Model OT-2 System OPERATING INSTRUCTIONS FOR Model OT-2 Oxygen Transmitter System DANGER HIGHLY TOXIC AND OR FLAMMABLE LIQUIDS OR GASES MAY BE PRESENT IN THIS MONITORING SYSTEM. PERSONAL PROTECTIVE EQUIPMENT MAY BE REQUIRED WHEN SERVICING THIS SYSTEM. ONLY AUTHORIZED PERSONNEL SHOULD CONDUCT MAINTENANCE AND/OR SERVICING. BEFORE CONDUCTING ANY MAINTENANCE OR SERVICING CONSULT WITH AUTHORIZED SUPERVISOR/ MANAGER.
Model OT-2 System Copyright © 1999 Teledyne Analytical Instruments All Rights Reserved. No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any other language or computer language in whole or in part, in any form or by any means, whether it be electronic, mechanical, magnetic, optical, manual, or otherwise, without the prior written consent of Teledyne Analytical Instruments, 16830 Chestnut Street, City of Industry, CA 917491580.
Model OT-2 System Table of Contents 1 Introduction 1.1 1.2 1.3 1.4 Overview ........................................................................ 1-1 Features .......................................................................... 1-1 Typical Applications ...................................................... 1-2 Operator Interface ....................................................... 1-3 2 Operational Theory 2.1 Introduction ...................................................................
Model OT-2 System Appendix Specifications ........................................................................ A-1 Recommended Spare Parts List .......................................... A-2 Drawing List ............................................................................ A-2 Material Safety Data Sheet .................................................
Model OT-2 System Introduction 1 Introduction 1.1 Overview The Teledyne Analytical Instruments Model OT-2 System is designed to accurately monitor the oxygen content in a wide variety of gases at the ppm level. The Trace Oxygen Transmitter is equipped with two oxygen analysis ranges, 0–10 ppm and 0– 100 ppm (0-100 ppm and 0-1000 ppm optional).
1 Introduction Model OT-2 System • Accurate (±2% of full scale at constant temperature on 100 ppm, or 1000 ppm scale; ±1 ppm on 0–10 ppm scale at constant temperature) • Insensitive to flow variations • Fast response and recovery • Long life, maintenance-free Micro-Fuel Cell oxygen sensor • Unaffected by reducing agents (HC's, CO, SO2, etc.
Model OT-2 System 1.4 Introduction 1 Operator Interface The OT-2 System is housed in a rugged metal NEMA-4 case with the display visible from the front and the controls accessible from inside the front door. See Figure 1-1. The front door has a clear Lexan window for viewing the sample system components and transmitter display.
1 Introduction 1-4 Model OT-2 System Teledyne Analytical Instruments
Model OT-2 System Operational Theory 2 Operational Theory 2.1 Introduction The OT-2 System is composed of three subsystems: 1. Micro-Fuel Cell Sensor 2. Electronic Signal Processing, Display and Control 3. Sample System The Micro-Fuel Cell is an electrochemical galvanic device that translates the amount of oxygen present in the sample into an electrical output. The electronic signal processing, display and control subsystem provides oxygen concentration information both visually and electronically.
2 Operational Theory Model OT-2 System 2.2 Micro-Fuel Cell Sensor 2.2.1 Principles of Operation The oxygen sensor used in the Model OT-2 System is a Microfuel Cell designed and manufactured by Analytical Instruments. It is a sealed plastic disposable electrochemical transducer. The key components of the Micro-Fuel Cell are a diffusion barrier in the form of a thin membrane, a cathode, an anode, and an electrolyte in which they are immersed.
Model OT-2 System Operational Theory 2 Refer to Figure 2-2, Cross Section of a Micro-Fuel Cell, which illustrates the following internal description. Figure 2-2. Cross Section of a Micro-Fuel Cell (not to scale) At the top end of the cell is a diffusion membrane of Teflon. Beneath the diffusion membrane lies the oxygen sensing element—the cathode. The anode provides the electrical driving force for the reduction of oxygen at the cathode.
2 Operational Theory Model OT-2 System 2.2.3 Electrochemical Reactions The sample gas diffuses through the Teflon membrane. For a sensor that employs KOH as electrolyte, oxygen in the sample gas is reduced on the surface of the cathode according to the following HALF REACTION: O2 + 2H2O + 4e– ® 4OH– (cathode) (Four electrons combine with one oxygen molecule—in the presence of water from the electrolyte—to produce four hydroxyl ions.
