Honeywell SMV800 User Manual page 65

Failsafe Switch
Absolute Pressure Failsafe
(PV2)
Revision 1.0
ON
OFF
ON
OFF
SMV800 Modbus User's Guide
Case1: If flow output is required to go
to failsafe when there is a pressure
failure, selecting Absolute Pressure
(PV2) failsafe will assure this.
If failsafe for the flow output is not
needed when a pressure sensor fails,
the nominal or design values for
pressure is used in the flow calculation
and the flow rate continues to be
reported. Some cases are listed below.
PV2 Process Input: If the PV2 input
becomes good, device needs a power
cycle to return to normal.
PV2 Sim Input: If the PV2 input
becomes good, device returns to
normal without a power cycle.
Case 2: This Switch ON: When PV4 is
mapped to output, bad PV2 (Process
input or Sim value) makes PV4 bad,
device goes to burnout.
PV4 calculated: If the PV2 input
becomes good (Process input or Sim
value), device needs a power cycle to
return to normal.
PV4 Simulated: PV2 input good or bad
(Process input or Sim value), PV4 is
not dependent on PV2. If PV4 sim
input is Bad, device goes to Burnout. If
PV4 Sim input becomes good, device
returns to normal without power cycle.
Case3: This switch OFF: If PV4 is
mapped to output, PV4 is still good on
bad PV2. PV4 calculation uses Design
Pressure or Nominal / Default
Pressure as below:
SMV3000, Standard:
Fluid = Gas: Flow equation Uses
Design Pressure.
Fluid = Liquid: Flow equation Uses
Default / Nominal Pressure.
Fluid = Steam: Flow equation Uses
Design Density. Design Pressure = 1
SMV3000 or SMV800 Dynamic:
Fluid = Gas, Liquid Steam: Flow
equation uses Nominal/Default
Pressure
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