India's Rana finishes 33rd; Heffernan clinches gold
Rana timed 3 hours 58 minutes and 20 seconds to finish the gruelling event. His compatriot Sandeep Kumar, who was 45th at the half-way mark, was disqualified shortly afterwards.
Rana had clocked a national record of 3:56:48 while coming 36th in the London Olympics last year.
Ireland's Robert Heffernan won the gold medal after a grim battle against his Russian and Australian rivals. It was his country's first World Champioships gold in 30 years.
Heffernan clocked 3:37:56 to come ahead of Mickhail Ryzhov of Russia and Jared Tallent of Australia. Ryzhov clocked 3:38:58 and Tallent timed 3:40:03.
Kenya's Asbel Kiprop, in sizzling form this season, led the qualifiers into the semifinals of the men's 1500 metres in a time of 3:38.15 while Ethiopian Meseret Defar, the Olympic champion, safely entered the final of the women's 5000 metres, timing 15:22.94.
In long jump qualifying, Olympic champion Greg Rutherford of Britain crashed out while season's leaders Alexander Menkov of Russia and Luis Rivera of Mexico advanced after a bit of a struggle.
Rutherford, who has been struggling with a hamstring injury, could manage only 7.87 metres on the day.
Four-time champion Dwight Phillips, competing in his seventh World Championships, also made it through with a season's best of 7.95 metres.
World record holder Betty Heidler of Germany bowed out in the qualifying round itself, finishing 18th. Heidler, who was unbeaten in eight competitions this season, had a best of 68.83 on the day.
Results: Men: 50km walk: Robert Heffernan (Ireland) 3:37:56, 1; Mikhail Ryzhov (Russia) 3:38:58, 2; Jared Tallent (Australia) 3:40:03.