Chapter 7—AUXILIARY MACHINERY
HYDRAULIC SYSTEMS
The overall efficiency of the hydraulic installations used to control or drive auxiliary machines is basically dependent upon the size, oil pressure, speed, and stroke of the hydraulic installation. The efficiency of the hydraulic speed gears and the components of the system as a whole will depend upon the care which is given them. Since major repair of hydraulic gear, except for piping and fittings, is generally done in a naval shipyard or by the manufacturers, this section will deal primarily with troubleshooting and preventive maintenance.
Hydraulic transmissions are sturdy, service-proven machines, inspected and tested with such care that casualties seldom occur except as a result of faulty assembly, installation, or maintenance. A correctly installed hydraulic system, operated regularly and serviced with proper care, will retain its design characteristics of power, speed, and control. The need for costly repair and replacement will seldom occur if the equipment has been maintained properly.
TROUBLESHOOTING
Troubleshooting an electrohydraulic system involves the systematic elimination of the possible causes, one by one, until the actual cause of a casualty is found. In attempting to locate the source of any trouble in an electrohydraulic system, remember that all troubles occur in one of three categories—hydraulic, electric, or mechanical. Isolating a trouble into one of these categories is one of the main steps in locating the source of trouble.
Hydraulic Troubles
Casualties in a hydraulic system are generally the result of low oil levels, external or internal leakage, clogged lines or fittings, or improper adjustment of valves and other working parts. Do not disassemble a unit unless you are certain that the trouble exists within that unit. Unnecessary disassembly may create conditions which lead to additional trouble, since dirt may enter an open system.
Leaks are a frequent cause of trouble in hydraulic equipment. Generally, leaks are a result of excessively worn parts, abnormal and continuous vibration, excessively high operating pressures, or faulty or careless assembly. External leaks usually have little effect on the operation of equipment other than a steady draining of the oil supply; but even a small leak wastes oil, and the resulting unsightly appearance of a machine is indicative of poor maintenance procedures.
External leaks may result from any of the following causes: improperly tightened threaded fittings; crossed threads in fittings; improperly fitted or damaged gaskets; distorted or scored sealing rings, oil seals, or packing rings; scored surfaces of working parts; improperly flared tube ends; or flanged joints not seating squarely.
Internal leaks usually result in unsatisfactory operation of the equipment. Large internal leaks are signified by loss of pressure and failure of equipment. While large internal leaks can usually be located by installing pressure gages in various parts of the equipment, the location of small leaks generally requires disassembly and visual inspection of the parts. Internal leaks may result from worn or scored valves, pistons, valve plates or bushings, or improperly fitted or damaged gaskets.
The symptoms of trouble in a hydraulic system are frequently unusual noises. Some noises are characteristic of normal operation and can be disregarded, while others are evidence of serious trouble. Even though the exact sound indicating a specific trouble can be learned only through practical experience, the following descriptive terms will give a general idea of the noises which are trouble warnings.
If POPPING and SPUTTERING noises occur, air is entering the pump intake line. Air entering the system at this point may be the result of too small an intake pipe, an air leak in the suction line, a low oil level in the supply tank, cold or heavy oil, or possibly the use of improper oil.
If air becomes trapped in a hydraulic system, HAMMERING will occur in the equipment or transmission lines. When this occurs, check for improper venting. Sometimes, a POUNDING or RATTLING noise occurs as the result of a partial vacuum produced in the active fluid during high speed operation or when a heavy load is applied. This noise may be unavoidable under the conditions stated and can be ignored if it stops.
when speed or load is reduced. If the noise persists at low speeds or light loads, the system needs to be vented of air. Air in a hydraulic system can also cause uneven motion of the hydraulic motors.
When a GRINDING noise occurs, it can usually be traced to dry bearings, foreign matter in the oil, worn or scored parts, or overtightness of some adjustment.
The term HYDRAULIC CHATTER is sometimes used to identify noises caused by a vibrating spring-actuated valve, by long pipes improperly secured, by air in lines, or by binding of some part of the equipment.
SQUEALS or SQUEAKS indicate that the packing is too tight around some moving part or that a high-frequency vibration is occurring in a relief valve.
