Coatings and linings are used across many industries to protect structural steel, concrete, and other materials from corrosion. To perform properly, they must be free of defects or discontinuities that expose the substrate beneath. Areas of thin or missing coating, called ‘pinholes’ or ‘holidays’, are often invisible to the naked eye, and are near-impossible to detect without proper instrumentation.
Holiday detection is a necessary step in identifying these areas of thin or missing coating as they can become foci for corrosion and drastically reduce the life of a protective coating system.
The instrument used to detect these defects depends on the thickness of the applied coating. The PosiTest LPD Low-voltage Pinhole Detector is ideal for finding defects in coatings less than 500 microns or 20 mils thick by emitting voltages below 100 volts through a moistened sponge.
But for coatings in excess of 500 microns, a high-voltage detector is needed. Instead of a moistened sponge, a charged conductive brush or spring electrode is used.
The principle of operation for high-voltage holiday detectors is similar to low-voltage detectors. The charged electrode is passed over the coating, and when a holiday is encountered current flows from the electrode into the substrate below. The current returns to the detector through the ground wire, completing the circuit and triggering audible and visible alarms.
DeFelsko offers two high voltage holiday detectors—the PosiTest HHD features a stick design and uses pulse DC technology to detect flaws. The PosiTest HHD C has a wand design and uses continuous DC to detect flaws. Both models feature adjustable voltage, built-in certified voltmeters, and compatibility with nearly all existing (competitive) electrodes.
The PosiTest HHD emits a precise pulse of high-voltage current 30 times per second. This technology is easy to ground, and reduces the possibility of the exterior of the object becoming charged. The advanced circuitry is capable of maintaining a precise voltage output over the full range of 0.5-35 kiloVolts in a single instrument. For more information check out the full PosiTest HHD instructional video.
The PosiTest HHD C High voltage Holiday Detector uses continuous DC to detect holidays in coatings. It operates at a similar voltage range as High voltage Pulse holiday detectors, with the added benefit of being light, compact, one-handed instruments. Unlike some continuous DC models, the PosiTest HHD C does not require carrying a separate shoulder battery bag. All of the electronics fit neatly within the wand eliminating the need for a separate power source.
All PosiTest HHD Models are compatible with a range of quality electrodes, including steel rolling springs for pipes up to 2.4 meters or 8 feet in diameter and a selection of brushes up to 1.2 meters or 4 feet in length. All connectors are manufactured from stainless steel, aluminum or neoprene to be corrosion resistant, durable, and lightweight—with no tools required for electrode changes. Adaptors for all major competitive electrodes are available for connecting existing spring and brush electrodes from nearly any brand of holiday detector. The PosiTest HHD series is directly compatible with DeFelsko and Spy electrodes. To attach the desired electrode simply use the knurled thumbscrew to secure.
An extension rod is also available for the PosiTest HHD C for detection on floors and hard-to-reach areas.
The PosiTest HHD C conforms to national and international standards for holiday detection including ISO, ASTM, and NACE for holiday detection.
The PosiTest HHD C’s intuitive menu interface makes holiday detection simple. Simply input the coating thickness to automatically calculate the required test voltage. To begin testing, simply screw in the heavy-duty ground connector, and find a suitable ground. Connecting the heavy-duty clip to a bare uncoated area on the substrate is required.
Press the power button to turn the PosiTest HHD C on. The set voltage is shown on the backlit display, and the icon-based menu can be accessed at the touch of a button to change settings such as the test voltage. The voltage can be adjusted in 10 volt increments between 500 and 1,000 volts, and in 100 volt increments between 1 and 30 kilovolts. Press the menu button to accept and exit.
The PosiTest HHD C has two primary operating modes, Standby Mode and Detection Mode. In Standby Mode, the detector is powered up but not generating a high voltage. When the trigger is activated the instrument enters Detection Mode, and the detector actively sends out voltage and listening for a return signal. The lightning bolt icon will appear at the bottom of the display, and the instrument will emit a tick sound.
Prior to testing, it is a best practice to verify the operation of the instrument by putting the instrument into detection mode and passing the electrode over a known holiday in the part being tested, and ensuring that the alarm activates. This ensures that the instrument is properly configured and grounded. The PosiTest HHD C is ready to begin testing.
Place the electrode on the surface being tested. Move the electrode over the coated surface at a travel speed not to exceed 0.3 meter per second or 1 foot per second, to locate defects. If a holiday is detected, the PosiTest HHD C will activate the strobe and audio alarm.
Before removing the detector from the surface, release the trigger to deactivate the high voltage output and return the PosiTest HHD C to Standby Mode.
The durable PosiTest HHD C features a shock-absorbent housing purpose built for tough pipeline and manufacturing environments. Powerful, lightweight Li-ion batteries fit neatly within the compact wand handle eliminating the need for a separate battery box–reducing weight and operator fatigue. It weighs under 2 pounds or 1 kilogram and is designed to be used comfortably all day.
The PosiTest HHD C has a built-in certified voltmeter ideal which continually regulates the operating voltage. A separate certified voltmeter is available for verifying all continuous DC holiday detectors in the range of 500 to 30,000 volts, if required.
Ordering is easy. The PosiTest HHD C kit includes everything needed for testing — the instrument, ground (earth) cable with ground clip, smart charger with universal AC voltage input, stainless steel fan brush, durable hard shell case, and a long form certificate of calibration.
The PosiTest HHD C is the simple, durable, and accurate way to find defects, pinholes, and holidays in a coating system.
For over fifty years, DeFelsko has been a leader in inspection equipment, manufacturing simple, durable and accurate gages. Backed by DeFelsko’s renowned quality, customer service and exceptional two-year warranty, the PosiTest HHD C is the ideal choice for holiday detection.