What was found
(CAN) DURING CRUISE THE FLIGHT CREW NOTICED THE NR 1 HYDRAULIC QUANTITY DECREASING. AN UNEENTFUL LANDING WAS COMPLETED. THE MAINTENANCE CREW DISCOVERED THE NR 1 ENGINE DRIVEN PUMP CASE DRAIN LINE HAD CHAFED THROUGH ON A FAIRLEAD CAUSING THE PIPE TO LEAK. THE PIPE WAS REPAIRED AND THE AIRCRAFT RETURNED TO SERVICE.AN INVESTIGATION DETERMINED THE CAUSE OF THE CHAFING WAS DUE TO A SUPPORT CLAMP NOT INSTALLED ON THE PIPE KEEPING IT AWAY FROM THE FAIRLEAD.