ZIRCONIA OXYGEN DETECTOR SERVICE MANUAL

Transcription

1 Service Manual ZIRCONIA OXYGEN DETECTOR SERVICE MANUAL TYPE: ZFK 3, 4, 7 TN5A08a-E

2 CONTENTS. PREFACE.... MEASUREMENT PRINCIPLE ADJUSTMENT Zero (Air) Adjustment Span Adjustment TROUBLE CHECK SHEET REPAIR...5 APPENDIX Wiring Diagram...6 Output characteristic table

3 . PREFACE This service manual explains repair and adjustment procedure of the Zirconia oxygen detector (ZFK 3, 4, 7) as a single unit. This manual is intended for use with the instruction manual (INZ-TN4ZFK3).. MEASUREMENT PRINCIPLE When yttria-stabilized zirconia ceramic is heated to hightemperature, only the oxygen ion becomes a movable solid electrolyte. In a zirconia element, the both sides of which are fitted with a platinum electrode, the electrode reactions in the following expressions occur for the oxygen concentrations P and P (P > P ). Electrode of P side O + 4e 0 (negative electrode) Electrode of P side 0 O + 4e (positive electrode) Filter P Measured gas Heater Electrode Insulating material Casing Zirconia element Fig. Detector structure Air P Output That is, the oxygen ion moves from the P side, where oxygen concentration is higher, to P side, where it is lower. This energy for moving the ion generates the electric force (E) indicated in the following expression. RT P E= n (O) (V) 4F P (O) P (O) =50.74 log (mv) (at 800 C) P (O ) E : Electric force P (O ) : Comparative (Air) oxygen concentration P (O ) : Oxygen concentration in the measured gas R : Gas constant (J mol - K - ) T : Absolute temperature F : Faraday constant (c mol - ) Coefficient is the value when the zircornia element is 750 C. (The sensor unit becomes 750 C with 800 C temperature control.) Therefore, unknown oxygen concentration P (O ) can be calculated from the electric force (E). --

4 3. ADJUSTMENT 3. Zero (Air) Adjustment ) Remove the 3 screws fixing the case cover. ) Feed the zero gas (Dry Air) through the sample gas inlet (on the lower side of the main unit) at the specified flow rate (0.5L /min). 3) After the voltage indication between the external terminals block (4) and (5) (the terminal block on the front panel 7P) is stabilized (feed zero gas for to 3 minutes), adjust the indication to 0 ± mv by VRZ on the printed board; ZFK 3, 4. For ZFK7, make sure that the indication is within ± 3mV. (No adjustment) 3. Span Adjustment ) Feed the span gas ( to % O /N ) at the specified flow rate. ) After the indication is stabilized, adjust it by VRS; ZFK 3, 4 Find the adjustment value using the following expression. E (Output:V) = 0.38 log /Px Px:Calibration gas concentration Example) In case of.% O /N E=0.38 log /. = v Make an adjustment with the VRs control so that V is obtained. Span VR VRS Zero VR VRZ 8 C4 0 R4 3 6 R C CN3 JAPAN VRS R7 R3 CN R R8 CN C3 R5 VRZ ZD ZD ZD4 ZD3 C TK4B569R SSR Fig. Printed board mounting diagram; ZFK 3, 4 For ZFK7, make sure that the indication is within 50 to 70mV when the gas with concentration of to % O /N is flowed. (Refer to Appendix Table.) (No adjustment) -3-

5 4. TROUBLE CHECK SHEET Phenomena Cause Checking methods (normal value) Protective measures Slow response Sensor element Change over between zero and span Replace deterioration gas and check if 60 seconds or longer Sample gas is not supplied or output is abnormal. Sensor outlet is clogged with crystallized sulfate mist. Output is unstable ZFK 3, 4 Disconnection of connector or poor contact Output is not deflected or remains the same. Output swings over. is needed for 90% response. Visually check for clogging of the outlet of the gas introduction case. Check if the connector is disconnected or move the connector part to check for the indication change. Remove the clogging. Replace with a gas introduction case (provided with gas outlet pot). Repair Disturbance noise Check if output is hunting. Eliminate noise. Sensor element Flow zero/span gas continuously for Replace the sensor deterioration 0 minutes or so, and observe the element. Fuse is blown out or power is not supplied. ZFK 3, 4 Disconnection of connector or poor contact Sensor is defective. Solid relay is defective. Printed board is defective. ZFK 3, 4 Constant voltage power supply is defective. Temperature controller is defective. Measuring range is exceeded. indication status. Check the fuse and the supply voltage specification. Check if the connector is disconnected or move the connector part to check for the indication change. Change over between zero and span gas and check for the indication change. Remove one end of the sensor terminal block (3) (4), and check for continuity. The range should be within to 3 Ω. When 4V DC is applied to the outer end (7) (8) (-), check if AC power between () () on the sensor element is turned on or off. (Check with a tester.) Change over between zero and span gas and check if the voltage value between the sensor outer end (5) (6) (+) indicates as shown below. Air: ± 3mV or lower to % O /N : 50 to 70mV. Check if the CN of the constant voltage power supply indicates ± 0.V. Check if the temperature indication is constant in a range of 800 ± 5 C. Flow measured gas after zero/span calibration. Replace the fuse or check the power supply. Repair Replace the sensor element. Replace the printed board or the solid relay. Replace the printed board or the solid relay or sensor element. Replace the constant voltage power supply. Replace the temperature controller. Review the specifications. -4-

