Maintenance and troubleshooting of ABB SCC-K converter

2.2 Replacement of Catalyst Filter (NO2/NO Converter Only)

The lifespan of catalysts is usually greater than 6 months (under conditions of 30 l/h, 320 ° C, 10 ppm NO2, and 5% O2). When the conversion rate is significantly lower than 95%, it must be replaced.

Switching the bypass: extremely important! Before starting the replacement, the sample gas path must be switched to "bypass", otherwise the high-temperature corrosive sample gas will directly spray out and injure people.

Disassembly and assembly of components: Unlock the adapter through the rotating handle on the front panel and pull out the high-temperature tube furnace. Gently rotate and pull out the old filter element, remove the two outer O-rings and two inner O-rings. Do not damage the O-ring.

Install new filter element: Gently screw in the new filter element, making sure it is inserted into the bottom limit position, otherwise it may cause air leakage. Before installing into the tube furnace, the external O-ring can be slightly wetted to facilitate insertion (lubricating grease is strictly prohibited as it can poison the catalyst). Finally, tighten the handle.

2.3 Airtightness Test (Core Required Steps)

Whether replacing the quartz tube or catalyst, the converter must be cooled to room temperature for testing after assembly.

Switch the sample gas path to catalyst mode (green LED lights up).

Seal the sample gas outlet and connect the U-tube pressure gauge.

Use a shut-off valve to apply pressure, so that the pressure gauge reading is approximately 50 hPa.

Absolute red line: The maximum operating absolute pressure of NO2/NO converter shall not exceed 200 kPa; The thermal converter shall not exceed 120 kPa.

Observe for a few minutes. If the pressure drops significantly, it indicates a leak and the O-ring or joint needs to be rechecked.

On site high-frequency fault diagnosis and troubleshooting

When dealing with feedback from engineers searching for solutions, SCC-K's faults often focus on electrical heating circuits, air path blockages, and signal transmission.

3.1 The converter does not heat up at all

Phenomenon: The temperature controller displays abnormal or unable to raise temperature, and the conversion rate drops to zero.

Troubleshooting steps:

Measure heater voltage: Measure the voltage between terminals X4/2 and X4/3. If there is no voltage, it indicates that the heater is disconnected and needs to be replaced.

Measure controller output: Measure the voltage between terminals X4/6 and X4/7. If the voltage is less than 8V DC, it indicates that the temperature controller is damaged and needs to be checked or replaced according to the operation manual.

Testing Solid State Relays: If the controller output is greater than 8V DC but the heater has no voltage, it is usually due to the breakdown and damage of the Solid State Relay, which needs to be replaced directly.

Temperature control reset technique: If the set temperature is lowered by more than 10 ° C due to misoperation, the control logic of the sensor will release and cut off the heating circuit. At this point, it is necessary to wait for the actual temperature to drop below the new set value, then completely cut off the main power supply and reconnect it before resetting the temperature control system.

3.2 Non switching solenoid valve (optional dual solenoid valve version)

Phenomenon: Unable to switch between "bypass" and "catalytic" modes, or external control failure.

Troubleshooting steps:

Check the power supply and plug: Confirm if the 9-pin Sub-D plug (X2) is inserted correctly. SCC-K can only ensure normal operation when the plug is fully inserted.

Internal/External Control Conflict:

If internal switching (front panel switch) is used, there must be a short bridge between pins 1 and 6 of the Sub-D plug, otherwise the solenoid valve will not operate.

If external switching (customer DCS control) is used, the short-circuit bridge between No. 1 and No. 6 must be removed. At this point, the front panel switch will fail. The switching status is confirmed by the two green LED indicators on the panel.

3.3 Low NOx reading or no conversion rate

Phenomenon: The analyzer shows a much lower than expected NOx concentration or no response at all.

Troubleshooting steps:

Air path blockage/leakage: Check if the sample gas pipeline is blocked by dust or aerosols. Observe whether the flow meter has a flow rate. If the flow rate is zero, first check whether the front-end SCC-C or SCC-F feeding unit is normal, and then check the internal pipelines.

Catalyst failure: Confirm that the temperature is normal, but the conversion rate is below 95%. At this point, the catalyst filter element must be replaced.

Cross sensitive interference: Analyze the composition of the sample gas. If the concentration of ammonia (NH3) is too high, it will consume some NO2; If the sample gas contains high concentrations of SO2, and if an acid filter is not used to intercept SO3 aerosols at the front end, it can also cause the filter element to quickly become poisoned and fail.

Oxidation problem of NO2/NO: Due to the easy re oxidation of NO to NO2 in long pipelines, SCC-K converters should be installed as closely as possible to the analyzer, shorten the sample gas pipeline, and the temperature of the heat tracing pipeline must be stable above the dew point (recommended 120-180 ° C).