IOCL has shut its only naphtha cracker and half of its Panipat refinery since early this month for maintenance, head of refineries S M Vaidya said on Tuesday.IOCL shut a naphtha cracker which can produce around 800,000 tonnes per year (tpy) of ethylene and it has also idled 50% of its 300,000 barrel per day (bpd) refinery in Panipat.The units will resume operations on Sept. 25 In a major move the unit is to further expand its capacity of the cracker to 1.1 million tpy in 2021/2022.