BYPASS DAMPER AT WASTE HEAT WOULD NOT OPEN OR CLOSE. EE WAS ATTEMPTING TO OPEN DAMPER & DISCOVERED ELECTRICAL HOIST CHAIN ""SLACK CHAIN"" WAS STUCK IN THE DAMPER SLOT. EE GRABBED CHAIN & PULLED HARD, AS HE DID HE FELT A SHARP PAIN IN HIS LEFT ARM/SHOULDER. WEATHER CONDITIONS IN THE AREA WERE NOT FAVORABLE AT THE TIME & POWER HOUSE WAS PRODUCING TOO MUCH STEAM, NEEDED TO BYPASS BOILER