Leak Testing & Inspection

Pressurize one circuit with the other drained and its connections open, then watch the open side for liquid. Any flow there means a breach between circuits, almost always a hole or crack in a plate. Pinholes to small to show during a short hold can be traced afterward with dye penetrant on the opened plates.

From the design pressure on the nameplate and the code the unit was built to, not from whatever the plant system happens to run at. Going beyond the documented test pressure can distort plates or push a gasket out of its groove. Hold each side long enough for the gauge to settle, and record the pressure, hold time and result against the serial number.

Fine cracks and pinholes that pass so little fluid they never register on a gauge. Penetrant on a clean, opened plate shows them as colored lines or dots, usually near the ports or where the corrugations take load. Where mixing the two fluids is unacceptable, such as potable water or food product against a coolant, it is worth running on every plate at major services.

Log each plate by its position in the pack along with what you found, from pitting and cracks to thinning and deposits. Photographs keyed to those position numbers turn the next inspection into a comparison instead of a fresh look. Over a few openings the record shows whether damage is spreading, holding steady or confined to one region of the pack.

Any time the pack dimension changes, a retest is the only proof the seal has held. Tightening to stop a weep can hide a gasket that has rolled out of its groove, and that gasket then lets go at the next temperature swing. If the weep returns after tightening within the specified range, open the pack and find the cause.