Maintenance and commissioning of ABB KPM KB2 paper breakage detector

Practical Guide for Maintenance and Debugging of ABB KPM KB2 Paper Break Detector

On modern paper and cardboard production lines, the high-speed operation of the paper web is accompanied by a high risk of paper breakage. Once paper breakage occurs and is not detected in a timely manner, it not only leads to a large amount of waste, but also may cause catastrophic equipment accidents such as paper wrapping around the dryer and damaging the blanket. Traditional contact type paper breakage detectors are highly susceptible to interference from high temperatures, high humidity, dust, and paper fibers, and may even get caught up in the equipment during paper breakage. The ABB KPM KB2 fiber optic paper breakage detection system, with its unique non-contact reflection principle and sensor design without electronic components, is designed specifically for high-temperature and harsh papermaking environments.

For on-site engineers in the "search solution" stage, a systematic troubleshooting logic is often required when facing paper breakage, missed reports, frequent false alarms, or sensor failures. This article will provide a detailed engineering practical guide from four dimensions: hardware architecture, installation and wiring specifications, parameter calibration, and high-frequency fault diagnosis of KPM KB2.

Core architecture and working principle

The core design concept of KPM KB2 system is "optoelectronic separation", which means completely isolating delicate electronic components from extremely harsh on-site environments.

The entire system consists of three parts:

Sensor Head: A circular tube (diameter 33.7mm) made of AISI 316 stainless steel with a length of 1.5 meters, installed above or below the paper web. It has no electronic components inside, only two fiber optic collimation holes (Eyelets) for light emission and reception.

Fiber Optic Cable: Available in three length options: 6 meters, 9 meters, or 12 meters. It is wrapped in an airtight stainless steel flexible conduit to transmit the optical signal of the sensor head back to the control cabinet.

Display Unit: includes a light source (RGB or IR LED), a high-precision detector, and a measurement and calculation motherboard. It is usually installed in control rooms or walls away from high-temperature areas.

Working principle: The light source emits pulsed red, green, blue (RGB) or infrared (IR) light, which is transmitted through optical fibers to the sensor head to illuminate the paper web. The reflected light returns to the detector through another optical fiber. The great advantage of using RGB detection method is that no matter how the color of the paper or the color of the blanket changes, it will not affect the reliability of the measurement results. When the paper web breaks, the reflected light intensity will undergo a drastic change, and the system will trigger the relay output accordingly, interlocking the shutdown.

On site installation and gas path configuration specifications

Even the most advanced sensors, if installed improperly, can lead to weak or rapid signal failure. The following are the engineering red lines that must be strictly followed:

2.1 Sensor positioning

Measurement distance: The optimal distance between the sensor head and the paper web is 10-30 cm (4-12 inches).

Edge distance: The distance between the measuring point and the edge of the paper should be maintained at around 30 cm.

Avoid parallel installation: It is strictly prohibited to install multiple fiber optic sensor heads side by side and closely adjacent to each other. The light sources of adjacent sensors will interfere with each other, and at the same time, nearby infrared dryers will also cause serious optical interference.

2.2 Laying of Fiber Optic Cables

Fiber optic cables are very fragile and must be installed with extreme caution.

The best time to thread wires inside a catheter is when it is cooled at room temperature and the catheter is straightened on flat ground.

Tension limit: If pulling is required, force must be applied from the outer sheath of the optical fiber, and direct pulling of the connector is strictly prohibited. The maximum pulling force of two optical fibers shall not exceed 50 Newtons (11 lbf).

Bending radius: The minimum bending radius of optical fibers shall not be less than 50 mm (2 inches). Excessive bending can cause internal glass fiber breakage, signal attenuation, or even complete loss.

2.3 Purge Air System

The two optical holes of the sensor head are easily obstructed by paper wool, dust, or water vapor.

Air source requirements: Dry and clean instrument air must be connected, with a pressure range of 0.5-3.0 bar (7-40 psi).

Dual function: Continuous airflow not only creates positive pressure around the optical aperture, preventing dirt from approaching; It can also effectively reduce the temperature of the sensor head in high-temperature applications and prevent the aging of the sealing ring.

During installation, it is necessary to ensure that the Multi air seal is correctly inserted into the conduit liner and the tightening nut is tightened.

Practical debugging and Auto limit automatic limit calibration

The debugging of KPM KB2 is not simply about setting a fixed threshold, but requires the system to "learn" the actual lighting conditions on site. Divided into preliminary debugging and final debugging.

