Semi Welded Plate Heat Exchanger

A semi-welded plate heat exchanger uses plates joined together in pairs by a continuous laser or TIG weld around the port and perimeter, forming a fully welded channel on one fluid circuit. The other circuit remains sealed conventionally with elastomer gaskets, so the welded plate-pairs stack together with standard gaskets between each pair, just as in a fully gasketed unit.

This hybrid construction exists because some fluids, most commonly ammonia and other refrigerants, are not chemically compatible with standard gasket materials, or the application cannot tolerate any risk of a gasket seal failing on that circuit. Welding that side removes the gasket entirely from contact with the aggressive fluid, while the non-aggressive side keeps a gasketed seal that is easy to open, inspect and clean.

Because only one circuit is welded, a semi-welded plate heat exchanger still opens for inspection and cleaning of the gasketed side, and the frame can still be re-plated if needed. This keeps serviceability much closer to a standard gasketed unit than a fully welded design, while still giving the aggressive-media circuit the same leak security as a welded plate heat exchanger.

Semi-welded construction is the standard choice for ammonia (NH3) evaporators and condensers, as ammonia attacks copper and most elastomer gaskets over time. It is equally suited to other refrigerants and to process duties where one fluid is corrosive, toxic, or gasket-incompatible but the other side is ordinary water or process fluid.

SRJ manufactures semi-welded plates on the same press tooling used for our standard gasketed range, so port geometry and plate corrugation match the equivalent gasketed model. Weld quality on every plate pair is helium leak tested before the unit is assembled and pressure tested, ensuring the welded circuit is fully leak-tight before dispatch.