Hello Anadhan
You didn't mention if its working in scanerio if it found the existing Ibase with same ship to party .
Going thru ur code. you made a check
READ TABLE lt_ib_head_tab INTO ls_ib_head_tab INDEX 1.
IF sy-subrc = 0 .
if it found the ibase then only it should attach the equipment to the ibase.
Code is missing for the scenario where it does not find the existing ibase with desired ship to party.
Regards
Naresh