sohrab t,
Your question is vague, we will need more information in-able to give you any help.
You asked:
"what is the relationship between pig size and bend or elbow size in pipeline"
What Types of Pigs will you be using (It is common for a Pipeline Company to use more than on type of Pig in the overall operation of a Pipeline.
You need to share the following information"
Pig Types = ?
Pipe Size = ?
Pipe Material = ?
Pipe Wall thickness = ?
Commodity = ?
Pipeline Location = ?
Above Ground or Underground Installation = ?
Sometimes its possible to do all the right things and still get bad results