An IP67 load cell is tested for 30 minutes at 1 m depth, in fresh water, at room temperature. A washdown area in a food plant is none of those things: it is chlorinated water at 60 °C, directed at pressure, cycling every hour. The rating is a floor, not a guarantee.
How water gets in
Three paths dominate: the cable entry, the gauge area under the potting, and the breathing vent on sealed cells. Cable entry failures come from a gland that is tightened onto the jacket rather than the shield, letting water track along the wires. Potting failures come from thermal cycling that opens a path at the adhesive interface.
Specifying for wet service
Ask for IP68 or IP69K where jet washing is used, a welded stainless body rather than a glued cover, and a cable entry with a proper compression seal. On cells that breathe, mount the vent with a desiccant cartridge and change it on a schedule. For food areas, check that the materials survive the cleaning chemicals, not just the water.
Diagnosing ingress
Insulation resistance between bridge and body, measured at 50 V, is the fastest indicator. A healthy cell reads above 5000 Mohm; a few hundred Mohm means moisture is present and the cell will drift with temperature. Measure before condemning a cell that reads erratically in humid weather.
Kevin Huang