Model OT-2 System Operational Theory 2 2.2.4 The Effect of Pressure The Micro-Fuel Cell responds to the partial pressure of oxygen present inside the cell holder. By design, the total gas pressure inside the cell holder is kept approximately the same as the atmospheric pressure. As the atmospheric pressure changes, the partial pressure of oxygen in the cell holder will change accordingly. The impact due to changes in atmospheric pressure is usually limited to less than 3% of reading.
2 Operational Theory Model OT-2 System 2.2.5 Calibration Characteristics Given that the total pressure of the sample gas on the surface of the Micro-Fuel Cell input is constant, a convenient characteristic of the cell is that the current produced in an external circuit is directly proportional to the rate at which oxygen molecules reach the cathode, and this rate is directly proportional to the concentration of oxygen in the gaseous mixture.
Model OT-2 System 2.3 Operational Theory 2 Electronics and Signal Processing The OT-2 circuitry consists of three stages: an input stage, a temperature compensation/gain stage and an output stage. The input stage consists of a current to voltage converter producing a voltage signal that is proportional to the oxygen concentration as detected by the sensor. The temperature compensation stage contains circuitry that compensates for the temperature effects on the output current of the O2 cell.
2 Operational Theory 2.6 Model OT-2 System Sample System The system consists of a shut off valve, particulate filter, pressure regulator, scrubber, calibration selector valve, flow control valve, O2 transmitter and a sample flow meter and incorporates ¼ inch tube fittings for sample inlet and outlet connections at the side of the enclosure. H2S from the sample gas can diffuse into the Micro-Fuel Cell leading to the formation of lead sulphide with the anode material.
Model OT-2 System Operational Theory 2 Figure 2-5 Piping Layout Figure 2-5 is the Piping Layout of the sampling system. In the standard instrument, calibration gases (zero and span) are connected directly to the Span Gas In port by teeing to the port with appropriate valves. The sample gas is connected to the Sample Gas In port in the same manner as the Span Gas.
2 Operational Theory 2-10 Teledyne Analytical Instruments Model OT-2 System
Model OT-2 System Operation 3 Operation Operation of the Model OT-2 System involves installing the unit, making appropriate sample gas connections, and calibration. 3.1 Installation WARNING: Safe operation of the system requires the user to properly ground the system, install the wiring and power the transmitter. It is the user's responsibility to determine and install, should a safety barrier be required. Installation of the Model OT-2 System includes: 1. Unpacking 2. Mounting 3. Gas connections 4.
3 Operation 3.1.2 Model OT-2 System Mounting the Analyzer The OT-2 System is designed for bulkhead mounting. Figure 3-1 is an illustration of the OT-2 System and mounting hole dimensions. There are four mounting holes—one in each of the inside corners of the rigid enclosure.
Model OT-2 System Operation 3 All operator controls are located inside the system enclosure, which is hinged on the left edge and provides easy access to the transmitter, sensor and cell block inside the instrument. The main enclosure door will swing open when the slotted latch at the right center of the door is turned counter-clockwise. Allow clearance for the door to open in a 90-degree arc at a radius of 16 inches. See Figure 3-1. 3.1.3 System Connections Figure 3-2 shows the Model OT-2 System.
3 Operation Model OT-2 System To connect gas lines to the Model OT-2 System: 1. Insert the tube into the tube fitting, and finger-tighten the nut until the tubing cannot be rotated freely, by hand, in the fitting. (This may require an additional 1/8 turn beyond finger-tight.) 2. Hold the fitting body steady with a wrench, and with another wrench rotate the nut another 1-1/4 turns.
Model OT-2 System Operation 3 Transmitter Cover Screws (4 places) Display Electrical Connections To Sensor Span Figure 3-3 Front View of Transmitter System Power Requirements: The Model OT-2 System requires a 12 VDC (nominal), reverse polarity protected power source. Observe good wiring practices. For hazardous area applications, the Model OT-2 System must be powered by a source that is consistent with intrinsically safe operation.
3 Operation 3.2 Model OT-2 System Installing the Micro-Fuel Cell The Micro-Fuel Cell is not installed in the cell block when the instrument is shipped. Install it before the analyzer is placed in service. When the micro-Fuel Cell needs to be installed or replaced, follow the procedures in chapter 5, Maintenance, for removing and installing cells. Recommendation: During installation, minimize the time the sensor is exposed to atmospheric oxygen, i.e.
