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Belt weigh feeder Zero and Span Drift

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Fault Log · Field Report Schenck Weigh Feeder — Zero and Span Drift, Two Different Root Causes Plant: Cement  |  System: Schenck weigh feeder, belt scale, hopper load cells  |  Downtime: None Symptom A Schenck weigh feeder started showing both zero drift and span drift at the same time. Two separate accuracy problems showing up together made this a two-part investigation from the start — zero and span errors don't always share the same root cause, even when they appear together. Investigation — Zero Drift Started with the load cell loop and mechanical side of the belt scale: Load cell loop — checked the full loop, cleaned the load cell area. Idlers/rollers — checked the rollers for wear or misalignment. Belt tracking — with the belt empty, noticed it was drifting to one side. Zero was being tared in that empty, drifted position. Once material loaded onto the belt, the belt tracked back closer to center — meaning the zero reference had been tak...
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Zirconia Oxygen Analyzer Reading Maximum O2

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Fault Log · Field Report Zirconia Oxygen Analyzer Reading Maximum O2 — Not the Cell, a Rusted Outlet Plant: Cement  |  System: Zirconia oxygen analyzer, sample extraction system  |  Downtime: None Symptom The zirconia oxygen analyzer started reading maximum oxygen — pegged at the top of the range rather than tracking the actual process value. A reading stuck at maximum on a zirconia cell usually means the cell is seeing something close to ambient air instead of process gas, which points straight at a sample delivery problem before you even think about the analyzer itself. Investigation Started at the sample path, from the process side inward: Probe, extractor filter, sampling line, pump — checked the full sample path from the probe through the extraction filter and sampling line, including the sample pump. Performed a leakage test across this section. All found ok. Panel-side tubing and membrane filter — checked all tubing inside the panel along...
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Control Valve Positioner Calibration

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Practical Procedure · Calibration Control Valve Positioner Calibration — Full Stroke, Limits, and Auto vs. Manual Applies to: Pneumatic control valves with smart/digital positioners (e.g. HART-based) or conventional analog positioners  |  Equipment needed: HART communicator (for smart positioners), air supply/regulator, mA source or 4–20 mA loop calibrator Control Valve: Throttling the Flow ACTUATOR As the PLC output signal changes, the actuator rotates the internal disc — from fully open (parallel to flow) toward fully closed (perpendicular to flow). This is exactly why a control valve isn't just "on/off" like a block valve: it throttles anywhere between 0% and 100% to hold a process variable at setpoint. Before You Start Confirm the valve is safe to stroke — coordinate with operations, since a full 0–100% stroke will move the valve through its complete range on a live process line. Chec...
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