Four-way fittings are used for pipe and pipe connection components. Also known as four-way pipe fittings or four-way fittings, they are used at the main pipeline where a branch pipeline is to be connected. Four-way fittings come in both equal and unequal sizes; equal-size four-way fittings have all branches with the same diameter; unequal-size four-way fittings have the main pipeline branches with the same size, while the branch pipeline branches have a smaller diameter. Four-way fittings are a type of pipe fitting used at pipeline branch points. The hydraulic expansion process of a four-way fitting involves using a hydraulic press to inject liquid into a pipe blank of the same diameter as the four-way fitting. The press's two horizontal cylinders synchronize to move and compress the pipe blank. As the blank is compressed, its volume decreases, causing the liquid inside to increase in pressure. When the pressure reaches the level required to expand the branch of the four-way fitting, the metal material flows and expands into the branch under the combined pressure of the side cylinders and the liquid pressure within the blank.