Imtiyaz,
In order to do this you need to know a little more about the pipeline, for instance: How much does the line need to lowered?  What service the line is in?  What length of pipe needs to be lowered?
The calculations for the lowereing scheme are fairly simple and are based on the minimum radius that the pipe can handle, taking into consideration its size and grade.  The number of sidebooms to be used is a factor of how long a span the pipe can take, again taking into account its size and grade.  However, it also based on experience in the field, the terrain, and what size sideboom you intend to use.
I'll be glad to help you with this, just ask.

Regards,
ODEM

Thanks odem,
1) Line to be lowered for;
     12" X65  -  1.5 mtrs in trench.
     48" X70  -  2.5 mtrs in trench.
2) Service;
     12" X65  -  Condensate line.
     48" X70  -  Gas Pipeline.
3) Length of Pipe to be lowered;
     12" X65  -  1.5 to 2 km
     48" X70  -  1.0 km
4) Side Boom;
     12" X65  -  CAT 571
     48" X70  -  CAT 583 or 589

Radius allowed is 500D.
In advance thanks for the effort.
Waiting for your posting.
Imtiyaz

Take care :)

Chapter 11 of Troitsky's "Tubular Steel Structures" is on Underwater Pipelines.
$24 from https://ssl.lincolnelectric.com/foundation/ Such a deal!!

Thanks