March 2013 PAGE 1 of 5 T004.BioTector TOC Analyzer Pressure and Flow Test failure analysis Section 1: Pressure Test. Theory of operation. The Mass Flow Controller (MFC) in the BioTector is used to confirm that there is no leak in the BioTector. The pressure test operates as follows: 1. The normally open exhaust valve is energized closed. 2. The normally closed sample out valve is de-energized so that it remains closed. 3. The MFC is given a set point typically of 40 LPH. 4. The gas flows through the MFC, but because all the outlets from the reactor are sealed, after about 10 seconds, the flow through the MFC will start to fall. 5. If there are no leaks in the system, the flow through the MFC will eventually fall to < 1 LPH, as the pressure in the BioTector equalizes with the pressure on the oxygen regulator. The sections of the BioTector which are covered by the pressure test typically are: 1. Outlet of MFC. 2. Ozone generator. 3. Reactor. 4. Circulation pump. 5. ARS valve. 6. Sample out valve, MV5. 7. Cooler. 8. CO 2 analyser. 9. Ozone destructor. 10. Exhaust valve. See example system drawing below for details.
PAGE 2 of 5 Pressure Test Simulation. The pressure test can be simulated in the Simulate menu as follows: 1. Confirm that the feed oxygen pressure, from the oxygen cylinder or oxygen concentrator is <1.5bar. 2. Energize the sample out valve so that it is open. 3. Remove the plug from the sample out valve so that it closes. This is essential, as the safety interlocks in Process Simulate 1 will prevent you from simulating the pressure test. 4. Energize the exhaust valve so that it closes. 5. Give the MFC as setting of 40 LPH. CAUTION! The BioTector is now under pressure. Therefore it is possible that if there is a leak in the system some liquid (acid or base) may quickly leak out. Always ware safety glasses when working with acid and base. CAUTION! Do not allow the pressure to rise above 350 mbar. 6. In there are no leaks in the system, the flow through the MFC will drop to <1 LPH after about 30 seconds. 7. When the test is complete, or to vent the system at any time, replace the plug on the sample out valve.
PAGE 3 of 5 Possible causes of a pressure test failure. Fitting not tight on Reactor, ARS valve, Circulation pump, Cooler, CO 2 Analyser or Ozone Destructor. Leak in Reactor, ARS valve, Circulation pump, Cooler, CO 2 Analyser or Ozone Destructor. Exhaust or Sample Out valve passing. Damaged ARS valve. The simplest procedure for checking this is to fill the sample in and sample bypass lines before and after the ARS valve with water. If there is a leak in the ARS valve, bubbles should appear in the sample bypass line, during the simulation of the pressure test (see page 3). Piston on the heavy duty pump worn out. When the ceramic piston is worn, the pressure test will fail as the oxygen gas will flow up through the piston (between the ceramic piston and the ceramic liner) and out the water out port. If the water out tube is immersed in liquid, after a few minutes bubbles will be seen leaving the tube, during the simulation of the pressure test (see page 3). Leak in Viton or Kalrez tube in the Ozone Generator. Crack in the Ozone Generator. Faulty MFC, which permanently displays high readings. To test this, give the MFC a low setting, for example 5 LPH and see if the flow drops to this level. Try tapping the control valve lightly if the reading remains high. Fault with the oxygen regulator. If the outlet pressure on the regulator increases as the flow through the MFC drops, then the flow will fall to a certain level and remain constant as the pressure on the regulator increases above its 350mbar setting. When the pressure stops rising, then the flow on the MFC will fall again. Example: 1. The pressure test starts with a flow of 40 LPH, the regulator pressure being 350 mbar. 2. The flow on the MFC quickly drops to 6 LPH, with the regulator output pressure remaining at 350mbar. 3. The output pressure from the regulator now slowly increases, with the result that the flow on the MFC remains constant at 6 LPH. 4. When the output pressure on the regulator stops rising, the flow on the MFC falls again. However, if the flow on the MFC remains at 6 LPH for over 60 seconds, then the pressure test will fail. Confirm that the feed oxygen pressure, from the oxygen cylinder or oxygen concentrator is < 1.5bar.
PAGE 4 of 5 Section 2: Flow Test. Theory of operation. The Mass Flow Controller (MFC) in the BioTector is used to confirm that there is no blockage in the BioTector. The flow test is divided into two sections, and operates as follows: Section 1, MV1 Exhaust gas path. 1. The normally open exhaust valve is de-energized open 2. The sample out valve is de-energized closed. 3. The MFC is given a set point typically of 80 LPH. 4. The gas takes the flowing path: a. MFC. b. Ozone generator c. Reactor. d. Cooler. e. CO 2 analyser. f. Ozone destructor. g. Exhaust valve and exhaust tubing. 5. If there is no blockage in the system, then the flow will remain at 80 LPH. However, if there is a partial blockage in the system, then the gas flow will drop. If the flow is less that 72 LPH (typical setting), a LOW O2 FLOW - EX (LOW FLOW MV1) fault will be generated. Section 2, MV5 Sample out gas path. 1. The normally open exhaust valve is energized closed 2. The sample out valve is energized open. 3. The MFC is given a set point typically of 80 LPH. 4. The gas takes the flowing path: a. MFC. b. Ozone generator c. Reactor. d. Sample out valve and sample out tubing, including the cleaning cycle catch pot (if fitted). 5. If there is no blockage in the system, then the flow will remain at 80 LPH. However, if there is a partial blockage in the system, then the gas flow will drop. If the flow is less that 72 LPH (typical setting), a LOW O2 FLOW - SO (LOW FLOW MV5) fault will be generated. See the drawing on page 2 for details. Flow Test - Simulation. The flow test can be simulated in the Simulate menu as follows: 1. For the MV1 (exhaust valve) gas path, the sample out valve should be de-energized closed and the exhaust valve de-energized open. 2. For the MV5 (sample out valve) gas path, the sample out valve should be energized open and the exhaust valve energized closed. 3. Give the MFC a set point of 80 LPH, and wait at least 60s. The flow and set point should be the same if there are no blockages in the system.
PAGE 5 of 5 Possible causes of a flow warning. Oxygen inlet pressure low. Exhaust (MV1) or sample out (MV5) valves blocked. Tube in the BioTector or outside the BioTector blocked. Ozone inlet to the reactor blocked. Ozone destructor blocked. Possible material built up in the reactor. There may be a build-up of a sludge like material in the reactor. This can have an effect on the flow. If this is the case, the reactor / glass bead chamber should be cleaned, and if necessary, the glass beads should be replaced. Faulty MFC, which permanently displays low readings. To test this, open the tube at the outlet of the MFC, and give the MFC a high setting, for example 80 LPH, and confirm that the flow increases to this level.