ABB KPM KB2 Sheet Break Detector

Description

System components

KPM KB2 fiber optic sheet break detection system contains:

 Sensor head installed above or under the web.

 Fiber optic cable protected with a flexible conduit.

 Display unit housing the light source, detector, and the measurement computer.

KPM KB2 is a solution to high temperature sheet break applications. The light source, detector,

and electronics are isolated from the high temperature environment by a 6 m (20'), 9 m (30') or

12 m (40') fiber optic cable. While the sensor head is exposed to high temperatures, the

electronics is mounted in a less hostile environment.

Sensor head "eye" holes are kept clean by purging instrument air through the sensor housing.

Flowing air keeps the eyelet holes clean and prevents dirt or steam from contaminating the

active optic surfaces. Purging air helps also to keep the sensor head temperature lower in high

temperature applications.

KPM KB2 requires clean instrument air at 0.5 – 3.0 bar (7 - 40 psi), the rotameter or pressure

regulator can be used for the easy detection of airflow.

Operating principle

The KPM KB2 operates on a proven, non-contact reflection principle. The light source can be

either RGB LED (red, green, blue) or IR LED (infrared). The optical sensor is placed above or under

the web. Applications include paper or board webs, wires or felts. Thanks to the unique RGB

detection method the color of the product or the felt has no effect on the measurement

reliability. The sensor is neither affected by dirt, steam nor temperatures up to 180 °C (356 °F)

when installed according to ABB Oy, KPM specifications. There are no electronic components

located in the sensor head.

The optical sensor is connected through a fiber optic cable to the RGB/IR light source located in

the display unit. The RGB/IR LEDs emit pulsed red, green, blue, or IR light onto the web surface.

The reflected light is received and transmitted through the fiber optic cable to the detector. All

light components are analyzed fast for a reliable break detection.

A break activates a relay, which can be connected to the logic control of a paper machine. The

reflected light intensities are also available as optional 4 - 20 mA analog outputs.

The self-cleaning sensor head is a 33.7 x 1500 mm (1" x 59") stainless steel tube with two holes

serving as eyelets for the fiber optics and outlets for purge air. Continuous airflow through the

stainless steel enclosure keeps positive pressure around the sensor head's eyes and keeps the

eyelets free of steam, dust or debris. The openings should be located towards the surface being

monitored.

KPM KB2 with +24 VDC + power supply

Relays are of dry contact types. In normal operation the "Break Out On" relay is open and it closes

during a break. In case the power is lost or turned off the "Break Out On" relay remains open

(disabled). "Break Out Off" works in the opposite way. There is 2 parallel Break Relays, Break Out

1 and Break out 2 which are working simultaneously.

”Alarm Out Off" is normally closed. It opens in case the built-in self-diagnostics detects a failure.

If power is lost or turned off the "Alarm Out Off" is OPEN. "Alarm Out On" works in the opposite

way. There is 2 parallel Alarm Relays, Alarm Out 1 and Alarm out 2 which are working

simultaneously.

Fiber optic cable is connected to the optics block. It does not matter which one of the two cables

is connected to the receiver inlet (Rx). In a normal application another cable is connected to the

RGB light source. IR light source is used in special cases such as heavy steam environment or in

an application where exceptionally strong light is needed.