MODEL 365A & E365A
INSTRUCTION MANUAL
VIBRASWITCH
®
MALFUNCTION DETECTOR
909GF294
PAGE 12
by the
Vibraswitch
®
so that Alarm and/or Shutdown of operating machine will not result from false,
transient disturbances. Examples of transient disturbances are the closing of pipeline check valves on
pumping applications, the start up of additional pumps on a line, and the initial start up of various
operating machines. These disturbances may cause the
Vibraswitch
®
to “trip” if the vibratory shock
level is in excess of its setpoint.
The purpose of the
Vibraswitch
®
Monitor is to “supervise” and “sort out” the transient disturbances so
that Alarm or Shutdown is not falsely imposed on the machine being monitored, but any continuous
vibration level, which exceeds the Setpoint of the
Vibraswitch
®
, will cause Alarm and/or Shutdown.
4.2
ADJUSTMENTS OF OPERATING SETPOINT
The operating setpoint for the
Vibraswitch
®
varies with the type of machine and its location
(measurement point) on the machine. The setpoint adjustments suggested in this manual are for
machines, which are functioning in a “good” or “normal” condition. This method follows the concept of
vibration tolerance for the machine and in this case is dependant upon an individual who is experienced in
the operation of the machine vibration as “normal”, “fair”, “slightly rough”, etc. These various degrees of
machine vibration are therefore, based on the individual’s physical perception between normal and
abnormal roughness while the machine is operating.
This method can lead to differences in the classification of the degree of vibration between individual
observers. Robertshaw believes that if the machine is operating satisfactorily, as previously defined, and
the acceleration sensed by the
Vibraswitch
®
is within certain limits, the settings made as outlined in the
following instructions will offer protection of the machine and prevent catastrophic failure.
For example, assume that a relatively new machine, which, to an experienced observer, is operating as
“smooth” or “good” regarding vibration and the Vibraswitch,
®
measures this acceleration level to be 0.25
g above its static condition (zero). Experience suggests that an acceptable setting for alarm conditions
would be a minimum of twice this value, or 0.5 g. It is acknowledged that such a definition of upper
vibration limit (alarm condition) on the machine may not adequately define the upper tolerance limit of
the machine before major repairs are required or excessive machine damage occurs. It does, however
define a limit that has proven to be “safe”. As the user becomes more experienced using the
Vibraswitch
®
as a monitoring device, his experience may indicate that a higher setpoint is acceptable on
the particular machine.
Note: Each scale division is ~0.1g and One full revolution is ~1.0 g.
Figure 4-2. Setpoint Adjustment