3.1 Preliminary debugging and signal optimization

Set the system to "Maintenance" mode, at which point the paper break relay is disabled to prevent false shutdown signals during debugging.

Use a dry paper to simulate the "paper on" state and place it in the normal position in front of the sensor.

Go to the Maintenance ->On line signals menu and observe the signal strength. Normally, it should be between 50-500. Adjust the angle of the sensor head to maximize the reflected signal (usually perpendicular to the paper surface).

Environmental light monitoring: Check the Environmental light parameter, which must be below 60%. If the ambient light is too high, the RX Gain can be reduced through the Measurement config menu, or external strong light sources can be physically obstructed.

3.2 Collecting reference values

In maintenance mode:

Simulate paper breakage: When there is no paper on the machine, press the SAMPLE key to store the current signal as "Break level".

Simulate paper: When the paper is running normally, press the SAMPLE key to store the signal as "Paper level".

3.3 Perform Auto limit calculation

This is the most crucial step. The system will calculate the Paper to Break Ratio based on the two sets of data you collected, and list the ranking of RGB and their combined signals in the paper to break state.

Go to Configuration ->Auto limit&Auto arm ->Calculate Auto limit.

The system will prompt which signal (such as G or B channel) has the largest difference ratio. The signal that usually ranks first is the best paper breakage detection signal.

Press the right arrow and ENTER, the system will automatically set the detection limit to the midpoint of 50% of the signal Paper and Break levels, and automatically determine the detection direction (such as Break<Limit).

Turn on the alarm (Auto arm), set the high and low limits and drift alarm direction.

Finally, switch the mode to 'Detect enabled' to enable paper breakage detection.

Attention: The final debugging must be carried out under real paper machine operation and real temperature environment, as thermal expansion and contraction will slightly change the mechanical distance.

Typical troubleshooting and countermeasures

During on-site operation, the faults of KPM KB2 are usually manifested as "false alarms" or "no alarms", and its built-in online signal monitoring and event logs are powerful tools for troubleshooting.

4.1 Alarm: Environmental light is too high

Phenomenon: The system detects external light interference, causing signal distortion and even triggering maintenance alarms.

Troubleshooting:

Is the sensor head too close to the paper (too reflective)? Adjust to 10-30 cm.

Is there a strong light source nearby directly shining on the sensor head? Move the light source or install a light shield.

Is the surface of the paper too shiny (with strong reflection)? Slightly tilt the sensor angle.

Solution action: lower RX Gain in Measurement config (for example, from 1.0 to 0.5) to reduce reception sensitivity.

4.2 Alarm: Drift Alarm

Phenomenon: The signal level gradually decreases, triggering a drift alarm.

Reason: The fiber optic lens or sensor hole is slowly contaminated by dust or paper wool, or water enters the sensor head, causing scaling on the fiber optic end face.

Troubleshooting: Check if the purge air has insufficient pressure or if the air source contains oil or water. If the signal shows a slow downward trend in online signals, it is necessary to arrange for fiber cleaning.

4.3 Alarm: Signal out of range, clean measures. probe (signal out of range, probe needs to be cleaned)

Phenomenon: The signal level is extremely low (below 3) or extremely high (above 1000).

Troubleshooting: There may be shredded paper directly sticking to the sensor head, blocking the view. Or the sensor hole may be completely blocked. The probe needs to be cleaned.

4.4 Communication failure: Optic data timeout

Phenomenon: Communication between the display unit and the connection board is interrupted.

Troubleshooting:

The flat cable on the measuring board is loose. Re plug and tighten.

Motherboard malfunction. If the error persists after restarting, the measuring board needs to be replaced.

Deep Maintenance: Fiber Optic Probe Cleaning Guide

When the air blowing system cannot remove stubborn dirt, it needs to be disassembled and cleaned. Improper operation can easily damage quartz optical fibers.

Disconnect the fiber optic connection of the display unit, unscrew the conduit sleeve, and allow the fiber optic cable to slide inside the conduit.

Remove the fastening screws at both ends of the sensor head, and remove the end plate and locking ring.

Carefully extract the fiber optic cable and gently wipe the lens end face with a cotton swab dipped in anhydrous alcohol. It is strictly prohibited to use hard objects to scrape.

When reinstalling, make sure that the two "eyes" of the fiber are centered and aligned with the holes on the stainless steel tube. If it is eccentric, the light path will be blocked, resulting in extremely weak signals.

It is strictly prohibited to pull the fiber optic cable forcefully throughout the process.