Acoustic Emission System for Insulator Crimping Inspection

Acoustic emission monitoring system at a glance

• Purpose: listens to the crimping process of a composite insulator and shows the moment the FRP core cracks, so the faulty unit is removed before it reaches the next station.
• Why it is needed: over-crimping produces cracks inside the core that are invisible from outside and that cause failures in test or in service.
• Measured quantities: pressure 0 – 30 MPa, sound intensity 0 – 110 dB, displacement resolution 0.01 mm.
• Output: live curves and a stored test record for every crimped unit, with automatic archiving of the data.
• Installation: sensors are added to the crimping dies; the frame and the original wiring of the crimping machine do not have to be changed.
• Users: composite insulator manufacturers running a crimping line.

1. What this system is used for

In the production of a composite insulator the metallic end fittings are pressed onto the FRP or ECR rod by a crimping machine. If the crimping pressure is too high, the fitting damages the rod and the core cracks inside the insulator, where nobody can see it. The unit passes the visual inspection and then fails a mechanical test, or worse, fails on the line.

This system watches the crimping operation itself. Acoustic sensors and pressure transducers are fitted to the crimping dies, and the signal is analysed while the fitting is being pressed. A cracking event produces a characteristic change in the recorded signal, and the software shows that change on the curve so the operator can identify the unit immediately and take it out of the batch.

It is a process monitoring tool, not a pass or fail judge: the software gives the operator a clear graphical reference on which to base the judgement. Over time it learns the signature of a good crimping operation, which reduces false calls.

2. What is inspected and how

• Cracks and breaks in the FRP core caused by excessive crimping pressure.
• Pressure of the crimping operation, monitored over the whole stroke.
• Displacement of the die, so the pressure and the geometry are seen together.
• Sound intensity from the acoustic sensors on the dies.
• Every unit, because the record is stored automatically with the product model, the voltage class and the crimping count, which also supports root cause analysis later.

3. Technical parameters

Scope of supply: control panel, computer, power distribution box, knobs, indicator, signal amplifier, communication board, acoustic sensors and probe, signal wires and the control software.

4. Key functions

• Live acoustic and pressure curve during crimping, so a cracking event is seen at the moment it happens.
• Automatic pattern recognition: the system learns the signature of a normal crimping operation and reduces false alarms over time.
• Flexible thresholds: pressure limits and sound intensity ranges are set per product specification.
• Test log storage: every crimp is archived with product model, voltage level, crimping count and the judged result, for compliance records and root cause analysis.
• Customisable report layout and curve output.
• Multi-language software interface for the shop floor.

5. Typical applications

• Composite insulator production lines – 100% monitoring of the crimping station.
• Quality control departments – objective record for every unit instead of a pressure value set by experience.
• Production engineering – finding the correct crimping pressure for a new fitting or a new core diameter and documenting it.
• Continuous improvement – trend analysis of archived crimping data.

6. Frequently asked questions

1. Does the system decide whether the core is cracked?

No. It gives the operator a clear graphical reference of the pressure and acoustic signature of each crimping operation, and the operator judges the unit. The software does not issue the final conclusion on fracture.

2. Do I have to modify my crimping machine?

No structural change is needed to the frame or to the original wiring. Sensors and signal receivers are added to some of the existing modules to monitor pressure and time during crimping.

3. Can it be installed on a crimping machine I already own?

Yes. The system is adapted to the crimping machine in use during integration, and Contune also supplies crimping machines with the acoustic emission system already fitted.

4. How is the system installed?

By default the buyer completes the installation by connecting the lines according to the video and the instruction manual. On-site installation at the factory is available as an option, with the travel costs borne by the buyer.

5. Is the interface available in my language?

English and Chinese are supplied as standard and further languages, such as French or Spanish, are added as a customisation package.

6. Why not simply control the crimping pressure?

Because the pressure value alone does not tell you when a particular rod has cracked. The acoustic signal shows the actual event on the actual unit, which is what makes it possible to remove that unit from the batch.

Related production equipment

This monitoring system belongs to the insulator production machines range and is normally fitted to a crimping station. It is available on the crimping machine CTCPM-140AS and comes as standard on the crimping machine 165. The insulator testing machines catalogue also covers the mechanical and electrical test machines used to inspect the finished insulator.