Knowledge Base

Porosity Holiday Testing, testing Do's and Don'ts - Video


Porosity holiday testing, the do's and don'ts of wet sponge and high voltage porosity testing.



Visit our Porosity product page for more information about our porosity detectors and accessories


Here's the video transcript for those who prefer to read

PCWI Porosity / Holiday Detectors. The instruments and support you need for your industry. Testing information, the Do's and the Don'ts.


PCWI manufactures a range of holiday detectors and a vast range of brush ware. We'll start this session with high voltage porosity testing.

PCWI DC Creast meter with certification to verify the detector output. You can see the various earths trailing bare wires, earth spikes and having the pipe to actual earth.


There's many different types of earthing available. You should always make sure that the pipe itself or the substrate is thoroughly earthed, standard earth leads, trailing earth leads and capacity of earth mats for pipes that do not have an earth and you need to create an earth. 


Do not earth onto the painted steel. Earth onto the substrate if it's available. If using a trailing earth make sure the substrate is earthed at another location. In this photo where they have clipped the earth onto the painted steel, that's not going to work. 

Before you start the holiday testing project make sure you have on hand the correct probes needed and that they are in good condition to carry out the inspection testing in the correct manner. Make sure that your fine wire bristle probes are in better condition than this one here is. 


This is the range of probes that are available.


Brass strip probes, internal probes, discs, spiral wound internal probes for small bore, external pipeline brushes, half brushes, a full range of pipeline coils and adaptors. Porosity holiday testing, it may be a once off opportunity to carry out the test. Make sure you got it right the first time.

Access for retesting may not be available and to re-establish the conditions to retest may be very costly.


This is some of the scaffolding that is used. Tank internals, exhaust stacks externals, that if you had to re-establish to do a test I think it could be more than costly. Porosity holiday testings at times is seen as something that holds up a project and not a lot of thought or time is put into it. At the end of the day it may be the project's saviour.


A last minute decision to high voltage test these towers, found one tower had a large amount of pinholes right down one side. The reason? Overspray from one spray painter was deposited on the surface of the down wind side and sprayed over by the second painter.

How much time is needed to be allocated to porosity/holiday testing structure and tank linings?

A good starting point is a little less time that it took to apply the final coat. Unless you find a lot of flaws. With tank internals and submerged structures, the surface needs to be 100% tested. Do that with overlaps of the brush strokes so you have no missed areas and you're passing a flaw from one side to the other. For large areas, a small fan brush will not do that.


A small fan brush versus a large brush, well you can see the end result.

On welds, structural steel geometric shapes and textured surfaces, do not use rubber strip probes. Use brass wire strip probes as they follow the contour better. For small areas and bolt holes use a fan brush.


Here's a typical example of using a rubber strip probe in an inappropriate area. Probe travel speed, this should be one metre in four seconds. On welds, structural steel, geometric shapes and textured surfaces, slow the travel speed down and test coming from both different directions.


This is a heavily corroded area and should be tested with a fine wire bristle brush. Only use brass wire strip probes for surfaces like this.

This is a wet sponge tester. A very simple and easy to use instrument. Well, I thought so.

This is a wet sponge pinhole test. He's travelling far too fast. The sponge could not be wet at all. Wet sponge testing is generally carried out quite slowly. Probe speed travel should be one metre for four seconds. Wet sponge low voltage testing, slow down the probe speed and keep the sponge wet. The sponge needs to wet the floor in order to complete the circuit and sound the alarm.

With environmental issues today no-one really needs coating failure as you need to repair. Corroded pitted steel or leaking or ruptured pipelines are a disaster. It's a different world today than what it was a few years ago. Maybe it's time to do a little rethink on this porosity. PCWI Porosity / Holiday detector probes. We manufacture anything you require in this area. Earth leads, extensions, adaptors etc.


Visit our Porosity product page for more information about our porosity detectors and accessories



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