Aug 2 (Reuters) - Rio Tinto (LON:RIO) Ltd RIO.AX
* HY underlying earnings $ 3,941 million versus $1,563 million a year ago
* HY net earnings $3,305 million versus $1,713 million a year ago
* HY sales revenues of $19.3 billion, $3.8 billion higher than 2016 first half
* Declared interim dividend of 110 us cents per share, equivalent to $2.0 billion
* Capital expenditure expected to remain at around $5.0 billion in 2017 and around $5.5 billion in each of 2018 and 2019
* As at HY reduced net debt by $2.0 billion to $7.6 billion
* "Production guidance is unchanged from Q2 operations review"
* Says an increased share buy-back of $1.0 billion in Rio Tinto plc shares by end of 2017.
* Effective tax rate on underlying earnings of approximately 30 per cent expected in 2017
* Heavy rainfall in Australia impacted volumes for iron ore and coking coal, while lower head grades at Oyu Tolgoi led to reduced copper volumes
* "Expects total cash returns to shareholders over longer term to be in range of 40 to 60 percent of underlying earnings in aggregate through cycle"
* Achieved $8.2 billion pre-tax in total operating cash cost improvements and reductions in exploration and evaluation expenditure compared with 2012 base
* Expects total cash returns to shareholders over longer term to be in a range of 40 to 60 per cent of underlying earnings in aggregate through cycle
* Expects Rio Tinto Limited to be in a position to pay fully franked dividends for foreseeable future
* Announces cash generation of $6.3 billion and cash returns to shareholders of $3.0 billion
* Expects additional cumulative free cash flow of $5.0 billion from 2017 to end of 2021 from productivity improvements