Intermittent Equipment Alarms and Shutdowns Traced to Terminals
Several months after we completed an electrical power and plant process controls project at a large manufacturing facility, Omni Instrumentation & Electrical Services was contacted by the plant manager requesting assistance with intermittent equipment anomalies and shutdowns that were occurring every few hours, with no discernible reason or pattern. The electrical contractor that had originally installed and wired the three large units had been unable to diagnose and fix the problems after several attempts.
Omni dispatched a senior instrumentation technician and a controls electrician to the facility where they met with the plant manager and two of the machine operators to go over the history of the problems. We reviewed the alarm logs for the equipment HMIs in detail, one by one, and found that many of the alarms were discrete points – E-stops, limit switches, and auxiliary contacts – but this was not the cause of the problems. We also checked all of the individual devices by performing a field loop check. Several small installation problems were found and repaired, but we determined that they were not the source of the intermittent shutdowns.
The source of the problems was finally discovered to be in the push-fit terminal blocks where bare wires had been used, resulting in poor connections. With the addition of ferrules to all of the wiring, followed by another loop check, the equipment returned to normal operation with no further nuisance alarms and shutdowns.
Omni Instrumentation & Electrical Services, Inc., located in New Jersey and Maryland, is a premier instrumentation and electrical contractor, providing superior total care solutions since 1986. Services include instrument installation, tubing installation, instrument calibration, control loop testing, startup and commissioning, power and lighting, process control wiring, BMS wiring, telecommunications and data wiring, fire alarm wiring, security wiring, process network wiring, and control panel fabrication. Omni Instrumentation & Electrical Services, Inc., is certified in Foundation Fieldbus, Profibus, DeviceNet and ASI-Bus installation.