Procedure for Filling 2 T Bruker Magnet with Nitrogen

Transcription

1 Procedure for Filling 2 T Bruker Magnet with Nitrogen Note: Nitrogen fills require 2 people to be present. Transfer of N2 from Reservoir to Dewar 1) Get keys from Phil s desk and open door to courtyard. [Note that when crash bars on double doors (into corridor) are opened they become permanently unlocked and need to be relocked with a key after filling]. 2) Get protective goggles from Phil s desk in workshop. 3) Get gloves from on top of He bottle in corridor (far end of corridor). 4) Move dewar from corridor outside into courtyard. 5) Open vent valve (Fig 1) to reduce pressure in dewar to close to zero. 6) Open and remove the leybold clamp around the neck of the dewar (Fig 1). 7) Slowly remove the valve unit and fill apparatus from the dewar. Also remove the O ring. Place the valve unit along with leybold clamp and O ring on the corridor floor (Fig 2). 8) Get transfer tube from the hook in the corridor and place this in the open dewar neck. Attach the other end to the filling connector on the Reservoir (Fig 3). The leybold clamp and O ring should be on this connector when not in use. 9) Pressurize the Reservoir by closing the vent valve (Fig 3) and opening the pressurizing valve (Fig 3). Note that if the vent valve has been accidentally left closed then the Reservoir can be at high pressure (40 psi). In such cases open the vent valve to reduce the pressure in the Reservoir. 10) When the pressure is up to approx 5 psi (to 10 psi), open the filling valve on the Reservoir (Fig 3) and N2 should flow. Note that if it is raining hard then it is best to shield the top of the dewar to avoid water getting into dewar. 11) Transfer takes approx. 20 mins. Wait until N2 spills over top of dewar. 12) When dewar is full (Fig 5) quickly close off the fill valve (Fig 3). 13) Return Reservoir to default state (pressure valve closed, vent valve open), and remove the filling tube from the reservoir. 14) Disconnect the transfer tube from the Reservoir, leaving the O ring and leybold clamp on the transfer tube. 15) Put plastic cover over the connector on Reservoir fill outlet. Close doors to Reservoir. 16) Replace filling tube on hook in corridor

2 17) Replace O ring on to collar of dewar. 18) Slowly insert valve unit and fill apparatus into the dewar (will get some boil off, so go slowly). 19) Re-attach the leybold clamp. Note that it will be necessary to re-tighten the clamp a few times as the dewar heats slightly. Transfer of N2 from Dewar to Magnet 1) Get log book from workshop. 2) Go into the equipment room and plug in the He/N2 monitoring unit into the wall. This is left unplugged by default to avoid the possibility of being left in Run mode when on (and hence increasing boil off). 3) Press the Manual button (Fig 6) to get the system to start sampling. 4) Take the initial readings for the N2 and record the value in the log book. 5) Open the back doors of the magnet room from inside the magnet room and wheel the dewar into the room and to the far side of the magnet. 6) Re-tighten the leybold clamp on the dewar to prevent spilling when filling. 7) Clamp the fill tube (dangling from the magnet side) to the fill valve on the dewar using the O ring and leybold clamp that can be found in the drawer near the magnet. Note that the leybold clamp is magnetic, so be careful. 8) Go up steps to top of magnet and remove the leybold clamp around the red vent hole. Note that the leybold clamp is magnetic, so be careful. 9) Place the leybold clamp, the red cover plate, and the O ring on top of the magnet for safe keeping (taking care to place the rubber bung on the leybold clamp so that it does not move in the field). 10) Re-tighten leybold clamp on dewar again to prevent spilling when filling! 11) Move the helium bottle in the corridor to the chained area near the 2T magnet room (but still in the corridor!). Note that the helium bottle and the stand are magnetic and must not be brought into the magnet room itself! 12) Chain the helium bottle to the wall for safety. 13) Run out the rubber hosing (Fig 7) into the magnet room (avoiding kinks) and attach the other end to the dewar pressurizer valve fitting. 14) Open the feeding valve on the dewar (Fig 1). Also open the vent valve (Fig 1).

