As per our standard quality assurance and tank lining best practice the cured coating is then tested for pin holing using a DC Holiday spark tester. Any defects identified were marked prior to making good using the same material applied by brush. This is essential as a single pin hole in an aggressive hydrogen sulphide rich environment such as an anaerobic digester is a point at which degradation of the concrete can commence.
How does a holiday / spark tester work?
A holiday tester, also known as a spark tester or a pinhole tester, is a device used to detect and locate defects or discontinuities in the protective coatings of various materials, such as pipelines, tanks, and concrete structures. These defects, often referred to as “holidays,” can compromise the integrity of the coating and lead to corrosion or other issues. The holiday tester works by applying a high voltage to the coated surface and detecting electrical discontinuities that may indicate breaches in the coating.
Here’s a basic explanation of how a holiday tester works:
- High Voltage Source:
The holiday tester is equipped with a high voltage source, typically provided by a battery-operated circuit within the device.
- Voltage Adjustment:
The user can adjust the voltage level based on the specific requirements of the coating being tested. Different coatings may have different dielectric breakdown strengths.
- Probe or Brush:
The device is equipped with a probe or brush that is brought into contact with the coated surface. This probe is connected to the high voltage source.
- Voltage Application:
When the probe is in contact with the coated surface, the holiday tester applies a high voltage to the coating. This voltage is higher than the dielectric strength of the coating material but not high enough to damage it under normal circumstances.
- Detection of Holidays:
If there is a holiday or breach in the coating, the high voltage can penetrate the defect and create a spark or a current flow between the probe and the underlying substrate.
- Audible or Visual Alarm:
The holiday tester is often equipped with an audible or visual alarm system that signals the presence of a holiday. This alert indicates that the coating has a breach at the location where the tester is applied.
- Identification and Repair:
The user can identify the location of the holiday based on the audible or visual signals. Once identified, the damaged area can be marked for repair or further inspection.
It’s important to note that holiday testing is commonly used for non-destructive testing of protective coatings, such as paints and epoxies, to ensure their effectiveness in preventing corrosion. The method is widely employed in industries like pipeline construction, tank lining, and concrete structure protection.
The voltage level applied by the holiday tester is carefully controlled to avoid causing damage to the coating. The effectiveness of the holiday testing process depends on the skill and experience of the operator, as well as the proper calibration and functioning of the testing equipment.