DLF has max of 2.0 for a single application of an impulse load
and you say
iam Doing slug analysis (Impluse loading)
without mentioning the word "single".
Maybe you would progress analyzing the discussions in these threads:
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=80 and
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=43370 and in many others that you can find/ by searching through this forum.