It is also used to set tubes prior to welding and to flare boiler tubes. Water pressure from an air driven pumping system is intensified to the desired high pressure. It is transmitted through a small bore, flexible high pressure tube to a lightweight hand-held mandrel holder. A mandrel, which latches into the mandrel holder, directs the pressure to the inside diameter of the tube and is held within an accurately prescribed pressure zone. Pressure is contained within the expanding tube by a soft elastic seal which is supported by a patented elastic backup and an expanding segmented steel ring.
Pressure is applied over the full length of the joint in one step.
The pressure zone is accurately adjusted which reduces the damaging crevices at the edges of the tube sheet. Stress, crevice corrosion, and metallurgical changes are thus minimized. Direct hydraulic expansion with pure water produce clean joints. Lubricant is not forced into the tube surface, and there is no surface flaking or spalling inside the tube. A smooth transition from expanded to unexpanded areas, along with no change in tube material properties, greatly reduces strain hardening, tube fatigue and stress induced corrosion cracking.