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