Motcom BeCOMS BCom, User Manual, Page: 9 / 82

motcom® BeCOMS® | BCom
User Manual
Release
130301 (revision 190211)
Page 1.1
1.1. Components
1. System Description
1.1.1. BCom - Principle
The BCom system can be used on engines and motors (turbines, pumps, etc.)
where the crankshaft is not electrically isolated from bearing shells. It utilises the
thermo-electrical (Seebeck) effect for monitoring the condition of the engine/motor,
bearings and slip surfaces, allowing to recognise failures at an early point, which
prevents large-scale part damages.
On diesel engines, the BCom system measures and evaluates thermal voltage
between the crankshaft and bearing shells, signalling changes that can be
interpreted as dangerous.
Dry friction
R
V
Fig. 1.1. Measurement principle in a diesel engine
This thermovoltage is very low (< 1 mV) during normal engine operation while the
lubrication oil acts as electrical isolation. If the oil film between a rotating part and
its bearing becomes thinner and ruptures, which can be caused for example by
presence of metal particles in a bearing clearance, when the engine crankshaft
rubs against a bearing shell, the thermovoltage detected by SRE sensor rises.
Fig. 1.2. Redundant thermovoltage measurement