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6.8 Trip Multiply
Trip Multiply was designed for large machines that pass through critical speeds (resonance) on start-
up. It allows “protection” to remain in place but the alarms are temporarily raised to a higher value (i.e.
9 mils instead of 3 mils). In practice, the startup of large critical machines is so closely monitored by
plant personnel that Trip Multiply is rarely used.
6.9 Avoid False Trips
Helping you avoid false trips is a high priority with B&K Vibro. Education is a large part of helping our
customers avoid false trips. Many of the following suggestions are common for any protection system.
6.9.1 Install an External Bypass Device
An external bypass device operates independent of the VC-8000 rack. An example would be a DPDT
switch that prevents trips by 1) keeping the trip circuit open (or closed) while you are working on the
rack and 2) notifies plant operations that the external bypass is active (see Error! Reference source
not found.)
If the VC-8000 trip relays are tied to a DCS you may not require an external bypass device; You can
simply add logic in the DCS to ignore the trip signal from the VC-8000 while you are working on the
rack.
Figure 6-1) External Bypass Circuit
6.9.2 If the Machine is Running – Don’t Touch the Rack.
Everyone has a story; “I just opened the cabinet, and the machine tripped”, or “All I did was touch a
wire etc.” Before you work on the rack, use an external bypass device.
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