By lamps, buzzers or also in form of clear text DOLD fault annunciators inform on faults and conditions in electrical installations in industrial facilities and buildings. They also inform on work operations to be done. DOLD fault annunciators considerably reduce the time for fault finding in particular in complex machines and plants. Thus they help to minimize downtimes of production plants and save cost.
Apart from simple electrical group fault, new-value and first-up annunciators, electronic clear text fault annunciating systems are available for complex applications.
Especially when programmable logic controllers (PLC) or management systems are used it is indispensable to install fault alarm acquisition independent of the process level to keep control when the plant control fails and to avoid damages.
Monitoring of machinery and plants of any kind
... at a glance
Cost-effective, compact monitoring of small machines without PLC, e.g. compressors.
Modular design allows adjusting to plant extensions at any time (e.g. IL/SL 5990).
Central monitoring of multiple PLCs or centralization of multiple alarm relays for an overall overview on machinery and plants.
Allow selective indication of certain fault types on several monitoring centers. Group faults of the same type from many systems, channel and pass them well-aimed on to responsible expert personnel, e.g. insulation faults -> service electricians, low filling levels -> operating personnel, etc.
DOLDs text fault annunciators can be programmed in several languages, e.g. for foreign operating personnel. Statistics stored in the text annunciator help to optimize the plant operation. The products can be extended by a two-wire bus system. Open-circuit monitoring within the bus system when configured according to the de-energized on trip principle.
Prevent damages to man and machine in case of faults or even PLC failure.
Avoid costly production losses by early fault detection and thus allow the implementation of an improved operational reliability.
Reduce the time for troubleshooting by early and easy fault localization. Save time for fault finding.
Group fault, new-value and first-up annunciators have normally acoustic and visual indicators and are designed for DIN rail mounting or also for front panel mounting.
Group fault annunciators are available for 4 up to 160 signals and energize a relay when a fault signal occurs. Such a relay can be de-energized by an acknowledging key. A visual (flash lamp) or an acoustic (horn) transducer is connected to this relay output. New-value and first-up annunciators are used where the chronology of fault signals is essential.
The new-value annunciator signalizes that alarm among a number of alarms the status of which has changed last after the last acknowledgement. New-value annunciations are indicated by a flash lamp and after acknowldgement as permanent light until the fault is cleared.
The first-up annunciator signalizes that alarm among a number of alarms the status of which has changed first after the last acknowledgement. The first occurred fault is indicated by a flash lamp and consequential faults by permanent light.
Text fault annunciator systems
Text annunciator systems echo the correct sequence of the arrived fault signals. Stored alarms can be called up and viewed on the display. Text fault annunciator systems can be operated as new-value and also as first-up annunciators.
Text fault annunciators have outputs for group annunciation, horn and system readiness. Inputs and outputs are metallically isolated and thus ensure a maximum of interference immunity. Beyond standard applications, statistics, analog processing, time interrupt functions, decentralized acquisition and output as well as multilingualism of the fault texts are customer-specific options.
A printer can be used for logging, i.e. for printing date, time, test of the fault and the whole statistics memory of the system. With an appropriate programming software also other settings than message texts can be defined such as energized/de-energized-on-trip principle of inputs, delay of inputs as well as grouping and priority of outputs. A decentralized fault alarm acquisition in complex installations can be configured with up to 30 modules with 8, 16, 24 or 32 inputs each. Via a separate module, these modules are connected to a two-wire line which is connected to the central fault annunciator. A maximum of 957 fault alarms can be acquired with this. Additional remote control stations complete the system.
De-energized- versus energized-on-trip principle
De-energized on trip principle
For safety reasons DOLD recommends the de-energized-on-trip principle for fault annunciators. Here, the contact falls back in its normal position when the operating condition is met. Operating condition is loss of voltage which may be either due to a fault to be annunciated or to a fault in measured current transmission (e.g. damage of the supply cable). Thus, the wiring itself is included in the monitoring.
Energized on trip principle
The contact switches to its operated condition when the operating voltage is present, i.e. a fault alarm is initiated by an electric signal. Disadvantage: If the supply conductor to the fault annunciator is interrupted, neither this interruption nor any other fault can be indicated by the device. This is why DOLD recommends the de-energized-on-trip principle.
DOLD fault annunciators are used to specify maintenance intervals for preventive maintenance and for general monitoring in following application areas (among others):
Production plants, production sequences and processes
Machine functions, e.g. V-belt rupture, filter clogging, dry-running of pumps