Read about START-PROF pipe stress analysis software
If angular valve has equal legs, then it can be modeled using ordinary valve element. Just put it into node between two pipes. Pipes can have a different diameter. One half of valve length will be placed through first pipe direction and one half through another.
If valve have unequal leg lengths, then it can be modeled using rigid elements. The total weight of rigid elements should be equal to valve weight. To model temperature expansion the temperature and material should be specified in rigid element. Also flanges can be added into end nodes of valve to check leakage.
Three-way valve can be modeled just using 3 rigid elements.
START-PROF does not allow four elements crossing in one node. A cross can be modeled by moving the node of one of connecting elements by 1mm. Three-way valve can be modeled using 4 rigid elements. The total weight of rigid elements should be equal to valve weight.
Heavy wheel or drive can be modeled as node weight load at the drive center of gravity. This mass should be connected to valve using rigid elements with zero weight to consider eccentricity. Proper modeling of drive eccentricity is especially important for seismic analysis of piping systems, because the eccentric mass will produce a great additional torsion and bending moments on the piping system.