This paper introduces the basis structure and major function of an on-
line condition monitoring system linked by a fibre-optic digital netwo
rk. Fibre-optic digital networks have obvious advantages to larger ent
erprises with various locations for condition monitoring data transmis
sion, which not only is an information highway between the main statio
n (diagnosis enter) and substation (monitoring locations), but also co
mbines the monitoring functions into one system. This is a two-level c
ondition monitoring system, The first level monitoring is realized by
a sub-station and the second level monitoring is realized by the main
station, The system has strong hardware functions and software functio
ns, which became a new model of real-time condition monitoring and was
used in many oil refineries. (C) 1997 Elsevier Science Ltd.