About the Quench Cooling AccessoryAbout the Quench Cooling Accessory
When you receive your Quench Cooling Accessory (QCA),
there will be some installation required, as well as certain guidelines
and safety issues to consider.
Select from the following topics for more information:
The QCA is designed to operate the Q Series™ DSC's below ambient temperatures using a manually-filled low cost alternative to the automated RCS and LNCS. The QCA consists of a thermal enclosure that surrounds the cell and a quench cooling can that is positioned over and around the cell and contacts the cooling flange below the cell. After loading the sample and reference pans, and replacing the two inner silver lids at ambient temperature, the quench cooling can is placed on the cell and a suitable coolant such as ice water, dry ice or liquid nitrogen is manually poured into the quench cooling can. When the desired lower temperature limit has been achieved, the quench cooling can is removed, the outermost lid is placed over the cell and the thermal method is started. Since active cooling is not present during experiments with the QCA, only T1 Heat Flow can be measured.
Temperature Range: –180°C to 550°C
Isothermal or slow heating ramp experiments above 400°C are not recommended. A “Flange Over Temperature Run Terminated” error message will be posted and the experiment will be terminated if the QDSC cell cooling flange temperature exceeds 400°C.
CAUTION: The operator of this instrument is advised that if the equipment is used in a manner not specified in the documentation, the protection provided by the equipment may be impaired.
You must unplug the instrument before doing any maintenance or repair work; voltages as high as 120/240 volts AC are present in this system.
WARNING: High voltages are present in this instrument. Maintenance and repair of internal parts must be performed only by TA Instruments or other qualified service personnel.
The QCA uses the cryogenic (low-temperature) agent, liquid nitrogen, for cooling. Because of its low temperature [-195°C (-319°F)], liquid nitrogen will burn the skin. When you work with liquid nitrogen, use the following precautions:
Liquid nitrogen boils rapidly when exposed to room temperature. Be certain that areas where liquid nitrogen is used are well ventilated to prevent displacement of oxygen in the air.
Wear goggles or a face shield, gloves large enough to be removed easily, and a rubber apron. For extra protection, wear high-topped, sturdy shoes, and leave your pant legs outside the tops.
Transfer the liquid slowly to prevent thermal shock to the equipment. Use containers that have satisfactory low-temperature properties. Ensure that closed containers have vents to relieve pressure.
The purity of liquid nitrogen decreases when exposed to air. If the liquid in a container has been open to the atmosphere for a prolonged period, analyze the remaining liquid before using it for any purpose where high oxygen content could be dangerous.
WARNING: Potential Asphyxiant. Liquid nitrogen can cause rapid suffocation without warning. Store and use in an area with adequate ventilation. Do not use the QCA in confined spaces. Do not enter confined spaces where nitrogen gas may be present unless the area is well ventilated.
The warning above applies to the use of liquid nitrogen. Oxygen depletion sensors are sometimes utilized where liquid nitrogen is in use.
The cell surfaces can be hot enough to burn the skin during a sample run. If you are conducting a subambient test on the DSC, cold could also cause injury. After running any type of experiment, you must allow the DSC cell to return to room temperature before you touch the inner cell surfaces.
CAUTION: Some surfaces of the QCA and DSC system may get extremely cold during the use of the QCA for cooling experiments. This presents a danger to exposed skin coming in contact with and adhering to the cold surfaces. We recommend that you do not remove the DSC lids when the instrument is at subambient temperatures to prevent moisture buildup in the system. However, if you do remove the lids or handle any cold surfaces, use forceps or gloves to prevent injury.
WARNING: Some of the DSC and QCA surfaces get cold during use of the QCA. The cold surfaces can cause condensation and, in some cases, frost to build up. This condensation may drip to the floor. Provisions to keep the floor dry should be made. A slipping hazard may result if the condensation is not cleaned up.
Isothermal or slow heating ramp experiments above 400°C are not recommended. A “Flange Over Temperature Run Terminated” error message will be posted and the experiment will be terminated if the QDSC cell cooling flange temperature exceeds 400°C.
The QCA quench cooling can is filled simply by manually
pouring a suitable coolant into the quench can. The coolant type used
will determine the lower temperature limit of the instrument. Observe
appropriate precautions when handling the coolant. Wear protective gloves
and safety glasses whenever handling cryogenic materials.
Once the QCA has been properly installed, follow the steps below to set up the instrument parameters.
Verify the correct cooler type (e.g., QCA) on the Tools/Instrument Preferences/Cooler Page of the DSC instrument control software.
Verify that a source of a dry nitrogen is connected to the base purge and Gas 1 ports on the back of the DSC instrument.
NOTE: Dry nitrogen is typically used for the QCA purge if the lowest temperature experienced during a run does not fall below –100°C. If the lower temperature limit is below –100°C, then helium must be used
Load the sample pan into the QDSC cell at or above room temperature.
Replace the two silver lids and then place the quench cooling can over the cell and lower it until it contacts the QCA cell cooling flange.
Add a suitable coolant into the quench cooling can until the desired initial temperature is achieved.
NOTE: For optimum baseline startup performance, isotherm the cell at the desired initial temperature with the quench cooler in place for 5 minutes before proceeding.
Remove the quench cooling can, quickly replace the outer lid and press the start button to begin the experiment.
At the end of the experiment, remove the lids and the sample from the QDSC cell. Replace the two inner silver lids and replace the quench cooling can.
Pour suitable coolant into the can until the cell temperature has returned to ambient temperature and the DSC/QCA is ready for the next experiment.