Hydraulic systems maintenance

Most hydraulic systems have built-in sources of air. Leaky seals in gas-pressurized accumulators and reservoirs can feed gas into a system faster than it can be removed, even with the best of maintenance. Another lesser-known but major source of air is air that is sucked into the system past actuator piston rod seals. This occurs when the piston rod that is stroked by some external means while the actuator itself is not pressurized. 

Maintaining hydraulic fluid within allowable contamination limits for both water and particulate matter is cmcial to the care and protection of hydraulic equipment. Filters will provide adequate control of the particular contamination problem during all normal hydraulic system operations if the filtration system is installed properly and filter maintenance is performed properly. Filter maintenance includes changing elements at proper intervals. 

Mineral Oil Hydraulic Fluids. Populations with potentially high exposures to mineral oil hydraulic fluids include all occupations that maintain hydraulic equipment including automobile, truck, and tractor mechanics, mechanics employed by heavy industry and mining operations to repair and maintain hydraulic equipment, and other maintenance workers involved with the repair and maintenance of hydraulic systems. The number of workers with potentially high exposures to mineral oil hydraulic fluids is expected to be very large. 

One of the major advantages of these fluids is that they are all compatible with each other in all proportions and with all the aircraft hydraulic systems and hydraulic system materials designed to use any of these three hydraulic fluids. That has enabled transition from one to the other by attrition, i.e. just convert by topping off with the new hydraulic fluid. This saves considerable fluid and maintenance time compared to repeatedly flushing and filling to obtain a high percentage of the new fluid in the aircraft. 

Hydraulic System. Generally, for vertical pan dryers an hydraulic system is provided for the agitator rotation, the opening-closing of the dryer by a rapid device as bayonet and/or TRI-CLAMP and the lowering of the vessel for maintenance or cleaning purposes. The hydraulic components positioned on the dryer are normally ... 

The hydraulic system consists of oil reservoir, electric motor, hydraulic pump, heat exchange for oil cooling, oil filters, oil level indicator, electric valves and flow distributors. An hydraulic plant which has been properly installed and care has been taken during the start-up phase, should enjoy long life and not need much maintenance. 

Based on manufacturers recommendations and experience, laboratories perform regular preventative maintenance procedures on the analyzers, with some additional maintenance procedures initiated in response to internal quality control performance or analyzer malfunctions. Calibration and quality control performances should always be checked after maintenance visits because replacement parts and disturbances of the optical and hydraulic systems sometimes adversely affect subsequent analyzer performance (sometimes called PMT—postmaintenance visit trauma). These procedures form part of good laboratory practice. 

Compared to hydraulic drives, electric drives have the advantage of lower energy consumption and lower noise levels. They also require less maintenance, as they operate without a centralized hydraulic system. On the... 

The reactor system does not have any feedback control system at all. The plant is started up by heat from the primary pump which raises the system temperature to 350 C. Then, the reflector is lifted by the hydraulic system to reach the critical state at 350°C. The system temperature is raised up to 430 C by nuclear fission heating and maintenance thre by moving the reflector upwards. 

Maintenance of the Integrity of the water barrier will probably call for more control and maintenance of auxiliary systems than otherwise. The techniques for limiting the sources of water in the process area may include, in addition to cmtrols on routinely added moderator, controls on coolant and hydraulic systems and on firefighting. 

The use of water of reactor quality as the operating fluid eliminates the need for special hydraulic systems, with their inherent leakage and maintenance problems. 

Hydraulic-Lift Trucks. Flydrauhc-Uft trucks (Fig. 4.41) are used for short distance moves at the workplace. They generally range in capacity from 2500 to 8000 lb (1130 to 3625 kg). These trucks require a minimum amount of maintenance, and can last for 20 years. The trucks can be equipped with a jacklike manually operated hydraulic lift or pedal operated system to elevate a loaded pallet. Some units use an electrically driven hydraulic system to lift, often above the maximum 5 in of the manual system. These lift trucks generally use forks for lifting pallets or platforms for special containers and positioning heavy loads. 

Portable Hand-Powered Crane. The portable hand-powered crane is similar in design to a small manual-lift truck, except that the load-carrying forks have been replaced by a boom and hook. This equipment is commonly used to move and position work pieces into and out of process equipment where volumes do not warrant a permanently installed hoisting system. It is also frequently found in maintenance and repair shops to assist in the disassembly and reassembly of in-plant equipment. Lifting is accomplished either through a hand winch and cable system or a manually operated hydraulic system. Typical lifting capacities are limited to 2000 lb (900 kg) or less. 

In order to maintain your hydraulic systems, you must have preventive maintenance procedures and you must have a good understanding and knowledge of Best Maintenance Practices for hydraulic systems. We will convey these practices to you. See Table 15.1. 

Preventive maintenance (PM) of a hydraulic system is very basic and simple and if followed properly can eliminate most hydraulic component failure. Preventive maintenance is a discipline and must be followed as such in order to obtain results. We must view PM programs as performance oriented and not activity oriented. Many organizations have good PM procedures but do not require maintenance personnel to follow them or hold personnel accountable for the proper execution of these procedures. In order to develop a preventive maintenance program for your system you must follow these steps ... 

Second What requirements does the equipment manufacturer state for preventive maintenance on the hydraulic system ... 

A list of preventive maintenance tasks for a hydraulic system could be ... 

Preventive maintenance is the core support that a hydraulic system must have in order to maximi2e component life and reduce system failure. Preventive maintenance procedures that are properly written and followed properly will allow equipment to operate to its fuU potential and life cycle. Preventive maintenance allows a maintenance department to control a hydraulic system rather than the system controlling the maintenance department. We must control a hydraulic system by telling it when we will perform maintenance on it and how much money we will spend on the maintenance for the system. Most companies allow hydraulic systems to control the maintenance on them at a much higher cost. 

In order to measure success of a hydraulic maintenance program we must have a way of tracking success but first we need to establish a benchmark. A benchmark is method by which we will establish certain key measurement tools that will tell you the current status of your hydraulic system and then tell you if you are succeeding in your maintenance program. 

Modifications to an existing hydraulic system need to be accomplished professionally. A modification to a hydraulic system in order to improve the maintenance efficiency is important to a company s goal of maximum equipment reliability and reduced maintenance cost. 

To summarize, maintenance of a hydraulic system is the first line of defense to prevent component failure and thus improve equipment reliability. As discussed earlier, discipline is the key to the success of any proactive maintenance program. 

The application of maintenance decision diagram for hydraulic systems components is shown in Table 6 taking as an example of application the analysis of the Electric Motor A.C. 

Control of the size and amount of contamination entering the system from any other source is the responsibility of the personnel who service and maintain the equipment. During installation, maintenance, and repair of hydraulic equipment, the retention of cleanliness of the system is of paramount importance for subsequent satisfactory performance. 

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