How do you perform a holiday test?

Holiday test or a Continuity test is one of the non destructive test method applied on protective coatings to detect unacceptable discontinuities such as pinholes and voids.

The test involves checking of an electric circuit to see if current flows to complete the electrical circuit.

A Holiday test or Continuity test is performed by applying low voltage (connected in series with an LED or noise-producing component such as a piezoelectric speaker) across the chosen path.

If the electrical flow is detected then the test area is termed as conductive indicating presence of discontinuities such as pinholes and voids.

This test is commonly used in the offshore industries where piping and structures are coated with non-conductor coatings.

LMATS professionals are trained in Holiday (Continuity) test method in accordance with AS 3894.1, ASTM G62 and similar national and international standards.

Holiday Test by Wet Sponge Detector

Now, this test uses two 2 different voltage settings. The first is the 9V setting for thicknesses of 300µm or less and the second one is 90V for greater thicknesses up to 500µm.

Now let’s talk more about this instrument. The wet sponge detector consists of:

• An Open-cell sponge

• A set comprising of a connector and a shaft

• Audible discontinuity indicator

• A ground cable

• A wet sponge device

Phew! Finally done with our little “wet sponge”.

Holiday Test by High Voltage Detector

Now that our little “wet sponge” is out of the way, let’s move on to high voltage spark testing.

This test is reserved especially for thicknesses greater than 500µm.

Beware though, if you conduct this test on thicknesses that are any smaller, you run the risk of damaging your precious coating. We don’t want that, now do we?

The detector for this test is further divided into two distinct sub-types;

• Direct current

• Pulse type

You can’t test if you don’t know how to setup the detector, can you? The setup consists of:

• Electrodes,

• a ground cable,

• and an electrical device

In this case though, there is no specific voltage, so you have to look at the manufacturer’s specs for details. For example, when dealing with thicknesses of 1000µm ranging up to 1500µm, the specific voltage is around 5000V.

Applicable Standard

Now remember that regardless of whichever method you use, make sure that the coating is thoroughly dried out and fully cured as per manufacturer specifications.

Oh and also, don’t forget that the standard applicable here is ASTM D5162.

And, it is recommended that the Quality Control Coating Inspector must always refer to this specification religiously to get the right information so that they can perform the test effectively.

Now you know how to conduct a holiday test.

Happy testing!