Leakage diagnostics
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Fewer system downtimes and faster fault detection due to preventive maintenance. Separate diagnostic cycles and specific threshold values enable you to detect and localize individual leaks in the application operated by the Festo Motion Terminal.
With the Motion App „Leakage diagnostics“ you can detect a volume leakage or a leakage in the pneumatic drive in the application. This preventive maintenance app is used to detect damaged or aged tubing and leaks which occur suddenly. The Motion App also detects leaks due to cylinder or valve wear early on. Process monitoring is not permanent.
The Motion App starts its own diagnostic cycle by approaching the two end positions. During the diagnostics, the cylinder advances and retracts several times. The leakage volumetric flow rate is mostly calculated based on the cylinder volume or the overall volume including the tube volume as well as the measured pressure change. You therefore need to enter the system parameters correctly.
With the default setting, the measurement of the pressure change will only start when most of the pressure changes have dropped off through the temperature dynamics. A longer lock-in time will be required depending on the volume. To calculate the leaks, the pressure drop will be determined at a valve (drive in end position).
In addition to the calculated leakage volumetric flow rate, the leakage status for the valve connection is also provided. To determine the status threshold, homing must be carried out when the system is in a neutral state. Here, the leakage reference value will be determined, e.g. when the system is installed. The reference values are continuously saved and stored as part of a parameter set. If there is a valid reference value for the leakage, the leakage volumetric flow rate currently determined is compared with the reference value and output as a leakage change (delta to the reference value) in l/h. Using the previously defined limit values for the delta, the status will be output additionally as a numerical value (0, 1, 2, 3) or as a traffic light (red, orange, yellow, green) as per the VDMA standard.
The Motion App „Leakage diagnostics“ can be used at the same time on all valve positions of the Festo Motion Terminal.
- Flow rate:
- Measuring range 2 … 600 l/h
- Specifications in the Motion App and via the PLC:
- Start diagnostics
- Cancel diagnostics
- Start reference measurement
- Cancel reference measurement
- Feedback to the controller:
- Status of the detection
- Leakage value at duct 2
- Leakage value at duct 4
- VDMA evaluation
- Pre-pressurization function:
- If, when starting the Motion App, the pressure in the cylinder chamber to be exhausted is more than
20% below the supply pressure, then the pressurization of the cylinder chamber will be considerably weaker. Correspondingly, the chamber to be exhausted will be significantly weaker. This ensures that the permitted energy in the end position is not exceeded.
- Notes:
- Homing should be carried out when the system state is neutral, as this state/value will be applied for future leakage assessments.
- An adjusted lock-in time will be required depending on the volume.
- Using cylinders that are not available in the database can lead to incorrect results.
- Restrictions:
- Not suitable for vacuum
- The temperature of the compressed air must be in the following tolerance range:10 °C … 30 °C (50-86 F)
- Possible supply pressure of the Festo Motion Terminal 0.5 ... 8 bar
- When the mounting position is not equal to 0, the weight force is always smaller than 75% of the pneumatic force
- You need to make sure that the drive reaches the corresponding end positions when advancing and retracting so that the accuracies mentioned below can be maintained.
- The accuracy applies to: 0 ... 50 l/h:
- Absolute accuracy:
- Small volume 0.072 l: ±7 l/h
- Large volume 5.074 l: ±15 l/h
- Small cylinder ADN-25-50-A-P-A: ±7 l/h
- Large cylinder DSBC-63-500-PPVA-N3: ± 10 l/h
- Repetition accuracy: ±10 l/h
- Status of the system when completing and canceling diagnostics:
- Volume: First, the volumes will be depressurized so that the pressure level of the exhaust air is set. Then, all diaphragm poppet valves of the main stage will be closed.
- Cylinder: Once the source of the leakage in the cylinder has been determined, all boosters will be closed. This means that the pressure applied at the time will remain locked in, i.e. the supply pressure in chamber 2 and the exhaust air pressure in chamber 4.
- When leakage determination has been completed, all diaphragm poppet valves of the main stage will be closed, i.e. the pressure applied at the time will remain locked in.
