Ancillary Hydraulic Devices

1. Hydraulic Circuit
Design and Analysis
Ancillary Hydraulic Devices
DR: Samir elshamy
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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 bottom
2) Allows entrained air to escape from oil
3) Prevents localized turbulence in reservoir
4) Promotes heat dissipation through reservoir walls
 The return line should enter the reservoir on the side plate that is opposite
from 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 reservoirs
The 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 escape
2. 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 system
5. 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 type
3)Gas-loaded type which consists of
A.Non-separator type
B.Separator type ,which consists of:
1.Piston type
2.Diaphragm type
3.Bladder type

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Weight –loaded Spring-loaded Gas-loaded

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Applications of accumulators
1) An auxiliary power source
2) A leakage compensator
3) An emergency power source
4) A hydraulic shock absorber

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