All rounder Mannan Sharma (68 batting) also got his second fifty in as many matches.
Rana and Rawat carried on from where they had left off against Assam in the opening encounter after Delhi's top three Gautam Gambhir (2), Unmukt Chand (11) and Dhruv Shorey (16) were out cheaply with scoreboard reading 44.
Nitish, who faced 145 balls hit 12 boundaries as he again peppered the off-side field with cut shots and some flowing drives on the on-side.
Himmat, in fact came down the track to hit off-spinner Avinash Yadav in the second tier of the dressing room for a big six.
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However Himmat missed a chance to score a debut half century when he was caught behind trying to cut Avinash.
After his impressive debut, Rawat looked more assured alongside Rana, playing both cuts and drives on the off-side.
As Nitish was looking good for his second hundred, he came down the track to a flighted delivery from Shivakant Shukla to be stumped 11 short of three figure mark.
Rawat again showed good temperament as he faced 152 balls before Anureet Singh (3/71) got him at the fag end of the day.
Group A Brief Scores: Delhi 318/6 (Nitish Rana 89, Anuj Rawat 74, Mannan Sharma 68 batting, Anureet Singh 3/71) vs Railways.
At Mysore: Assam 144 in 59.1 overs (Gokul Sharma 55; Shreyas Gopal 3/43). Karnataka 77/0 in 30 overs (Ravikumar Samarth 47 batting , Mayank Agarwal 26 batting).
At Hyderabad: Hyderabad versus Uttar Pradesh. No play on day one.
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