The 19,900-cbm JBU Opal (built 2009), JBU Onyx (built 2008) and JBU Sapphire (built 2009) will join in May, June and July this year.
The sisters were built at Kitanihon Shipyard in Japan.
The deal swells the pool to 16 ships, six of which are newbuildings due in 2016 and 2017.
Siva has two other chemical carriers of a similar size that are not in the pool so far.
