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 the leak of volume or of the pneumatic drive in the application. This preventive maintenance app serves to detect damaged or aged tubing and leaks which come about suddenly. The Motion App also detects leaks from cylinder or valve wear from 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 extends and retracts multiple 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. For this reason, you need to enter the system parameters correctly.
With the default setting, the measurement of the pressure change will only be started when most of the pressure changes have faded away through the temperature dynamics. A longer lock-in time will be required depending on the volume. For the calculation of 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 respective connection of the valve is also provided. For determining the status threshold, homing must be carried out when the status of the system is good. Here, the leakage reference value will be determined, e.g. upon installing the system. The reference values are being saved persistently and stored to a parameter set. If there is a valid reference value for the leakage, the currently determined leakage volumetric flow rate 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 number value (0, 1, 2, 3) or as a traffic light (red, orange, yellow, green) as per VDMA standard.
The Motion App „Leakage diagnostics“ can be executed at the same time at all valve positions of the related Festo Motion Terminal.
- Flow:
- Measuring range 2 … 600 l/h
- Specifications in the Motion App and via PLC control:
- Start diagnostics
- Cancel diagnostics
- Start reference measurement
- Cancel reference measurement
- Return to controls:
- Status of the detection
- Leakage value at channel 2
- Leakage value at channel 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 to be pressurized will be considerably weaker. Correspondingly, the chamber to be exhausted will be significantly weaker. This makes sure that the permitted end position power is not exceeded.
- Notice:
- Homing should be done when the status is good, as this status/value will be applied for future leakage appraisals.
- An adjusted lock-in time will be required depending on the volume.
- When cylinders are used, which are not available in the database, this can lead to incorrect results.
- Restrictions:
- Not suitable for vacuum
- 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
- The weight force when the mounting position is not equal to 0 is always smaller than 75% of the pneumatic force
- So that the accuracies mentioned below can be maintained, you need to make sure that the drive reaches the corresponding end positions when extending and retracting
- The accuracy in details apply for: 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 membrane seat 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, the pressure being applied at the time will remain locked in, that is, the supply pressure in chamber 2 and the exhaust air pressure in chamber 4.
- When determining the leakage has been completed, all membrane seat valves of the main stage will be closed, that is, the pressure applied at the time will remain locked in.
