Manifold design

So far with the information you provide I can only tell you the following things.

1. Valves size (in inches) will depend of the pipe diameters (in inches) and this depends of some other factors.

2. The number of oultlets basicly depends of the number of separators you have in your field. Normally you have one test separator and one or two production separators

3. In a rig?? You mean an oil pipeline that connects one production station with other?? If that then you have 2 options a pumping station, where you´ll give preassure to the flow or a reduction station where you will reduce the preassure in the line. The number of these stations would depend of the lenght of your line and the topography of the terrain you´ll cross}

Hope you find it useful