6 5. REPAIR () Replacement of the sensor element ) Change the measuring gas line to the Air atmosphere and then turn off the power switch. When the device is operating, install an oxygen meter by bypass piping. Leave the device for about 30 minutes till it cools down. ) Remove the case cover (a). 3) Remove the 6 wires connected to the sensor terminal block (b) and the 3 M4 screws fixing the sensor (c). 4) Pull out the sensor (d) from the sensor case (e), and assemble the new sensor in reverse order of disassembly. After wiring is checked, perform energization and running to calibrate zero/span. When replacing the sensor element, also replace the packing with a new one. () Replacement of the sensor case ), ) Follow the procedure in Item (). 3) Remove the 3 M4 screws fixing the sensor (c). 4) Remove the screws fixing the sensor case from the bottom of the main unit, and remove the sensor case from the top. 5) Assemble a new sensor in reverse order of disassembly. (3) Replacement of the printed board (ZFK 3, 4) ), ) Follow the procedure in Item (). 3) Remove the 8 wires connected to the terminal block of the printed board and 3 screws fixing the printed board. 4) Assemble a new printed board in reverse order of disassembly. Perform energization and running to calibrate zero/span. (4) Replacement of the temperature controller ), ) Follow the procedure in Item (). 3) Remove the screws from the top of the temperature controller and the socket from the backside, and pull out the controller forward. 4) Assemble a new temperature controller in reverse order of disassembly. (5) Replacement of the constant voltage power supply (ZFK 3, 4) ), ) Follow the procedure in Item (). 3) Remove the 5 wires and the side fixing screws connected to the upper terminal block of the constant voltage power supply (g), and remove the constant voltage power supply. 4) Assemble a new constant voltage power supply in reverse order of disassembly. (a) Case cover (e) Sensor case (c) Screw (d) Sensor (b) Wiring (h) Printed board: ZFK 3, 4 Solid relay; ZFK 7. (f) Temperature controller (g) Constant voltage power supply: ZFK 3, 4 Not mounted on ZFK 7. Fig.3 Internal diagram of the oxygen analyzer -5-

7 R T ZFK3,4 APPENDIX Wiring Diagram SW Power supply F. 3A 85 to 65V AC Temperature controller 0 PXR to 65V AC 5 4 Approx. 8mV/800 C Sensor mv 85 to 65V AC Constant voltage power supply AC AC V 0 DC POWER SUPPLY IN DCV OUT SSR Heat R OUT IN ZFK CN CN3 Amp. P.C.B O Sensor 00 to 5V AC or 00 to 0V AC R T E Main power Temperature supply alarm Output 0 0 C Output Temperature alarm When the setting value (800 C) is exceeded by ±0 C R T ZFK7 SW *00 to 40V AC for CE compatible types Power supply F. 3A 85 to 65V AC Temperature controller 0 PXR SSR O Sensor 00 to 5V AC or 00 to 0V AC Heat R OUT ZFK 0 0 C Temperature alarm C Output -6-

8 APPENDIX TABLE ZFK 3, 4 Zirconia oxygen Analyzer Output characteristic table (ZFK 3, 4 output) %O OUTPUT (mv) %O OUTPUT (mv) E (OUTPUT : V) = 0.38 log /O % APPENDIX TABLE ZFK 3, 4, 7 Zirconia oxygen Analyzer Detector Output characteristic (internal sensor) %O OUTPUT (mv) %O OUTPUT (mv) E (OUTPUT : mv) = log /O % -7-

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