ABB SCC Gas Preprocessing System Maintenance and Selection Guide

2.2 SCC-U common unit: the "distribution and control center" of the system

SCC-U is a 19 inch rack mounted (3U) comprehensive power and control chassis designed specifically for small extraction gas analysis systems.

Powerful power distribution capability: It can distribute single-phase power to various equipment such as analyzers, SCC coolers, SCC-K converters, heating sampling probes (such as PFE2/PFE3), heating pipelines (such as TBL01-S), etc.

Temperature control and calibration logic: Equipped with a built-in temperature controller, it can directly control the temperature of the heating filter and heat tracing pipeline. More importantly, it integrates up to 3 solenoid valves for test gas and ambient air, supporting automatic calibration switching at the cooler or probe end. The analyzer communicates with SCC-U through a 15 pin Sub-D interface (X32) to achieve calibration and fault interlocking.

Firewall for hazardous areas and corrosive gases

For situations containing acidic aerosols or in explosive environments, conventional filtration and drainage are no longer sufficient to ensure safety.

Acid Filter: When the SO3 content in the sample gas is greater than 1 mg/m ³ or SO2 is greater than 1000 mg/m ³ (such as flue gas from heavy oil or hard coal combustion), an acid filter must be installed. The borosilicate microfiber filter has a filtration efficiency of 99.99% for particles ≥ 0.1 μ m, effectively intercepting sulfuric acid aerosols and preventing corrosion of the analyzer chamber.

Explosion proof condensate monitoring (CGKW+ER-144A/Ex): The CGKW condensate monitor combines fine filtration and moisture detection functions. When a conductive liquid enters, the electrode will trigger a signal. If used in Zone 1 or Zone 2 hazardous areas, CGKW (must have a stainless steel casing) must be used in conjunction with ER-144A/Ex isolated switch amplifiers. The input of ER-144A/Ex is intrinsically safe (Ex ia), providing a maximum energy limit of 13.1V and 5mA to ensure absolute safety on site.

Flow and alarm monitoring (KFA isolation amplifier): For flow monitors measuring corrosive gases (such as chlorine gas), the accompanying switch signal needs to be connected to the control system through KFA isolation barriers (such as KFA6-SR2-Ex1. W). KFA can not only isolate the dangerous side, but also monitor line disconnection or short circuit. Once an external fault occurs, the red LED on the panel will flash and give an alarm.

Hard specifications for on-site installation and engineering wiring

Even the most advanced hardware can instantly fail if installed improperly. According to engineering practice, the following specifications must be strictly followed:

Rack installation spacing: When installing SCC-U, SCC-K, SCC-S and other equipment in a 19 inch cabinet, at least 1 height unit (1U) of heat dissipation space must be left between the devices. Especially the SCC-K converter, due to its operation at high temperatures of 320 ° C-680 ° C, must always be installed on the top floor of the cabinet to avoid heating up other analytical instruments.

Laying of heat tracing pipeline: The heating sampling pipeline must be laid at a downward slope. It is strictly prohibited to have U-bends or low-lying areas (water bags) in pipelines. Once condensed water accumulates in the pipeline, it will not only cause the dissolution of sample gas components (especially SO2 and NO2), but also cause gas resistance, resulting in a sudden drop in the suction of the diaphragm pump.

Life management of peristaltic pump tubing: Whether it is SCC-C or SCC-S, peristaltic pump tubing for condensate drainage is a vulnerable component. At a running speed of 5 rpm, its lifespan is usually about 5 months. A regular replacement plan should be established on site. Once the pump tube is found to be deformed, aged, or the discharge volume significantly decreases, it should be replaced immediately. Otherwise, if condensed water is sucked into the sample gas path, it will directly damage the analyzer.

Sealing and pressure testing: The airtightness requirements of the entire SCC system are extremely high (usually requiring 5 × 10 ⁻⁶ hPa/s). When connecting PVDF or PTFE pipelines, ensure that the clamp or sealing ring at the joint is securely fastened in place. When using a pressure reducing valve (such as ABB two-stage stainless steel pressure reducing valve), it is recommended to adjust the outlet pressure between 10-150 kPa to match the feeding requirements of the system.

Common troubleshooting and maintenance strategies

Engineers in the "search solution" phase often face emergency situations such as equipment alarms or data drift. The following is a high-frequency troubleshooting checklist for the SCC system:

Phenomenon: The analyzer reading is low or severely lagging.

Troubleshooting: Check if the temperature of the heat tracing pipeline meets the standard (usually set at 120 ° C-180 ° C). Check if the membrane filter is clogged with dust or aerosols (due to excessive pressure drop). Check if the diaphragm of the SCC-F/S feed pump has ruptured, resulting in insufficient pumping volume. For acid filters, observe if the filter element changes color or if the pressure drop exceeds 50 hPa.