What Is a Pinhole Detector?
A pinhole detector is a device specifically designed to detect pinholes, which are small defects in equipment. A pinhole is a small hole that is created during the manufacturing process of a product. It is mainly caused by impacts and vibrations during movement, but can also occur during metal plating and welding processes when the gases and air generated cool and leave only air bubbles behind. A pinhole detector can find these tiny holes in a variety of ways.
Uses of Pinhole Detectors
Pinhole detectors are utilized to identify pinholes, helping to prevent product defects and equipment malfunctions, but pinholes occur in a variety of situations. These pinholes occur when impact is applied or friction is caused by vibration. Pinholes can cause leakage or corrosion of contents and must be found immediately. They can also be caused by plating and painting. The gases produced during painting can create pinholes. Pinholes can accumulate dirt and cause corrosion, so pinhole detectors are used to find them.
Principles of Pinhole Detectors
Various methods are employed by pinhole detectors.
- Bubble inspection
In the bubble inspection method, a foaming liquid is applied to the surface to be inspected for pinholes. If there are minute holes, bubbles are generated from the backside and pinholes can be detected. However, this method is not suitable for small pinholes because it is time consuming. - Ultrasonic Inspection
This method finds pinholes by detecting ultrasonic waves generated by minute holes. When compressed air is put into a container with a pinhole, air leaks out of the hole. This is spread around as ultrasonic waves, which are then examined with a detector. The position and size of the pinhole can be determined from the position and size of the ultrasonic waves generated. - Electric discharge inspection
This method uses the electrical discharge phenomenon to detect pinholes. Electrodes are attached to the front and back of the surface to be examined, and high voltage is applied. When a voltage is applied to the hole, the air insulation is destroyed, an electric discharge occurs, and current flows. The presence or absence of a pinhole is detected from the change in electric current caused by this discharge. In the case of painted surfaces and thin films, the high voltage may cause damage, so care must be taken.