Differences

This shows you the differences between two versions of the page.

--- thermcraft_tube_oven [2022/09/20 13:24] – [Setting up and starting the process] scholma
+++ thermcraft_tube_oven [2023/03/15 14:11] (current) – scholma
@@ Line 1: / Line 1: @@
-====== Description ======
+====== Tube oven annealing ======
 The tube oven has a temperature range of 50-1200 °C and can fit 1 inch diameter tubes. Temperature regulation is done by a Eurotherm 2404 controller.
 Three different process gasses can be connected, at the moment H2 and Ar are connected. Gas flow of each gas is controlled by a mass flow controller (MFC), mixing is possible.
 A dry vacuumpump is used to pump down the system, lowest pressure that can be achieved is roughly 1e-2mbar.
-A pressure control valve can be used to control either the flow or pressure in the tube. Most often the pressure control valve is operated in the fully open state to achieve a pressure as low as possible.
+A pressure control valve can be used to control either the flow or pressure in the tube. Most often the pressure control valve is operated in the fully open state to achieve a pressure as low as possible. Pressure can be controlled between 1e-2mbar and 100mbar.
 A Python program on the PC "hydrogen_annealing" can be used to set gas flows, the pressure set point and monitor and log the process.
@@ Line 37: / Line 37: @@
 If a process requires hydrogen we need to make sure it doesn't escape into the lab and the gas is mixed with nitrogen at the inlet of the pump to achieve a H2/N2 mixture below LEL.
-Flammable range of H2 in air is >4% (LEL) and <75%(UEL)
+Flammable range of H2 in air is >4% (LEL) and <75%(UEL).\\
+A flammable mixture of H2 and Air can be ignited on a hot surface if the temperature exceeds 500°C (in literature different values are mentioned, 500°C is chosen on the safe side).\\
+Hence when working with Hydrogen do not use processes above this temperature.
 There should be adequate ventilation in the lab, the window should be open.
@@ Line 95: / Line 98: @@
     * if you want to use a pressure setpoint you can set the pressure control valve to setpoint mode.
   * start pump
-  * open manual valves near MFCs of the gasses you would like to use
   * pressure should reach <1e-1mbar, if not: find and solve the leaks (typically the tube connectors)
@@ Line 103: / Line 105: @@
     * close safety cabinet
     * open manual valve behind the hydrogen MFC
-    * set nitrogen flow; nitrogen flow should be 100x hydrogen flow to dilute the gas mixture going into the pump.
+    * set nitrogen flow with the large round black needle valve on the wall; nitrogen flow should be >100x hydrogen flow setpoint to dilute the gas mixture going into the pump.
-    * make sure all safety interlocks are met; now you can open the hydrogen safety valve from the GUI
         * When first opening the valve you will have a small burst of flow, set a high nitrogen flow ~20000sccm when starting, later you can lower this to 100x hydrogen flow setpoint.
+    * make sure all safety interlocks are met; now you can open the hydrogen safety valve from the GUI
+    * open manual valves near MFCs of the gasses you would like to use
     * set other process parameters with the GUI
     * load temperature program from itools to the controller and run the program
+      * hold the run/hold button for a few seconds to stop the controller, if the controller is in hold state the program will not load.
@@ Line 116: / Line 121: @@
   * **If you used hydrogen:**
       * close hydrogen cylinder in the yellow safety cabinet with the angle key, keep hydrogen flow on
+      * wait **until hydrogen flow is almost zero**
+      * 'OPEN hydrogen MFC' from GUI
       * wait **until hydrogen flow is zero**, indicating the gasline is empty
-      * close pressure reducer behind the hydrogen cylinder
+      * close pressure reducer on the hydrogen cylinder
-      * close hydrogen safety valve from Python GUI
+      * close safety cabinet
+      * close hydrogen safety valve from the GUI
       * close green manual valve near hydrogen MFC
       * stop nitrogen flow
@@ Line 124: / Line 132: @@
       * turn off oven and wait for oven to cooldown to <50°C (can take a few hours since there is no active cooling)
       * switch off pump
-      * vent system with some nitrogen flow, or very carefully manually open a connector
+      * vent system
       * take out sample
-      * take tube out of the oven, and store it in the cabinet, properly labeled/marked
+      * take tube out of the oven, and store it in the cabinet, properly labeled
       * put blind flanges or aluminium foil on the open parts of the system and tube
@@ Line 134: / Line 142: @@
       * turn off oven and wait for oven to cooldown to <50°C (can take a few hours since there is no active cooling)
       * switch off pump
-      * vent system with some nitrogen flow, or very carefully manually open a connector
+      * vent system
       * take out sample
-      * take tube out of the oven, and store it in the cabinet, properly labeled/marked
+      * take tube out of the oven, and store it in the cabinet, properly labeled
       * put blind flanges or aluminium foil on the open parts of the system and tube
+===== Common problems =====
+=== PLC not connected ===
+The extra network card in the PC sometimes loses connection. Open the PC and unplug and plug back the network card. Restart the computer. Open the PLC program and try to connect to the PLC. LOGO!SoftComfort will recognize that the IPadres of the PLC is not in the same subnet mask and will ask to add this; acknowledge. Now you should have connection again.