A good place to start is the PETROLEUM ENGINEERING HANDBOOK by Brady. It shows step by step proc for sep sizing. If not the www.spe.org electronic library may be off help..If not then try a service Co, like Hanover in Houston..
Hope that helps..
Dummy Valves are utilized in production tbg for the purposes of having a plug or blank till the operator knows the flow conditions and surface components to size down hole GLVs.