A cladding can look perfect and still have a pinhole. The holiday spark test runs a high-voltage wand over the surface, and any pinhole sparks. This catches the defects that visual inspection misses, before the heater leaves the shop or returns to service.
The test voltage is chosen for the film thickness. The coated heater is spark-tested over the full surface, and any pinhole is repaired and re-tested. Material-selection service specifies the test voltage. At each batch, the test is recorded. Procurement requires the holiday-test report.
The holiday test is repeated at each outage. The coating is re-sparked to check for new pinholes from wear or damage. The smooth surface is also inspected visually. The result is a verified, defect-free heater.
Plants that skipped the holiday test found pinholes in service. The test catches the pinhole before it reaches the process. The result is a cladding that is verified, not assumed, and the field touch-up kit repairs any new holiday found at each turnaround.
Visual inspection cannot see a pinhole. A cladded heater can look perfect on the rack and still carry a microscopic holiday that will become a pit in service. The holiday spark test solves this by running a high-voltage wand over the surface; any pinhole sparks. The voltage is chosen for the film thickness, so the test is sensitive without false-firing on the texture. The coated heater is spark-tested over the full surface at the factory, every pinhole is repaired and re-tested, and the report travels with the heater. Material-selection service specifies the test voltage, and procurement requires the holiday report as a condition of acceptance. The test is not a one-time event: at each outage, the film is re-sparked to catch new pinholes from wear, fretting or impact. The smooth surface is also inspected visually. Plants that skipped the receipt test found shipping or fabrication damage in service, and the field touch-up kit repairs whatever the wand finds. The result is a cladding that is verified on every batch and every turnaround, rather than assumed good, and the field program keeps it defect-free for life.
The receipt test also verifies the film is dry and clean, because a damp film gives false sparks. At each batch, the report is filed. The material-selection service requires the report as acceptance. The result is a cladding that is verified before installation and re-verified at each turnaround, because the holiday wand catches the pinhole that the eye cannot see.
The holiday report travels with the heater to the field. The material-selection service files it. The result is a verified cladding, because the pinhole is caught at the factory, in the field and at every turnaround, and the touch-up kit repairs whatever the wand finds.
The controller also ventilates the tank headspace, which reduces the acid mist that condenses on the upper tube. The smooth cladding surface sheds the condensed acid, and the second coat on the upper length brings the film to a thicker gauge where the mist is worst. Procurement specifies the double-coated upper length on the drawing. At each outage, the upper tube is inspected for blistering and the thickness measured. Plants that had external acid-mist corrosion on the upper tube switched to a second coat. The result is a heater that resists the acid environment both inside and above the tank.
