Knowledge Base

Earthing Types for Porosity Holiday Detectors - Video


Porosity Holiday Detectors, grounding and earthing types for differing applications.



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

Porosity and Holiday Detectors. The instruments and support you need for your industry. Detector Earthing for your test application.


PCWI Porosity and Holiday Detectors manufactures a vast range of brushware to suit both the DC pulse and the DC units.


This is some of the brushware that is available with straight brushes, external pipeline brushes, internal brushes, and some very large segment brushes.


Coils are special made to order. The wet sponge unit low voltage tester will only work with a wetted sponge and a direct earth to the substrate. This unit will not work with brass bristle wire brushes.


High voltage detectors a pulse detector in a 20 and a 40kv and a DC direct current and a constant current unit at a 15kv and 30kv. With a vast arrangement of differing earths.


We have 10mt and 15mt trailing earths. There is a bare wire, stainless steel wire, a capacitive earth mat that you can put inside and on the outside of pipes or of capacity earths. With standard earth leads, many lengths available virtually as long as you like.


Before you switch on, let’s first do the Earth thing. Earthing for small and large items.


Always earth the detector to the substrate and then the substrate to ground, this is virtually a double earthing system. It does make a lot of sense because a lot of times small items do not have a lot of mass and need to be earthed a little bit more substantially. Always earth detector and the substrate to ground.


Earthing for wharves and shipping can simply drop the earth leader easily into water. It is also a good idea to put a spike into the concrete or attach it to the rebar and from there earth onto the ship - it just adds a little stability.


Welded plastic sheeting tank liners. Always earth detector to the backing of the liner and to ground. You weld above concrete, wet sand, compacted sand mainly for liners in dams etc. You can put a metallic strip behind the weld. You can you clip on to that. Make sure you have a good ground to earth.


You can also maybe even a tank bottom. You can float it in a little bit of water and get inside the tank on top of the plastic and test it that way. The water actually becomes like a substrate provided that you have an earth lead attached to it.


Concrete structures. We can test coatings on concrete structures with higher voltages, tank liners, coated walls, coated floors, the back of retainer walls and wet areas in multistorey buildings.


You can test coatings on concrete by putting a spike on the concrete and attaching the earth onto the rebar and wet the area to increase the contact area to give you a slightly better earth.


Pipes internals, externals always earth the detectors of the substrate and the ground. You can have various sorts of structures above the ground. An earth exists where the substrate is not available.


You have the trailing, what we call a trailing is a bare wire that is pulled along somewhere along the line the substrate of the pipe or the structure needs to be earth as generally the earth is carried across from one area to another especially welded pipelines.


If they are slip jointed maybe each section does not have an earth and you need to cross check that. What you can do with pipes that are slipped jointed that have rubber over rings etc. you can put a conductive rubber mat on the outside or in the inside if you are in the inside you can have what is called a capacitive earth called a carbonised rubber mat. It can be a sheet of tin, actually, as it will do the same thing and the earth may not be available to hook on to the pipe and the pipe may be that it is just not earthed from anywhere. You need to cross check this to find what you are looking for in this section.


Earthing depends on contact, moisture and conductivity. Trailing earth lead lines may not always work. Ground spikes must be wetted in order for them to work. You get some very wet areas, dry areas, damp maybe and exceptional dry areas. Trailing earth lines in some of these cases may not work and you must be able to ground spike. Some very dry sand and below that there are some coarse broken up rock and trailing earths will lay on top.


You will not have enough contact area and you will get very poor earthing in these areas. They are not suitable for trailing earths and you have to earth the ground spike and you need to wet the ground spike. 

Extra-long earth leads. Try and keep them as short as possible as they run along the ground or along the tank internals they will pick up capacity of earthing as well. So although you might have it clipped on to the substrate a long way away it will pick up a little extra earthing as it travels along the ground.


Trailing capacity of earth. If you have got the pipes sitting on insulating wooden supports you need to clip on to the substrate of the pipes or the structure. Once it has got insulated wood support and there is no contact between the substrate and the ground, the trailing earth will not work in this situation.

With the environmental issues today no one really needs coating failure as you need to repair or corroded pitted steels or leaking and ruptured pipelines are a disaster. It’s a different world today. Maybe it is to do a little rethink on this on this porosity detectors.

PCWI Porosity/Holiday Detector Probes will manufacture anything you require in this area. Earth leads, extensions, adaptors etc. Contact


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



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