4.3.1 Function of the VISATRON
®
VN2020 / VN2020 EX oil mist detector
The VISATRON
®
VN2020 / VN2020 EX oil mist detector from Schaller Automation is
designed to protect large engines (gas, diesel and dual fuel) from oil mist explosions
caused by the spontaneous development of oil mist in the crankcase. It is part of a
safety system to protect the life and health of operating personnel and it permanently
prevents serious consequential damage.
The central part of the oil mist detector, as shown in Figures 12 and 13, is the
measuring head (3), which includes an optical measuring track under the inspection
cover (4) and an LED display (9) to display all important information for the user under
normal operating conditions. The measuring head is attached to the base plate (1) via a
vibration-protected mounting plate.
The oil mist detector uses the Venturi principle to take in the oil mist atmosphere from
the crankcase. The negative pressure generated by the Venturi air jet pump (6) at the
device is used to draw in the oil mist-containing crankcase atmosphere from the
crankcase via the engine wall connections (Fig. 10, 3). It then passes through the
header pipes (Fig. 10, 7) and the intake line (Fig. 10, 6) into the connection box and
from there into the optical measuring track in the measuring head, where the oil mist
concentration is continuously measured and analysed. From there, the crankcase
atmosphere returns to the crankcase via the recirculation line (Fig. 10, 9).
The active and continuous intake of the crankcase atmosphere ensures that there are
short response times between the formation of oil mist and the oil mist alarm to be
generated.
To avoid false alarms in the crankcase, such as from spray oil, the intake system uses
intake funnels specially developed by Schaller Automation that can always be used,
regardless of the direction of rotation of the engine. Where possible, Schaller
Automation recommends installing as shown in Fig. 27 of this manual. One intake funnel
is always required per intake point, which is directly connected to the engine wall
connection.
To avoid residues of oil (condensed crankcase atmosphere) in the intake lines, Schaller
Automation uses its own tried-and-tested drainage concept to return the excess oil to
the engine crankcase.
Additional draining components ensure that the system operates correctly under all
operating conditions.
The measures described for the device to function correctly mean that the VISATRON
®
VN2020 / VN2020 EX oil mist detector can be used primarily in maritime applications,
i.e. on ships with their static or dynamic angle of inclination, as well as in stationary
applications such as power stations.
The oil mist detector has been developed by Schaller Automation according to
IACS UR M10 guidelines.
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