Electrical Troubles
Even though troubles occurring in electrical equipment are the responsibility of the Electricianrsquo;s Mate, the Engineman can facilitate maintenance of such equipment by making a few simple checks when electrical troubles occur. Failure to have a switch in the ON position will cause unnecessary delay in operating electrical equipment. If the switch is closed and the equipment still fails to operate, check for blown fuses and tripped circuit breakers. Troubles of this type are usually the result of an overload on the equipment. If a circuit breaker continues to cut out, the trouble may be caused by damaged equipment, excessive binding in the electric motor, obstruction in the hydraulic transmission lines, or faulty operation of the circuit breaker. Check for visual indica
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Chapter 7—AUXILIARY MACHINERY HYDRAULIC SYSTEMS The overall efficiency of the hydraulic installations used to control or drive auxiliary machines is basically dependent upon the size, oil pressure, speed, and stroke of the hydraulic installation. The efficiency of the hydraulic speed gears and the components of the system as a whole will depend upon the care which is given them. Since major repair of hydraulic gear, except for piping and fittings, is generally done in a naval shipyard or by the manufacturers, this section will deal primarily with troubleshooting and preventive maintenance. Hydraulic transmissions are sturdy, service-proven machines, inspected and tested with such care that casualties seldom occur except as a result of faulty assembly, installation, or maintenance. A correctly installed hydraulic system, operated regularly and serviced with proper care, will retain its design characteristics of power, speed, and control. The need for costly repair and replacement will seldom occur if the equipment has been maintained properly. TROUBLESHOOTING Troubleshooting an electrohydraulic system involves the systematic elimination of the possible causes, one by one, until the actual cause of a casualty is found. In attempting to locate the source of any trouble in an electrohydraulic system, remember that all troubles occur in one of three categories—hydraulic, electric, or mechanical. Isolating a trouble into one of these categories is one of the main steps in locating the source of trouble. Hydraulic Troubles Casualties in a hydraulic system are generally the result of low oil levels, external or internal leakage, clogged lines or fittings, or improper adjustment of valves and other working parts. Do not disassemble a unit unless you are certain that the trouble exists within that unit. Unnecessary disassembly may create conditions which lead to additional trouble, since dirt may enter an open system. Leaks are a frequent cause of trouble in hydraulic equipment. Generally, leaks are a result of excessively worn parts, abnormal and continuous vibration, excessively high operating pressures, or faulty or careless assembly. External leaks usually have little effect on the operation of equipment other than a steady draining of the oil supply; but even a small leak wastes oil, and the resulting unsightly appearance of a machine is indicative of poor maintenance procedures. External leaks may result from any of the following causes: improperly tightened threaded fittings; crossed threads in fittings; improperly fitted or damaged gaskets; distorted or scored sealing rings, oil seals, or packing rings; scored surfaces of working parts; improperly flared tube ends; or flanged joints not seating squarely. Internal leaks usually result in unsatisfactory operation of the equipment. Large internal leaks are signified by loss of pressure and failure of equipment. While large internal leaks can usually be located by installing pressure gages in various parts of the equipment, the location of small leaks generally requires disassembly and visual inspection of the parts. Internal leaks may result from worn or scored valves, pistons, valve plates or bushings, or improperly fitted or damaged gaskets. The symptoms of trouble in a hydraulic system are frequently unusual noises. Some noises are characteristic of normal operation and can be disregarded, while others are evidence of serious trouble. Even though the exact sound indicating a specific trouble can be learned only through practical experience, the following descriptive terms will give a general idea of the noises which are trouble warnings. If POPPING and SPUTTERING noises occur, air is entering the pump intake line. Air entering the system at this point may be the result of too small an intake pipe, an air leak in the suction line, a low oil level in the supply tank, cold or heavy oil, or possibly the use of improper oil. If air becomes trapped in a hydraulic system, HAMMERING will occur in the equipment or transmission lines. When this occurs, check for improper venting. Sometimes, a POUNDING or RATTLING noise occurs as the result of a partial vacuum produced in the active fluid during high speed operation or when a heavy load is applied. This noise may be unavoidable under the conditions stated and can be ignored if it stops. when speed or load is reduced. If the noise persists at low speeds or light loads, the system needs to be vented of air. Air in a hydraulic system can also cause uneven motion of the hydraulic motors. When a GRINDING noise occurs, it can usually be traced to dry bearings, foreign matter in the oil, worn or scored parts, or overtightness of some adjustment. The term HYDRAULIC CHATTER is sometimes used to identify noises caused by a vibrating spring-actuated valve, by long pipes improperly secured, by air in lines, or by binding of some part of the equipment. SQUEALS or SQUEAKS indicate that the packing is too tight around some moving part or that a high-frequency vibration is occurring in a relief valve. Electrical Troubles Even though troubles occurring in electrical equipment are the responsibility of the Electricianrsquo;s Mate, the Engineman can facilitate maintenance of such equipment by making a few simple checks when electrical troubles occur. Failure to have a switch in the ON position will cause unnecessary delay in operating electrical equipment. If the switch is closed and the equipment still fails to operate, check for blown fuses and tripped circuit breakers. Troubles of this type are usually the result of an overload on the equipment. If a circuit breaker continues to cut out, the trouble may be caused by damaged equipment, excessive binding in the electric motor, obstruction in the hydraulic transmission lines, or faulty operation of the circuit breaker. Check fo 全文共37312字，剩余内容已隐藏，支付完成后下载完整资料 资料编号：[2384] |
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