Hydraulic systems installation

Most hydraulic systems use a positive displacement pump to generate energy within the system. Unless the pressure is controlled, these pumps will generate excessive pressure that can cause catastrophic failure of system component. A relief valve is always installed downstream of the hydraulic pump to prevent excessive pressure and to provide a positive relief should a problem develop within the system. The relief valve is designed to open at a preset system pressure. When the valve opens, it diverts flow to the receiver tank or reservoir. 

To minimize the loss of useable energy lost to its conversion to heat energy, care must be taken in the design, installation and operation of hydraulic system. As a minimum the following factors must be considered ... 

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. 

The most common device installed in hydraulic systems to prevent foreign particles and contaminations from remaining in the system are referred to as hlters. They may be located in the reservoir, in the return line, in the pressure line, or in any other location in the system where the designer of the system decides they are needed to safeguard the system against impurities. 

Clean hydraulic fluid is essential for proper operation and acceptable component life in all hydraulic systems. While every effort must be made to prevent contaminants from entering the system, contaminants that do find their way into the system must be removed. Filtration devices are installed at key points in fluid power systems to remove the contaminants that enter the system along with those that are generated during normal operations of the system. 

Main system relief valves are generally installed between the pump or pressure source and the first system isolation valve. The valve must be large enough to allow the full output of the hydraulic pump to be delivered back to the reservoir. This design feature, called a full-flow bypass, is essential for all hydraulic systems. The location... 

The decision to retrofit or install new filters is influenced by plant-specific factors such as the condition of the existing filters, compatibility of the filters to retrofit, availability of space within the plant, etc. Bayer s analysis of the costs and benefits of the retrofit compared to the investment in new filters did not show a clear favourite either decision could be justified. With regard to the rubber lining, gaskets, hydraulic system etc., the Kellys were in very good condition. Because of this, the decision was made to retrofit two of the filters and to use them in a separate brine circuit for the new electrolysers, with a second circuit feeding the amalgam plant. 

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. 

The reflector is moved upward by the hydraulic pump during start up. During power operation, the reflector is held by the hydraulic system and gradually moves up for bum-up compensation at a constant speed of Imm/day without any speed control system. To attain this very slow speed, a reduction mechanism composed of paradox planetary gears is installed. The technical reliability of the gears has been demonstrated elsewhere. However, a spare set of gears is installed in the 4S in case of trouble. To shut down the reflector, the scram valve is opened in the hydraulic circuit. When the reflector lowers Im, the core reaches the subcritical cold shutdown state. The length of the downward movement of the reflector is determined by the capacity of the hydraulic cylinder. It cannot move otherwise. 

Although the author enumerates some application details of rubber seals, the primary focus of this book is on the characteristics of rubbers as seals. Their manufacturing procedures, the implications of their physical and chemical characteristics for sealing in fluid and hydraulic systems, how rubbers seal and prevent leaks, what properties are required for sealing function, and how they change before and after installation are also discussed. It is hoped fliat this will draw mechanical engineers closer to rubber technology. 

In hydraulic systems, where more than one O ring is used in an application, the following installation requirements should be complied with ... 

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. 

Never touch a hydraulic filter with your hand during installation. By touching the filter you will introduce contamination to the hydraulic system. 

Pipe systems installed in a water environment require design consideration for external hydraulic pressure, submergence weighting, and floatation. Any river, lake or stream crossing is considered a water environment. Wetlands and marshes are also considered water environments. 

Seal systems can be used to enhance the usefulness of the DP cell by facilitating pressure measurement for many temperature ranges (—73°C to427°C) [4]. They serve to protect the transmitter from the process fluid, using a hydraulic system to conduct the pressure from the process fluid to the transmitter. Only the seal s diaphragm contacts the process fluid and a capillary or tube of fluid transfers the process pressure from the diaphragm to the transmitter. Before a seal is installed, consider ambient condihons, such as temperature, which may introduce errors. 

Janoff, Vicic, and Cain [11] used accelerated life test methods to select the best material to use for lip seals used in water/glycol fluids contained in subsea oil-field hydraulic systems. The required seal life was 20 years at 93°C sustained temperature at 20.7 MPa pressure with 100 mechanical operations. Finite Element Analysis was used to determine the actual seal temperature in the installed component to establish the service temperature rating. Polyurethane and thermoplastic alloy seals were tested in water/glycol and hydrocarbon hydraulic fluids at 3—5 elevated temperatures at 20.7 MPa constant pressure. Failure was defined as seal leakage at pressure. Test results were analyzed using Least Squares regression in an equation like that used by KenneUey et al. The correlation coefficients exceeded 0.95 and show excellent fit to the model. Table 16B.1 shows the results of the study. 

Table 3 provides recommended start-up and shut-down procedures. Effort should be made to avoid subjecting units to thermal shock, overpressure, and/or hydraulic hammer, since these conditions may impose stresses, that exceed the mechanical strength of the unit or the system in which it is installed, which may result in leaks and/or other damage to the unit or entire system. 

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. 

Case Study. Such a situation was found to occur in the duct network shown in Fig. 21 and installed to extract iron oxide dust at various points along a cold strip processing line. The stated problems were insufficient suction at the hoods, buildup of contaminant in the hoods and along the processing line (causing cleanup problems due to eventual mixing with hydraulic fluid, lubricant, water, etc.). Analysis of the system found the following ... 

The speed of the pig is controlled by regulating the discharge pressure of the hydraulic fluid pressure line. This can be determined and monitored by installing a pressure gauge on the system. 

The reaetive filters suffer from hydraulic blockage due to ealeite crystal staining of the filter granules. Additional equipment (compressors for pressurized air with which the filters ean be periodieally baek-flushed) had to be installed. Not only does this lead to higher eosts due to depreciation of the equipment and more manpower, but also is ineonsistent with the overall coneept of a passive, maintenanee-ffee system. 

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