This stage is not time critical.
Press Open to open the cryogen drawer and load a cryogen bowl. The bowl only fits on the location points one way round, so that the electrical contacts are correctly positioned.
The bowl is fitted with a liquid nitrogen level sensor. This is located in the side of the bowl. The measured level is displayed on the user interface.
IMPORTANT: Do not press on the LN2 level sensor cover (the slightly darker grey area on the bowl surround), it is delicate.
- Type in the grid button ID.
- Place the labelled autogrid button into the cryogen bowl and remove the lid of the button.
IMPORTANT: Don't forget to remove the lid, it will damage the tweezers otherwise. - If desired, the cryogen target temperature can be set between -160°C and -180°C. The default is -175°C.
- Next, press Load Cryogens.
Keep your hands clear of the drawer before and during closing operation, otherwise your hand may be trapped. Only one person should be interacting with the instrument when opening or closing the drawer.
Check that the Nitrogen Level and Ethane Temperature on the status panel are reading before adding LN2 and condensing ethane.
11.7.1 Load cryogens
SPT Labtech recommends that the ethane is condensed with the bowl located in the drawer.
Take care when handling the ethane condensing head once it has been chilled by liquid nitrogen.
Be aware of cryogen spillage risk to personnel operating in the vicinity of the instrument when filling cryogens.
An ethane condenser is supplied with the instrument. This is specifically designed to condense ethane into the ethane cup in the bowl assembly.
The condenser assembly consists of a:
- NPT1/4” connector, suitable for a standard ethane pressure regulator
- Handheld flow controller
- Condensing head
Preparation:
- Ensure that the ethane gas bottle is in a suitable position near the bowl to be filled
- Connect the condenser assembly to the pressure regulator
- Ensure that the pressure is set to 2 bar and open the valve
Ethane condensing
- Fill the bowl with liquid nitrogen and allow the ethane cup to cool completely: there is an audible hiss when it is ready.
- Ensure there is no LN2 remaining in the ethane cup.
- Place the ethane condensing head over the ethane cup, ensuring it is fully seat
- Ensure the ethane cup’s temperature is colder than -160°C
- Depress the button on the flow controller and observe the flow of ethane into the cup through the window in the top of the condenser head
- Liquid ethane should be seen to run out of the drip tube
- Continue until the ethane cup is filled to the base of the drip tube. Do not overfill.
- Release the push button to stop condensing ethane and remove the ethane condensing head from the cryogen bow, taking care not to contact any residual liquid ethane. Hold down the cryogen bowl during removal of condensing head.
- Top up the LN2 being careful not to overfill as this will cause the LN2 to flow into the ethane cup.
- Ensure that the ethane gas bottle supply valve is closed and the remaining gas released from the line.
- Allow the filling head to warm and dry before additional use.
- Press Continue. If this is not available, you have not entered the grid button ID.
Overfilling of liquid nitrogen can displace liquid ethane in the ethane cup, which can potentially cause serious cryogenic burns.
- Use appropriate PPE including but not limited to safety goggles when topping up liquid nitrogen in the cryogen bowl.
- Be aware of cryogen spillage risks to other personnel operating in the vicinity of the instrument when topping up liquid nitrogen.
11.7.1.I Condensing ethane while the cryogen bowl is not in the chameleon system
Follow the same steps as above, however, since the bowl is not in the system, the ethane temperature control heater will not be functional. Due to this, you must take particular care at the following points:
- Ensure that the ethane cup has no LN2 in it prior to placing the ethane condensing head over the ethane cup.
- Following this, ensure that the ethane cup is cold enough to begin condensing ethane.
- After condensing, the ethane will begin to freeze until the bowl has been installed onto the chameleon system where the heater will begin to regulate the temperature. You must take care not to allow the ethane to completely freeze prior to installation of the cryogen bowl on the chameleon system.
The area of foam above the LN2 level sensor is fragile and care should be taken not to pick up the cryogen bowl by this area or to press down onto this area during handling.
11.7.1.II Recovering from ethane overfilling
The ethane condensing head can become blocked or frozen to the ethane cup when overfilled. If this happens, recover as follows:
- Open the cryogen drawer fully.
- If needed, replace the flow controller on top of the bowl, ensuring the tubing does not wrap around the cryogen drawer
- Carefully pick up both using the wings at the bottom of the bowl.
- Once the cryogen bowl has been removed from the instrument, pour the cryogens out of the bowl and into a safe container.
- The ethane condensing head will need to partially warm up in order to be removed.
- Fully warm up and dry both the cryogen bowl and ethane condensing head prior to attempting to fill again. A blow drier can be used to speed this process after all liquid and gaseous ethane has been removed from the bowl and condensing head - do not use a heat gun!
Do not attempt to twist or pull the head off as this may cause damage to the cryogen bowl.
Blockage of ethane condensing head should never be cleared by increasing ethane gas pressure.
Over-pressure of ethane gas supply can result in gas fittings coming loose or free. This can result in a gas leak which gives an explosive atmosphere or asphyxiation hazard. Ethane gas supply should be shut off immediately should an ethane gas leak occur.
11.7.2 Remove the ethane condenser
After you press Continue, the Remove Ethane Condenser popup is shown.
After completion of ethane condensing, press Close Drawer to close the cryogen drawer.
Keep your hands clear of the drawer before and during closing operation, otherwise they might be trapped by the drawer. Only one person should be interacting with the instrument when opening or closing the drawer.
Do not close the cryogen drawer while the ethane condensing head is on the ethane cup. Doing so will damage the cryogen bowl and ethane condensing head.