3 15) Open the main (black) valve of the helium bottle (Fig 7). Turn the gold pressure valve clockwise to increase the pressure until it reads approx 5-6 psi (lbf/in2). 16) Tighten the leybold clamps if the dewar starts dripping. 17) While waiting for the magnet to fill (approx 15 mins) can switch the N2 monitor to fast sampling (Fig 6). Note that the system needs to be in Run mode (Fig 6). [Note that the Manual button is a bit sticky and can stick in the on position, never completing a reading! In which case give the button a jiggle.] 18) When the N2 reading gets to approx lower 90%s best to go back into the magnet room and wait for the magnet to show signs of being full. This can be ascertained by seeing a (subtle) spitting at the top of the N2 gas plume. 19) Turn off the fill valve on the dewar when the magnet is full. 20) Close the main (black) valve of the helium bottle. 21) Close the vent valve on the dewar and pull the rubber tube off the fitting (expect a mild pop). 22) Once rubber tube is removed from the dewar, re-open the vent valve and leave this open. 23) Note: can be useful to open and close the fill valve at this point to allow any liquid N2 in the transfer tube to drain into the Dewar. 24) Unscrew the leybold clamp on the dewar and remove the fill tube. Note that N2 liquid will pour onto the floor when the filling tube is detached. Best to stand on the ladder to do this to avoid N2 on the feet! 25) Put waste bin below end of filling tube to protect the floor from drips. 26) Replace the O ring and red blanking plate onto the vent hole on top of the magnet. Also re-attach leybold clamp around the red blanking plate to hold in place. 27) Coil up the rubber tubing and place on helium bottle. Turn the gold pressure valve on the helium bottle fully anti clockwise and replace the He gas bottle to the other end of the corridor. Make sure it is chained to the wall. 28) Replace dewar in corridor, taking care to avoid blocking the emergency exit from the magnet room. 29) Go into equipment room and record the final reading of the N2 fill in the log book. 30) Switch the N2 monitor back to slow sampling (Fig 6) and switch the unit to hold (Fig 6). 31) Turn the monitor off at the wall and take out the plug to avoid the unit being accidentally switched on between fills.

4 32) Return to magnet room and give a final tighten to the leybold clamp over the vent hole on top of the magnet. 33) Close magnet room doors and return log book to workshop. 34) Return gloves to top of He bottle in corridor. 35) Remember to lock all doors and return chains to corridor. Other Notes 1) BOC deliver N2 every other Monday and fill the N2 reservoir in the courtyard area. The usual driver is Steven Marsh ( , manager Tony Herbert ). Approximately 1000 litres is transferred each time BOC come. They need someone to let them in the gates of the courtyard (Sharon Dash). 2) The helium bottles last approx 1-2 months. There should always be one spare bottle kept outside in the courtyard, plus the one currently in use in the corridor. Replacement bottles are ordered from BOC via the University. [Liaise with Neserin Fleet in Biochem about changing the accounts info to Cardiovascular Medicine]. Current order is: Size L cylinder of helium gas. Grade A. Collect empty bottles as necessary. BOC Industrial National Accounting Centre PO Box 12 Priestley Rd Worsley Manchester MRC customer account number is Note that explicit instructions must be given for the bottle to be delivered to MRC MRS Unit, John Radcliffe Hospital. Otherwise the bottles have a habit of being delivered to the Industrial Block. In the event of a dire problem (no helium for some reason) Colin Hoey in the Industrial Block will often be able to loan out a bottle (to do an emergency fill, for example). 3) N2 is normally filled every two weeks, by which point the reading is typically in the range 60-65%. If the reading ever drops below 40-50% then the magnet should be filled as soon as possible. 4) He is normally filled every 3-4 weeks, when the reading gets to approx %. The danger level for He is likely to be anywhere below 50%, so avoid the He level going below 50%.

5 Figure 1 Vent valve and connection for He bottle pressurizer Transfer from N2 reservoir to dewar, and also from dewar to magnet auto vent valve up to 2 psi burst valve (needs replacing if it blows) Leybold clamp

6 Figure 2 O ring Leybold clamp

7 Transfer pressure (ideally 5-10 psi when filling, 0 otherwise). Level to indicate reservoir level (near red mark when full) Figure 3 Vent valve (normally open, but closed for dewar fills Valve and connector for filling dewar Only used by BOC. Leave closed Pressurize valve (open when pressurizing)

8 Figure 4 Transfer tube When transferring: Vent closed Fill valve open BOC valve closed Pressurizer open

9 Figure 5 Turn off fill valve when dewar spills over

10 Figure 6 Manual button to force sampling Slow/fast sampling setting Run/hold button Mains outlet

11 Figure 7 Gas pressure (ideally about 6 psi (lbf/in2) when filling magnet) Bottle level meter Main bottle valve Rubber pressurizer Tube to dewar Pressure valve (clockwise to increase pressure, anti-clockwise to reduce pressure