These are used when the primary problem is a large axial movement. Materials can be selected to accommodate high temperatures and pressures. Design details include selection of packing and seals and perhaps resistance to abrasive solids.

Slip-type expansion joints are made by "telescoping" one pipe within another and sealing them together with packing, which will take the temperature and pressure while allowing large movement in the axial direction. If the joint is subjected to forces perpendicular to the pipe, the design is more critical. The photo to the right shows a prototype unit being tested in a load cell to determine the force required to move the joint in the axial direction (down) when another perpendicular force is being applied. The photo below shows a truckload of joints being shipped to a coal-fueled power plant.