Seal Condition Monitoring: From Sensors to Predictive Maintenance

Many factories still replace seals according to a fixed schedule or wait until leakage occurs. Condition monitoring allows for early detection of damage and intervention only when necessary, shifting from passive to data-based maintenance.

Three maintenance approaches

Reactive maintenance repairs after damage has occurred, which can cause sudden machine stops. Scheduled maintenance replaces according to a schedule, which may be too early or too late. Condition-based and predictive maintenance relies on actual data to decide when to intervene.

Commonly monitored parameters

• Pressure and temperature of the sealing or buffer fluid.
• Liquid level in the tank and rate of depletion.
• Air leakage flow and pressure difference in dry gas seals.
• Seal housing temperature and pump vibration.
• Motor current and acoustic or ultrasonic signals in advanced systems.

From data to alerts

Sensors send signals to the data collector, which transmits them to the control system or analysis software. When a parameter exceeds the threshold or changes abnormally, the system alerts for planned maintenance instead of emergency repairs.

Signs that can be detected early

• Gradually decreasing sealing fluid level: internal or external seal leakage.
• Increasing seal face temperature: loss of lubrication or poor cooling.
• Increasing air leakage flow: dry gas seal face wear or contamination.

Implementation steps

• Select critical equipment with a history of seal failures to start with.
• Choose suitable sensors for the installation location and environment.
• Collect baseline data when the equipment is operating normally to set thresholds.
• Integrate alerts into the control system and train operators.

Benefits and notes

Reduce unplanned machine stops, extend seal life by intervening at the right time, and have data for analysis when failures occur. Overly tight thresholds will cause false alarms, while overly loose thresholds will miss alerts. Contact SNS-VN for consultation on monitoring solutions.

References

Compiled from common technical practices for condition monitoring of rotating equipment.