Model OT-2 System Operation 3 The span gas cylinder must be equipped with a pressure regulator with a metallic diaphragm. The regulator should be set to approximately 3-5 psig. Rotate the selector valve (a) to the span position and observe the flow meter (b) which should indicate a flow of about 0.4 scfh. For calibration purposes the flow can be increased to as much as 1 scfh in order to reduce the time required to stabilize.
3 Operation Model OT-2 System NOTE: This procedure is more critical on the 0-10 ppm range and less critical on the 0-100 or 0-1000 ppm range. 3.3.2 Setting the Span Pot 1. Switch the system from zero gas to span gas and allow time for stabilization. Display Span Span Pot Figure 3-6: Span Pot Location NOTE: The span gas should have an O2 concentration of 80% 100% of full scale.
Model OT-2 System Operation 3 3.3.3 H2S Scrubber The life expectancy of the stainless steel H2S scrubber, included in this system, is determined by the amount of H2S passing through it. With the maximum concentration of 200 PPM H2S and a flow rate of 0.2 scfh the expected scrubber life will be over 6 months with Purifil® and over 11 months with Purifil® II. This scrubber life expectancy increases with lower H2S concentration or gas sample flow rates.
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Model OT-2 System Maintenance 4 Maintenance 4.1 Routine Maintenance Aside from normal cleaning and checking for leaks at the gas connections, routine maintenance includes servicing the filter, the scrubber, installing replacement Micro-Fuel cells and recalibration. For recalibration, see section 3.3 Calibration. 4.2 Cell Replacement The Micro-Fuel Cell is a sealed electrochemical transducer with no electrolyte to change or electrodes to clean.
4 Maintenance Model OT-2 System To replace the cell: Figure 4-1 1. Open the enclosure door. 2. Undo the velcro straps. 3. Remove the insulation. 4. The cell block is located in the center of the unit. Unscrew the cap on the bottom of the cell block. The B-2C sensor should drop down once the cap is removed.
Model OT-2 System Maintenance 4 4. Place the new cell on the cap with the sensing surface face down and the gold contact rings up. 5. Position the cell and cap so that the cell is inside the cell block. Press up on the cap and rotate. Tighten the cap screws. 4.2.1 Cell Warranty The cell warranty is sensor specific. Please contact Teledyne Electronic Technologies/ Analytical Instruments on explicit warranty on sensors.
4 4-4 Maintenance Model OT-2 System Teledyne Analytical Instruments
Model OT-2 System Appendix Appendix Specifications: System Enclosure: NEMA 4 Rated, bulkhead mounted Power Requirements: 9-16 VDC and 16-275mA. Ranges: 0–10ppm and 0–100ppm Oxygen or 0-100 ppm and 0-1000 ppm O2. Accuracy: ± 2% of full scale at constant temperature and pressure (temperature and pressure of calibration), except ± 1ppm on 0–10ppm range. ± 5% of full scale over operating temperature range (once thermal equilibrium has been reached), except ± 1ppm on 0–10ppm range.
Appendix Model OT-2 System Recommended Spare Parts List Qty.
Model OT-2 System Appendix Material Safety Data Sheet Section I – Product Identification Product Name: Manufacturer: Address: Phone: Micro-Fuel Cells Mini-Micro-Fuel Cells, all classes Super Cells, all classes except T–5F Electrochemical Oxygen Sensors, all classes.
Appendix Model OT-2 System Section III – Physical Hazards Potential for fire and explosion: The electrolyte in the Micro-Fuel Cells is not flammable. There are no fire or explosion hazards associated with Micro-Fuel Cells. Potential for reactivity: The sensors are stable under normal conditions of use. Avoid contact between the sensor electrolyte and strong acids.
Model OT-2 System Appendix Section V – Emergency and First Aid Procedures Eye Contact: Skin Contact: Ingestion: Inhalation: Flush eyes with water for at least 15 minutes and get immediate medical attention. Wash affected area with plenty of water and remove contaminated clothing. If burning persists, seek medical attention. Give plenty of cold water. Do not induce vomiting. Seek medical attention. Do not administer liquids to an unconscious person. Liquid inhalation is unlikely.
Appendix A-6 Model OT-2 System Teledyne Analytical Instruments
