Penfield Marine continues a gradual build-up of its aframax pool with three tankers scheduled to deliver this week.

The additions will build its aframax fleet to 15 vessels contributed by nine partners, up by half from 10 tankers and six members since the start of the summer.

The increase fits Penfield’s goal of controlled growth on the aframax side while keeping its pool of panamaxes ­relatively stable between 25 and 30 vessels, chief executive Tim Brennan said this week.

“As I mentioned [in May], we want to have sustained slow growth in the aframax pool,” he said.