MICON 500C Electronic Sequencing
39
234AY00.INS R06
Computer Installation Guide
8.8
FAILURE PROTECTIONS (CONT’D)
2.
Mass Flow Meter Gas Temperature Transducer (optional):
Since this is a 4 to 20 mA device, the same hardware input margins apply as for pressure
transducers. The mass flow meter output will typically swing to 2 mA or 22 mA on failure.
3.
Ambient Temperature Probe:
This is not a 4 to 20 mA device. However, much in the manner of the Kraus ATC probe
failure detection, the system is able to detect a fault and cause a shutdown. Normally this
means if the temperature goes beyond the range of –50
°
C to +50
°
C, a shutdown will occur.
8.9
SYSTEM REDUNDANCIES
Some jurisdictions require redundancy of the key pressure sensing elements. For these applications, a
second pressure transducer input has been added. The key element of redundant pressure
transducers is the ability to verify proper transducer operation. PTX2 (pressure transducer two) is used
in conjunction with PTXI (pressure transducer one) to find an average value for PTX for comparison
against the target pressure.
In some jurisdictions backup from a second pressure transducer is not required. Through settings on
the INFO-PAC transmitter, the system is able to enable or disable use of the redundant pressure
transducer. When disabled, it is completely ignored. When enabled, the basic compensation formula
averages the readings from the two pressure transducers, and monitors the difference between the two
for a maximum window of error.
A deviation greater than 3 percent between PTX2 and PTX1 readings is considered a major fault,
triggering an immediate system shutdown, with manual reset only through the MRST (manual reset
switch) input.
8.10 ALARMS
Table 12 next page displays conditions which result in an alarm and shutdown of the system.
Ø
Shutdowns which can be reset only through the manual MRST (manual reset switch) input or push-
button will always register on the ALARM output.
Ø
Shutdowns which are automatically reset (e.g., with the handle switch) will only register on the
ALARM output if the INFO-PAC ALARM option is set to "all". The other INFO-PAC ALARM setting
is “man”, which enables a manual reset only.
During a system shutdown due to an alarm, the buzzer is set to operate on a 1 second ON/OFF cycle
interval. The buzzer stops sounding when the alarm is reset.
