Eleven minutes later that cushion was stretched to 12 points as a well-weighted cross-kick in the Bulls red zone from Francis found Duffie, who was over for a simple try.
The missed conversion was Francis’ last act as West replaced him at fly-half and relished the closing stages.
Despite being a man down when flanker Jimmy Tupou was binned for a neck roll, the Blues cut loose with West spotting a gap in the 22 and promptly slicing through it.
That pushed the Blues into a 24-7 lead and also put the bonus point on the board with 13 minutes remaining.
The Blues eyed more though and made sure of the maximum haul with further crossings from replacement hooker Moulds and wing Nanai adding the gloss to a comfortable win that puts them on 11 points from five games.
Tries: Pulu, Duffie 2, West, Moulds, Nanai
Cons: Francis 2, West 2
Yellow Card: Tupou
Tries: Gqoboko, Paige
Cons: Pollard, Schoeman
Blues: 15 Michael Collins, 14 Matt Duffie, 13 Rieko Ioane, 12 George Moala, 11 Melani Nanai, 10 Piers Francis, 9 Augustine Pulu, 8 Jerome Kaino, 7 Blake Gibson, 6 Jimmy Tupou, 5 Patrick Tuipulotu, 4 Gerard Cowley-Tuioti, 3 Charlie Faumuina, 2 James Parsons (c), 1 Pauliasi Manu
Replacements: 16 Matt Moulds, 17 Ofa Tu’ungafasi, 18 Sione Mafileo, 19 Akira Ioane, 20 Murphy Taramai, 21 Sam Nock, 22 Ihaia West, 23 TJ Faiane
Bulls: 15 Warrick Gelant, 14 Travis Ismaiel, 13 Jesse Kriel, 12 Jan Serfontein, 11 Jamba Ulengo, 10 Handré Pollard, 9 Piet van Zyl, 8 Hanro Liebenberg, 7 Nick de Jager, 6 Ruan Steenkamp, 5 Lood de Jager, 4 Jason Jenkins, 3 Trevor Nyakane, 2 Adriaan Strauss (c), 1 Lizo Gqoboko
Replacements: 16 Jaco Visagie, 17 Pierre Schoeman, 18 RG Snyman, 19 Jannes Kirsten, 20 Rudy Paige, 21 Tian Schoeman, 22 Burger Odendaal, 23 John-Roy Jenkinson