How to choose the sphere in the middle of the rubber expansion joint?

The first thing to consider is the size, only if the size is suitable, the installation will be successful.
Determine the material of the shell and internal parts of the selected rubber joint according to the medium of the pipeline, medium temperature, working pressure and working temperature.
Determine the connection mode of rubber joints: double sphere rubber joints, single sphere rubber joints, clamp type rubber joints, threaded rubber joints, etc.
Determine the parameters of rubber soft joints: for rubber soft joints, first determine the allowable flow resistance, discharge volume, back pressure, etc. according to different requirements, then determine the nominal diameter of the pipe and the valve seat hole.