A B737 FLC EXCEEDS THE SPD LIMIT FOR FLAP EXTENSION FROM THE 5 DEG POS TO THE 10 DEG POS 10 NM S OF DEN; CO.

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LOCATION: ILS RWY 35L DEN. DEPARTED MIA WITH KNOWN WX PROBS AT DEN. OPS NORMAL ENRTE; ALL CONTINGENCIES COVERED. WE REVIEWED ALT WX; RESTR CAPT'S MINIMUMS; HOLDING OPTIONS; ETC. DEN ATIS WAS CALLING RVR; LLWS; AND MICROBURST ALERTS. WE SET UP FOR RWY 35L ILS. APCH WAS CHANGED TWICE; FINALLY SETTLED ON RWY 35L ILS. FLT PLANNED FOR DANDD 3 ARR; SENT TO LAMAR TO HOLD. HELD FOR 15 MINS; THEN VECTORED TO PUEBLO FOR THE LARKS 3. VECTORED OFF THE ARR TWICE FOR TFC SEQUENCE. APCH DSNDED US TO 11000 FT THEN 10000 FT ON A 280 DEG HDG THROUGH THE LOC; 210 KTS; FLAPS 5 DEGS. WE WERE GIVEN A 330 DEG HDG TO INTERCEPT RWY 35L LOC. THE ACFT INTERCEPTED EARLY AND WAS TRACKING E OF THE DESIRED GND PATH. FO RESELECTED 330 DEG HDG TO CORRECT GND PATH. AT THE SAME TIME APCH ISSUED A TFC ALERT FOR B757 TFC IN FRONT OF US; WITH A SPD ASSIGNMENT AND SLOW DOWN AT 10 NM. WE WERE ALSO STEPPING DOWN TO 7000 FT PER ILS RWY 35L. AS WE INTERCEPTED THE LOC; FLAPS WERE SELECTED TO 10 DEGS; LNDG GEAR WAS SELECTED DOWN. THERE WAS SOME CONFUSION IF WE WERE WITHIN THE SPD CLRNC ISSUED BY APCH. AT THIS TIME THE FLAP OVERSPD WAS NOTICED. THE ACFT WAS SLOWED; FLAPS 25 DEGS AND 30 DEGS WERE SELECTED. A STABILIZED APCH WAS ATTAINED. BEFORE LNDG CHKLIST ACCOMPLISHED. LNDG AND ROLLOUT NORMAL. CAPT WROTE UP THE FLAP OVERSPD. SUPPLEMENTAL INFO FROM ACN 513088: APCH AT DEN AT NIGHT VMC. THE FO WAS THE PF. WE WERE SCHEDULED FOR A 12 HR 13 MIN DUTY DAY. WE EXPECTED DELAYS IN THE DEN TERMINAL AREA DUE TO SEVERE TSTMS WITH HAIL. WE RECEIVED NUMEROUS VECTORS FOR SPACING DURING THE ARR. DUE TO RAPIDLY CHANGING WX CONDITIONS; DEN ATIS WAS BEING UPDATED FREQUENTLY. ATIS CHANGED IN 20-30 MINS. AS PNF; I WAS WORKING WITH THE ACARS TO MAINTAIN CURRENT ATIS SINCE SOME EARLIER RPTS HAD LISTED RVR'S BELOW 1800 FT. WE WERE INTERESTED IN THE MICROBURST AND WINDSHEAR RPTS APPEARING IN THE ATIS. THE COCKPIT WAS BUSY; BUT PERFORMING SMOOTHLY. WE HAD SET UP AND BRIEFED FOR THE RWY 35L ILS. APCH THEN ADVISED OUR RWY WOULD BE RWY 35R. WE UPDATED THE FMC AND RADIOS AND BRIEFED FOR RWY 35R. ON BASE LEG TO INTERCEPT LOC FOR RWY 35R; APCH ADVISED THAT RWY 35L WAS AVAILABLE. FOR BETTER WX AVOIDANCE; WE ACCEPTED AND RESET RADIOS AND FMC FOR RWY 35L. DUE TO WX IN AREA; GAR WOULD BE HARROWING. SINCE WE APPEARED TO BE GAINING ON THE ACFT IN FRONT OF US AND WANTING TO AVOID A GAR DUE TO ACFT ON RWY; WE BEGAN TO SLOW AS FAST AS POSSIBLE. DURING FLAP EXTENSION; I INADVERTENTLY EXTENDED FLAPS TO 15 DEGS WHEN TOO FAST; RESULTING IN OVERSPD. FACTORS CONTRIBUTING: LONG DUTY DAY; LATE NIGHT; WX IN AREA; LOW TIME IN TYPE CREW.