Emerson Mobrey Hydratect 2462, Reference Manual

Page: 9 / 66

3
Reference Manual
24625020, Rev AA
Introduction
March 2017
Introduction
1.3.1 Steam and water detection
On each of the two electrically-isolated channels, the Hydratect 2462 system detects steam
and water by using the differences in their resistance and conductivity (
Figure 1-5 on
page 7 ).
Detection of steam and water is indicated by the illumination of a red or green LED on the
front panel of the Hydratect 2462 Electronics Control Unit (
Figure 1-1 on page 2 ).
The Hydratect 2462 system also provides status outputs from relays (one per channel) to
indicate the detected states. Each status relay has normally-open and normally-closed
electrical contacts to control external equipment.
Each Hydratect channel is individually set to a water-normal or steam-normal state by using
configuration ‘jumpers’
(1)
on a printed circuit board (PCB). The ‘jumpers’ must be set to
correspond with the normal state of the system. This allows the status relays to default to
the not-normal state if the Hydratect 2462 system developed a fault. For example, a status
relay is de-energized when a steam-normal channel monitoring a steam line detects water
(i.e. a not-normal state). In that situation, the normally-open relay contacts close and the
normally-closed contacts open. A latch option is available for each status relay, which, once
activated, holds the relay in the not-normal state until reset.
See “Setting the printed circuit board (PCB) jumpers” on page 23 for further information.
1.3.2 Contamination detection
To prevent a build-up of contamination causing a false indication, a contamination
detection circuit operates in parallel with the steam/water detection.
An error threshold for the contamination detection circuit can be set for high sensitivity or
low sensitivity by using ‘jumpers’ on a PCB. The circuit can be switched off if not required.
See
“Setting the printed circuit board (PCB) jumpers” on page 23 for further information.
Detected contamination on a Hydratect channel is indicated by the front panel fault LED,
and a fault relay (one per channel) is de-energized for use by external equipment.
1.3.3 Fail-safe operation
For reliability, each Hydratect channel has a separate power supply.
The Hydratect 2462 system continuously monitors itself for component failure, cable faults,
ground (earth) faults, and electrode problems. Components outside the self-monitoring
loop are in triplicate such that if two were to fail, the system would still function normally.
Component failures are indicated by the front panel fault LED and cause the fault and/or
status relays to be de-energized.
Hydratect 2462 system self-checking includes the signal and ground (earth) cable
terminations at the electrodes. The fault LED is illuminated and the fault relay is
de-energized if one or more conductors become detached.
The ways in which the LEDs and relays indicate the system state are summarized in
Table 1-2 and Table 1-3 on page 9 .
1. A PCB ‘jumper’ is a metal bridge that closes an electrical circuit. Typically, a ‘jumper’ consists of a plastic plug that fits over a pair of
protruding pins. By placing a jumper plug over a different set of pins, you can change a board's parameters.