned (older people are more likely to succumb).
Risk of Asphyxiation: Nitrogen gas can displace Oxygen in the air. Normally air contains 78%
Nitrogen, 21 % Oxygen and 1 % argon gas. An atmosphere containing less than 18 % Oxygen is
potentially hazardous.
Combustion Hazard: Transfer lines and attachments at liquid nitrogen temperature can condense
liquid oxygen from the air. There is a potential combustion/explosion hazard if liquid oxygen is
dripped onto materials close to a source of ignition.
NB: A map of the RCS1 NMR suite is included at the end of this document
detailing room numbers, location of the BOC fill point and outdoor storage cage
and route of dewar transport from the fill point to the NMR chamber.
PART A: Transport of Liquid Nitrogen from the BOC fill point to magnet chamber
014
Personal protective equipment
Always wear personal protective equipment as described below. In particular always protect your eyes. One
set of relevant PPE is always kept in the magnet chamber 014, in a cupboard marked “PPE for cryogen fill”.
• Hands - non-absorbent insulated cryogloves must always be worn when handling anything that is or has been
in recent contact with liquid nitrogen. Cryogenic gloves are designed to be used in the vapour phase only and
should not be immersed into liquid nitrogen under any circumstances. They should be a loose fit to facilitate
easy removal. Gauntlet style gloves are not recommended as liquid can drip into them and become trapped
against the skin - sleeves should cover the ends of gloves or alternatively, a ribbed cuff style may be used.
• Face – during any dispensing procedure safety goggles must be worn.
• Body - a laboratory coat or overalls must be worn at all times. Open pockets and turn-ups where liquid could
collect should be avoided. Trouser bottoms should overlap boots or shoes for the same reason.
• Feet - sturdy shoes must be worn for handling liquid nitrogen vessel. Open toed shoes should not be worn
under any circumstances.
NITROGEN DEWARS MUST ONLY BE RCS1:
STORED
IN
THE
FOLLOWING ROOMS: 014 and outdoor storage cage. EMPTY
DESIGNATED AREAS:
dewars may be stored in the taped off area of corridor
013d.
The secure storage cage outside the CF-NMR Centre is kept locked. The key is available from the
Facility Manager Pete Simpson, x45336.
1.
Anyone transporting dewars must wear personal protective clothing, including lab coat and cryo
gloves.
2.
THE LARGE 180 LITRE DEWAR MUST ONLY BE TRANSPORTED BY TWO PEOPLE.
3.
Dewars should be brought in through the entrance DG17 door (i.e. main entrance in the white RCS1
NMR centre façade).
4.
Dewars should be transported along the corridor and through the double-door entrance to the NMR
chamber 014 (DG24).
5.
UNDER NO CIRCUMSTANCES SHOULD DEWARS BE TRANSPORTED THROUGH THE
COMPUTER SUITE 013.
Part B: Decanting from a pressurized storage dewar into the NMR
cryostats
You must wear protective clothing for this activity: laboratory coat, goggles and cryogloves.
1. Ensure the room is empty of personnel other than those involved in the nitrogen fill or experienced
spectrometer users.
2. Do not enter the magnet pit during nitrogen fill in case of splashing from the nitrogen exit port.
3. Ensure there is always someone else around during magnet fill, in case of accident.
4. Use only the metal transfer hoses and magnet fittings provided in room 014.
5. Keep magnetic tools away from the cryostats; tighten fittings outside the 5 Gauss stray field line
(white areas of floor) or (preferably) use the non-magnet spanners provided.
6. Make sure the hose is always pointed away from your face and body.
7. Open valves slowly.
8. Place a short length of rubber tubing on the magnet nitrogen exit port to direct venting away from
the magnet and towards the floor (this is always present on the 800 cryostat).
9. Vent a small amount of nitrogen through the transfer hose prior to attaching to the magnet in-fill
port to pre-cool the line.
10. Attachment of hoses to the magnet cryostat should be done with care to prevent rocking. If
excessive movement occurs stop until movement ceases and consider deflating the air-cushioned
legs.
11. Attach the transfer line to the magnet in-fill port with the supplied fittings (magnet specific).
12. Nitrogen should be transferred under a maximum pressure of 1 bar (12 psi).
13. Do not leave vessels unattended when filling.
14. The magnet cryostat is full when liquid nitrogen is ejected from the exit tube or can be monitored
on the 600 via the N2 meter.
15. If a valve freezes open and cannot be turned off, open the vent valve on the dewar to release
pressure and stop the nitrogen transfer. Allow the valve to defrost before closing (use the heatgun
if necessary).
16. At the end of a fill, defrost all fittings before attempting to remove them (use the heatgun or allow
to warm up). Ensure all fittings are dry.
Emergency Procedures:
In the event of a spillage or accidental release of a significant quantity of liquid nitrogen, enough to form a
small pool, the following procedures should be followed:
1. Evacuate the area. Deploy warning signs and safety barriers if necessary. Signs (in PPE
cupboard) and barriers are kept in the magnet chamber 014.
2. If the spillage is in the corridor outside of the magnet chamber, ventilate the area. Open the
external doors DG11 and DG27 to allow any spilt liquid to evaporate and the resultant gas to
disperse.
3. Try to stop the release if at all possible e.g. turn off valves, but only if it is safe to do so - always
wear protective clothing.
4. Do not re-enter area unless it is safe to do so. Wait until all the liquid nitrogen has evaporated and
at least 2 air changes have occurred. In the NMR chamber 014 this is after the oxygen monitoring
alarms have abated, or 12 minutes if the automated forced ventilation failed to activate. In the
corridor assume a minimum of 30 minutes.
5. Prevent liquid nitrogen from entering drains, basements, pits or any confined space where
accumulation may be dangerous.
A College safety guidance note: 015 Liquid Nitrogen – Storage, use and transportation within
College premises can be found on Spectrum. A hard copy is held in the NMR centre safety folder
which is located in the Computing Suite 013B.
http://www3.imperial.ac.uk/safety/subjects/gasesandcryo/lnguidance (link checked 14mar11)
First Aid Specifics
• Where inhalation has occurred, the victim (who may be unconscious) should be removed to a well
ventilated area.
• Rescuers should not put themselves at risk - a contaminated area should not be entered unless
considered safe.
• The person should be kept warm and rested whilst medical attention is obtained.
• If breathing has stopped then resuscitation should be commenced by a trained first aider.
• Where contact has occurred, the aim should be to slowly raise the temperature of the affected
area back to normal.
• For minor injuries, clothing should be loosened and the person made comfortable.
• Clothing should not be pulled away from burned or frozen skin.
• Douse the affected area with copious quantities of tepid water (40 C) for at least 15 minutes.
• For cold burns’ apply a sterile burn dressing to protect the injury until the person can be taken to
receive hospital treatment. If not available this can be improvised with a water-proof, lint-free
material, e.g. cling-film or plastic bag.
• Do not use a direct source of heat such as a radiator.
• Do not permit smoking or alcohol consumption.
• Do not give analgesics (e.g. paracetamol, aspirin).
• For major injuries apply first aid as far as is practicable and arrange for the victim to receive
medical attention.
Declarations
You must sign this form only after you have received training and when you are sure that you have read and
understood these instructions.
Name and e-mail
Pete Simpson,
[email protected]
Ernesto Cota,
[email protected]
Seb lambert
[email protected]
Chris Douse,
christopher.douse@googlemail
.com
Rhian Jones,
[email protected]
Read/
understood
SOP
Read/
understood
RA “Use of
cryogens in
CFNMR”
Attended Gas
safety course
2: Cryogenics
Signature
Date