Singapore’s STX OSV Holdings (STX OSV) has confirmed an order for two platform supply vessels (PSVs) from Island Offshore.

Each of the 3,800dwt vessels will have a length of 84.3m, a beam of 17m and will be based on Rolls Royce’s UT 717 CD design.

The two vessels are expected to be delivered in the third and fourth quarter of 2013, respectively.

The contracts were originally signed on 30 October 2011 for four PSVs with a combined value of NOK1bn ($177.38m).

The remaining two similar vessel contracts are likely to become effective in January 2012 and expected to be delivered in the first quarter of 2014.

STX OSV Braila in Romania will deliver the hulls of the vessels, which are to be delivered from STX OSV Brevik in Norway.

Earlier in 2011, the Singapore shipbuilder won a $138.19m (NOK750m) contract from Island Offshore to build two platform supply vessels (PSV), which were based on Rolls Royce’s UT 776 CD design.

PSV pair, which had an overall length of 96.8m with a beam of 20m and a dead weight of 4,800dwt, is expected to be delivered in the first and third quarters of 2013, respectively.

The company said the contract for the second vessel was subject to certain conditions being fulfilled before the end of third quarter of 2011.

In September 2010, Island Offshore ordered two LNG-powered PSVs worth NOK900m ($144m) at STX Norway Offshore.

The South Korean shipbuilding company said the vessels had a displacement capacity of 4,750t and were scheduled to be delivered in the second and third quarters of 2012.

The PSVs developed by STX OSV to be delivered to Island Offshore in third and fourth quarter of 2013.