We have refrigeration package of NH3 as refrigerant, from the last 6 month we facing the problem of oil carry over to Chiller and KOD. we have to continuous drain out oil from the chiller and KOD while receiver level is constant in LT and LG both. NH3 package super feed currently isolated as it is suspected that might be there is a leak in super feed coils since its pressure equivalent to receiver pressure. but the LT of super feed is very erratic,a DP type LT which has been attended many times but problem still as it is. please suggest me what type of LT to be provided for the super feed level and what can be the reason of oil carry over to chiller and KOD.