ancillary hydraulic devices, dr.samir elshamy

Hydraulic Circuit Design and Analysis

Ancillary Hydraulic Devices

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Ancillary hydraulic devices

Are those important components that don't fall under the major

categories of :

pump ,actuator, conductor

These Ancillary devices are:

reservoir ,accumulator ,heat exchangers ,pressure gages ,flow

meter ,filters and strainers

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Reservoirs

The reservoir serves not only as storage space for the hydraulic fluid used by system but also the principal location where the fluid is conditioned .

The reservoir is where the sludge ,water and metal chips settle and where entered air picked up by the oil is allowed to escape .

The dissipation of heat is also accomplished by properly designed reservoir. A vented breath cap is included and contains air filter screen ,this allows the

tank to breath as the oil level changes due to system demand requirements Baffle plate extends lengthwise across the center of the tank, its height =70%

of the height of the oil level . The purpose of the baffle is to separate the pump inlet line from return line

to prevent the same fluid from recirculating continuously within the tank

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The baffle serves the following functions:1) Permits foreign substances to settle to the bottom2) Allows entrained air to escape from oil3) Prevents localized turbulence in reservoir4) Promotes heat dissipation through reservoir walls

The return line should enter the reservoir on the side plate that is oppositefrom the pump suction line.

To prevent foaming of the oil , the return line should be installed within two pipes diameter from the bottom of the tank.

The pump suction strainer should be below the normal oil level in the reservoir ,if the strainer is located too high ,it will cause a vortex and permit air to enter the suction line.

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Sizing of reservoirsThe sizing of a reservoir is based on the following criteria:1. It must make allowance for dirt and chips to settle and for air to escape2. It must be able to hold all the oil that might drain into the reservoir from

the system .3. It must maintain the oil level high enough to prevent a whirlpool effect at

the pump inlet .4. It should have a surface area large enough to dissipate most of the heat

generated by the system5. It should have adequate air space to allow for thermal expansion of the oil

Volume of the tank = 3 to 5 times of the pump flow rate

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Accumulators it is a device that stores potential energy by means of either gravity , mechanical spring or compressed gases There are three type of accumulators :

1)Weight –loaded , or gravity type 2)Spring-loaded type3)Gas-loaded type which consists of

A.Non-separator typeB.Separator type ,which consists of:

1.Piston type2.Diaphragm type 3.Bladder type

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Weight –loaded Spring-loaded Gas-loaded


Applications of accumulators1) An auxiliary power source2) A leakage compensator3) An emergency power source4) A hydraulic shock absorber

ancillary hydraulic devices, dr.samir elshamy

Engineering