MD80 CREW HAD ENG FAILURE ON ARR AT STL.

Narrative

INBOUND FROM ICT THE MAJORITY OF THE FLT WENT NORMAL. AS WE NEARED FORESTELL VOR WITH THE ENGS AT FLT IDLE; THERE WAS A LOUD BANG FROM THE REAR OF THE ACFT; AND THEN A CONTINUOUS GRINDING SOUND. A SCAN OF THE COCKPIT INSTS GAVE NO INDICATION OF THE PROB. A FLT ATTENDANT BROUGHT THE NEWS OF THE SOUND WAS EMANATING FROM THE R SIDE OF THE ACFT. AT THAT TIME; IN AN EFFORT TO IDENT THE ENG; I INCREASED PWR TO THE L ENG WITH NO SOUND OUT OF THE ORDINARY. I THEN INCREASED PWR TO THE R ENG. THERE WAS A NOTICEABLE INCREASE IN THE GRINDING OR ENG ROUGHNESS. RETURNED THE ENG TO FLT IDLE. I ASKED THE FO TO REVIEW THE QRH WITH ME AND CALLED THE L1 TO THE COCKPIT FOR INSTRUCTIONS. I MADE A QUICK CABIN ANNOUNCEMENT TO THE PAX AS TO WHAT WAS TRANSPIRING. AS WE NEARED THE ARPT; ATC ADVISED THAT THEY WERE CHANGING RWY LNDG DIRECTIONS AND THIS WOULD CAUSE SOME DELAY IN LNDG. AT THAT TIME; I DECLARED AN EMER SO AS TO EXPEDITE OUR LNDG. WE WERE GIVEN PRIORITY AND CLRED TO LAND ON RWY 12R. THE LNDG WAS UNEVENTFUL AND NORMAL. AFTER A QUICK INSPECTION BY THE GND EMER PERSONNEL; WE TAXIED TO THE GATE WHERE THE MECHS WERE WAITING TO INSPECT THE ACFT. THE PAX DEPLANED WITH NO COMPLAINTS OR REQUESTS FOR ASSISTANCE. THE MECHS DISCOVERED METAL PARTIALS IN THE R ENG OIL FILTER. THEIR COMMENTS TO US WERE THAT OUR ACTIONS SAVED THE ENG FROM SELF-DESTRUCTING.