We have discussed in our previous post about the
various hydraulic pressure control valves such as...
Pressure relief valve and sequence valve and Difference between pressure reducing valve and pressure relief valve .
Today we will talk about the hydraulic accumulators in
hydraulic unit. We will discuss hydraulic accumulator, types of accumulators,
accumulator which is mostly using these days in industries, principle of
working of accumulator, material of construction of accumulator.
So let us come to the subject without wasting your
time.
Let us recall the conservation of energy, which
states that
“Energy could
neither be created nor be destroyed, but it could be transformed from one form
of energy to other form of energy”
This concept is also used in hydraulic system.
Hydraulic energy, in hydraulic system, will be stored in hydro-static devices
and will release the stored energy when requirement occur.
As we know that practically, fluids are
incompressible and hence in order to provide the characteristics of
compressibility in hydraulic system, we use hydraulic accumulator.
Hydraulic accumulator will store energy by taking a
specified quantity of fluid under pressure and will release the pressure energy
when there will be requirement to perform a task in hydraulic system.
Types of accumulators
There are basically fives types of accumulators used
in industries and these are as mentioned below
- Piston type
- Bladder type
- Diaphragm Type
- Spring type
- Weight loaded
Let us look the above accumulators
Out of above types of accumulators, we mostly see
Bladder type and Diaphragm type of accumulator in modern hydraulic system.
Above mentioned both type of hydraulic accumulators (Bladder type and Diaphragm
type) use characteristics of compressibility of gas for storing the fluid under
pressure.
Bladder type and Diaphragm type of accumulators are quite similar with each other. We can only distinguish Bladder type and Diaphragm type of accumulators on the basis of design of gas tight separating element.
Hydraulic accumulator (Bladder type and Diaphragm
type) will have one section for liquid and one section for gas and these two sections
of accumulator will be separated by a gas tight separating element.
Liquid section will be connected with hydraulic circuit. Accumulator will take the fluid when pressure will be increased and gas will be compressed and when pressure will be reduced, compressed gas will expands to force the stored fluid to hydraulic circuit.
Liquid section will be connected with hydraulic circuit. Accumulator will take the fluid when pressure will be increased and gas will be compressed and when pressure will be reduced, compressed gas will expands to force the stored fluid to hydraulic circuit.
Bladder accumulator will have flexible bladder with
gas valve, pressure vessel and hydraulic connection with non return valve i.e.
check valve.
Pressure vessel will be made by a material having
high tensile strength such as chrome molybdenum steel. Bladder will be made by various grade elastomers
depending upon the operating temperature and medium. Elastomer grade NBR, IIR,
FKM and ECO are mostly used for producing the ideal bladder depending on user
requirement.
- NBR: Acrylonitrile butadiene rubber (Perbunan)
- IIR: Butyl rubber
- FKM: Fluoro rubber (Viton)
- ECO: Ethylene oxide epichlorohydrin rubber
In order to avoid from corrosion, accumulator shell
will be chemically nickel plated from inside.
Symbol used for indicating the accumulator in hydraulic circuit
Accumulator in hydraulic circuit
We will discuss few more important points such as
need and applications of hydraulic accumulators in our next post.
Also discuss
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