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Diesel & Gas: Part 30 pages
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
DSS 1210.01 STV
DSE 1210.00 SHV
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.
D&G SpeedPackage 3.1
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).
www.jaquet.com
Tel.: +41 61 306 88 22
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