Hydraulic System Assembly

Hydraulic System Installation Requirements

During the assembly and installation of hydraulic systems, the first concern is to provide easy access to the components and assemblies.  The service replacement of a system component should not require disassembling of neighboring components and hydraulic drive components.  Hydraulic systems should also not bear the weight of connecting pipes.  Additionally, loads caused by elastic deformation are undesirable and lead to future maintenance problems and should be avoided.

Sufficient pressure of hydraulic fluid should be provided in the hydraulic suction line.  The diameter of the suction line should not be less than the mean diameter of the pump’s suction inlet pipe.  The flow rate of the fluid in the suction line should also be limited to approximately 1.2 meters per second.  The resistance should be minimal with pressure in a range of between 0.02 – 0.025 MPa.  The rate of fluid flow in the drain lines of hydraulic drives with open circulation, should not exceed the flow rate in the suction line.  Otherwise, air and oil emulsion will form in the hydraulic tank when being drained.  The drain outlet should be submerged in the oil at a 45 degree angle.  The minimum clearance of the outlet from the bottom of the tank is calculated as twice the diameter of the drain pipe.

To prevent formation of air pockets, the drain outlets of hydraulic machines should be oriented in an upward direction.  If the drain line is long, its cross section should be increased to prevent pressure build up in the machine.

Connections are made by either flexible steel lines or rubber-metal hoses.  The specifications of the lines or hoses should meet the following requirements:

  • the hoses must not hang or kink;
  • sharp bends or twists are not allowed;
  • the hoses must not rub against each other and other components of the machine during operation;
  • the length of a straight part near the connection must be at least six times the external diameter of the hose.

Air removal devices are installed in the topmost point of the pipes.

Assembly and Installation of Hydraulic Machines and Hydraulic Systems

Assembly is begun by testing all components and parts ensuring that all required parts are present and on hand.  The first parts to be assembled are hydraulic assemblies, connection lines and instrumentation.  Control and cooling systems are next in the assembly process.  During assembly, all openings for the entry and exit of hydraulic fluids must be tightly sealed with plugs.  Purification and etching of internal surfaces of the pipes is mandatory.  Following the purification and etching process, the pipes are rinsed in special baths, dried with hot air and plugged until installation.  To ensure pipe integrity and performance at high pressure, they are tested before installation using twice the normal operating pressure.

The correct installation of sealing materials requires additional attention.  Dents, chips and other damage on the surface of parts for connecting and sealing is unacceptable and will lead to fluids leaks.  The size and cleanliness of contacting surfaces must comply with the existing standards and regulations.

Before installing the seals, a lint-free swab, soaked in benzene, is used to treat the seal surfaces and the surfaces they will make contact with.  Next, the surfaces are dried at room temperature until the benzene evaporates.  Only then can the seals and part surfaces be coated with the operating liquid or a lubricating material neutral to the material of the seal.

Seals must not be warped, stretched, twisted or damaged in any way.  If the sealed components do not have bevels, special assembly arbors are used for installation of seals with uneven or step-shaped parts.

Assembly and dis-assembly of positive displacement hydraulic drives must be done in accordance with the operators manual.

Filling of the System with Hydraulic Fluid

Upon completion of assembly, hydraulic fluid will be placed into the equipment.  Special attention must  be paid as to the correct type and correct amount of hydraulic fluid that will be put into the system.  The fluid must not contain water and solid particles must be removed by special filtration equipment prior to filling.

GlobeCore offers the UVR line of equipment for this purpose and it is based on unique and industry leading technology.  The GlobeCore UVR system is equipped with drying and degassing sections. Solved gases and water are removed from the oil by vacuum and the liquid is filtered.  The remaining contaminants are removed by Fuller’s Earth adsorbents.

The advantage of GlobeCore’s equipment is its versatility.  The UVR systems not only process hydraulic oils, they also process transformer oil, turbine oil, industrial oils, diesel fuel, HFO, kerosene, gas condensate and gasoline.

After using the GlobeCore Process of oil purification, the hydraulic oil is fully restored and is made to comply with and/or exceed industry standards.  After using the GlobeCore Process, your company can confidently avoid the cost of repairs and replacement of components that would have most likely failed due contaminated hydraulic fluid.

Filtration fineness cannot  exceed that of the finest filter in the hydraulic system.  Hydraulic fluid is filled into the system at special filling stations equipped with manual or mechanical drives.  The use of such stations have several obvious advantages.  (1) Availability of a tank protecting the oil from contamination during transportation, storage and filling;  and (2)  input and output fine filters providing the required fineness of filtration.

Filling of a positive displacement hydraulic system can be roughly divided into three stages: (1) The first stage is to fill the oil into the hydraulic system and remove air through the drain system.  The fluid is fed through the assembly line and into the lower drain point of the hydraulic drive.  As liquid enters the system, air is pushed out into the hydraulic tank through the top drain point;  (2) The hydraulic tank is filled to the top level; and (3) the hydraulic system is then topped off with fluid.

After completion of the these three stages, the positive displacement hydraulic drive is tested at idle with minimal rotation speed of the drive shaft.  The tests are repeated every 15 seconds. Hydraulic system filling is controlled by the rate of decrease in the hydraulic tank fluid level.  When the tank is filled, the drive motor is starts to operate at idle speed.  It operates at this speed for 3 to 5 minutes.  The system is then filled with liquid to the required level usually indicated by the mark on the hydraulic tank indicator.


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