Emerson NGA2000 TO2 Flow Sensor Replacement, Printed Circuit Boards, Troubleshooting

Model NGA2000 TO2

Instruction Manual

748374-F March 2003

Install replacement Sensor in reverse order. Check Sensor for leaks and add electrolyte as described in Section 2-2a on page 2-1. Rein- stall Sensor Assembly in Analyzer Module and reconnect J5 and J6 to the power board.

After installation of new Sensor, it will be neces- sary to load the new calibration data supplied with the Sensor. Enter the new calibration data by entering the Load Factory Calibration Data menu. You can get to this menu as follows: Main Menu, Technical Level Configuration, Ana- lyzer Module Diagnostics, Calibration Parame- ters, Load Factory Calibration Data. This menu screen will look as follows:

Load factory calibration data

Concentration 1:

Output 1:

Temperature 1:

Concentration 2:

Output 2:

Temperature 2:

Concentration 3:

Output 3:

Temperature 3:

HOME ESCAPE MORE

Figure 4-2. Load Factory Calibration Data Menu

The data is supplied with the new sensor and must be entered exactly as shown on the sen- sor data sheet. To enter the data for data points 4 & 5 and the sensor model, press the MORE soft key to access the next screen.

4-5 FLOW SENSOR REPLACEMENT

See Figure 1-2 on page 1-3 for Flow Sensor lo- cation. To replace Flow Sensor, remove all connecting hardware and undo connections to the sample line. The Flow Sensor is mounted to the Sensor Assembly mounting plate by two screws. Be sure to install the new Flow Sensor with the flow indication toward the outlet.

4-6 PRINTED CIRCUIT BOARDS

All three printed circuit boards can be replaced, if necessary. Refer to Figure 1-2 on page 1-3 for location of the Power, Network and Computer Boards.

To remove any PCB, disconnect the associated cables first. Tag each connector and its location before disconnecting any wiring. This helps in reassembly. The Power board and Computer board are located on a common bracket.

4-7 TROUBLESHOOTING

The following provides a short list of common troubleshooting tips. Additional information is contained in the Platform Manual.

The TO2 analyzer fails to purge down to ppm levels.

Prior to conducting any changes to the system, try running a quick start sequence (see Section 3-4 on page 3-3) to see if the oxygen reading goes lower. If the reading does decrease, the sensor has not been allowed sufficient time to consume the dissolved oxygen in the electro- lyte. If the reading continues to read high a leak may exist in the sample lines. The number one problem associated with trace oxygen analyzer installation is the occurrence of leaks in your sample plumbing. If the oxygen reading will not come down to ppm levels or is reading higher than expected, the sample plumbing prior to the instrument may have a leak. A quick check can be conducted by observing the oxygen reading at two different flow levels; 0.5 and 2.0 scfh. If the oxygen reading drops significantly when the flow is increased from 0.5 to 2.0 scfh, this is a good indication that a leak exists.

To check for leaks prior to the sensor, discon- nect the Analyzer Module and cap the inlet line. Pressurize the inlet line to 5 - 10 psig and check all connections with a soapy solution (SNOOP®) to identify leaks.

WARNING

SENSOR DAMAGE

Do not pressure check the sample line with the sensor connected. Over-pressurization of the sensor can result in damage.

The TO2 analyzer exhibits flow sensitivity.

Check to make sure that your vent line is not blocked. If you see a rise in reading with an in- crease in flow, you may be over-pressurizing the sensor due to a blocked vent. Since the

Rosemount Analytical Inc. A Division of Emerson Process Management Maintenance and Troubleshooting 4-3