dear sir

you can not use loop in pipeline that ther is pigging on it .
you must use bend with the minimum radius of curvature 7D.
consider we have a pig with mass of M and velocity of V .in the rapid change of direction we have rapid change in direction of velocity vector and change to linier momentom creates large force that may deform the pipeline so for reducing the change in linear momentum we must use bends with large radius of curvature.

suppose that we are pipeline with 200 km lenght between refinery and our user.you can not analyze all of the root.so you must use iterative root (zig zag configuration)that you are assure that the stress and load are within the allowable.

ther are some procedure of design of pipe line in the IPS STANDARD
(iranian petrolume standard,you can download it from http://WWW.NIOC.COM)

best regards
a.sadeghabadi