If properly installed, the piping and valves of a hydraulic system are seldom a source of trouble, except for leakage. Since some leaks, however, can be of sufficient seriousness to cause a reduction in the efficiency of the unit, frequent inspections should be made for leakage and steps should be taken to eliminate any leakage found. If leaks occur at a flanged joint in the line of a hydraulic system, tighten the flange bolts evenly, but not excessively. If the leaks persist, use the auxiliary gear while the leaking flange is being refitted with copper asbestos or "O" ring packing. Be sure the flange surfaces are cleaned carefully before the packing is applied.

CAUTION: Exposure to asbestos fibers is a recognized health hazard. Refer to N.S.T.M. chapter 635 for safety requirements applicable to handling asbestos packing and gaskets.

Operation of hydraulic equipment may be continued while leakage repairs are being made in some parts of the system if certain measures are taken. When lines in an auxiliary system leak, they should be valved off from the main line con-nection to prevent leakage between the two systems. If leaks occur in the pumping connec-tions to the three-way valves of a steering gear installation, the pump can be cut out with the valve, and another pump cut in. If the three-way valves fail to cut out the leaking unit, and it becomes necessary to cut out both pumps of a steering gear installation, the valves may be closed at the ram cylinder. Since hydraulic systems will work without pressure control, leaking pipes or cylinders of the pressure control can be cut out of the system for repair by closing the valves in the lines where they join the main piping. Expansion lines and replenishment lines in hydraulic systems of older ships are seldom a source of leakage or breakage, since they are not under any appreciable pressure; however, all con-nections must be maintained intact. In more recent installations, however, replenishing lines are under pressure of as much as 300 psi. In these installations, the hydraulic systems should not be operated during repair of the lines.

Relief valves and shuttle valves of a hydraulic system may also be a source of trouble. The seats of relief valves which are leaking should be reground. Loss of power is a symptom of a leak-ing relief valve. Shuttle valves may stick and fail to cut off; this condition is evidenced either by the escape of oil from the high pressure side of the line into the expansion tank or by the failure of the pressure control. When a shuttle valve fails to operate, the stop valves should be closed and the defective valve removed and repaired. Incorrectly adjusted needle valves can be another source of trouble. Needle valves which are adjusted too fine may cause the device operated by the valve to stop short of its intended stopping point. This may happen because the valve adjustment may allow more fluid to pass through leakage points in the system than through the valve.