Lifeimi Mafi gave them the lead with some neat footwork that led to an 8th minute try and he repeated the dose thirty minutes later for a second try that replaceement out-half Eoghan Hickey converted for a 12-3 lead.
In injury time Sweeney threw his side a lifeline with a well taken drop-goal but by then Munster were without Manning who had retired with a shoulder injury. They were also reduced to 14 after Andy Kyriacou had been yellow carded.
Shortly after the restart Munster lost John O'Sullivan with a knee injury and soon after that lost the lead when Ringer scored his try. But winning this game still looked well within the Munster compass and they should really have regained the lead in the 64th minute when awarded a penalty but Hickey was narrowly wide from in front of the posts.
With nine minutes of normal time remaining Munster were again reduced to fourteen when Donnacha Ryan was yellow carded for coming round a ruck and Sweeney made no mistake with the resultant kick. Just on the stroke of full-time he ended any hope of Munster's snatching a dramatic victory when he landed his third successful penalty.
Munster: C Cullen; A Horgan, L Mafi, T Halstead ( M Lawlor 59 min) I Dowling; J Manning (E Hickey 30 min) (B O'Meara 68 min), T O'Leary; M Horan (F Pucciariello 55 min), A Kyriacou, T Buckley (E McGovern); D Ryan, M O'Driscoll; C Wyatt (J Coughlan 57 min) J O'Sullivan (P O'Connell 46 min), A Foley capt.