DeFelsko PosiTest LPD Accessory Pack LPDACCPK
Includes adaptable sponge hardware and accessories to convert the PosiTest LPD Basic Kit into a PosiTest LPD Complete Kit in a hardshell carrying case.
Adaptable Sponge Hardware
Low voltage Pinhole Detector for Metal and Concrete Substrates
Detects holidays, pinholes and other discontinuities in coatings on metal and concrete substrates.
GroundSense visibly reassures the user that the...
A pinhole detector is a non‐destructive instrument for detecting discontinuities in a coating system including pinholes, cracks and thin spots. Other names include porosity detector, continuity tester, sponge tester and holiday detector.
There are two types of pinhole detectors, low voltage (wet sponge) and high voltage (spark tester). Low voltage detectors, like the PosiTest LPD, are typically used on coating systems less than 500 µm (20 mils) thick. High voltage spark testers operate at voltages up to 35,000V which can seriously harm the operator and damage the coating if the test is not correctly conducted. They tend to be more expensive and more complex than low‐voltage pinhole detectors.
A low‐voltage pinhole test is performed by moving a moistened, electrified sponge over a non‐conductive coating applied to a conductive substrate. The instrument is 'grounded’ or ‘earthed’ to the conductive substrate, typically by clamping onto an uncoated area. When the coating is continuous and no defects are present, electricity is unable to pass from the sponge to the substrate through the non‐conductive coating. But when the electrified sponge encounters a flaw in the coating, electricity is able to flow into the substrate and travel back to the instrument through the ground wire, completing the circuit and setting off the audible and visible alarms.
When measuring coating thickness, concrete is not considered a ‘conductive’ substrate, as it is much less conductive than metal. However, concrete is still slightly conductive, and can carry enough current to allow low‐voltage pinhole detectors to function. Therefore, for the purposes of low‐voltage pinhole detection, concrete is considered a ‘conductive’ substrate.
The challenge when conducting low‐voltage pinhole testing on concrete is to ensure the instrument is properly grounded. If there is exposed rebar or metal protruding from the concrete, this is the easiest solution. An alternative is to drive a metal rod (or piece of rebar) into the ground nearby the concrete to at least the depth of the slab, relying on the earth to conduct the electric current between the rod and the slab.
The PosiTest LPD has been designed as a fully customizable unit and offers a number of features not typically found in other competitive instruments.
Sometimes pinholes are so miniscule that water has difficulty reaching the conductive substrate underneath, especially on thicker coatings when the water must penetrate further into a pinhole to reach the substrate. In these instances, inspectors will use a surfactant (wetting agent) to lower the surface tension of the water, allowing the solution to better penetrate the pinhole.