Diesel & Gas: Part 3 - 2 Pages

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Diesel & Gas: Part 3

Catalog excerpts

DIESEL AND GAS ENGINES ENGINES Engine diagnostics Pole bands A pole band strapped to large shafts is a proven approach to generate signals using contactless sensors. It is also a cost effective alternative to using very large pole wheels. The pole band is delivered in a standard length of 3000 mm. At the beginning of the band the first 6 fastening hooks are looking to the opposite direction to the rest along the band. The band can be cut to the desired length. To maintain a certain tension, the pole band must be cut slightly shorter than the circumference of the shaft. Introduction The theory that the variable component of an engine’s crankshaft speed contains valuable information on the behavior of an engine has been known for many years. The linear motion caused by the compression and combustion cycles influences the speed of the crankshaft as the engine rotates. These speed variations are captured and analyzed by the engine diagnostic system MDS4000 The elements used for the monitoring of diesel and gas- engines or pumping compressors are: • Polebands of variable length that can be used to get the speed information, should there be no direct access to a toothed wheel of the rotating machine. The analysing software. Either as a ready to be installed box that can monitor the prime mover permanently or as a software package that can deliver the desired behaviour information on demand. Speed sensors For speed measuring including analyses of speed signals for regularity of movement it is recommended to use a speed sensor that has an output signal with a low jitter behavior. It is also important that it can cope with the interrupted magnetic signature where the two band ends join. Recommended speed sensors for this application are: • • Zero speed hall-effect sensor type High temperature VR sensor type Speed sensors that are able to deliver jitter free and sufficiently fast signals for the analysing software. Due to inertial forces the pole band will be limited in its maximum allowable rotational speed. Make sure to consult the relevant calculation on this subject. Many other dimensions in the same sensor families are available, either with integral connectors or (as shown in the drawing) with integral cables. The duty cycle of the sensor/pole band combination should be ideally very close to 50 : 50%. Typically at the band end there is a wider gap which can be used for synchronization purposes (see highlighted section of the speed trace).

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TECHNOLOGY GROUP Containing an industrial PC with a special input card to accept sensor signals directly from the speed sensors, the box presents itself as a robust, sealed and easy to be installed item. The box also contains a relay output card that can be assigned alarm functionality and deliver status information about the engine to Depending on the demand there is the possibility to drive a local display or to deliver failure information through a GSM module to a remote control centre. Locally the detailed information is stored for later access by authorized Failure indication based...

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