1. Introduction 1.1 History of hydraulic accumulator 2. Types of hydraulic accumulator 2.1 Tower type accumulator 2.2 Raised weight accumulator 2.3 Spring-type accumulator 2.4 Compressed-gas accumulator a) Bladder type accumulator b) Diaphragm type c) Piston type accumulator d) Metal bellow type 3. Hydraulic symbols 4. Functions. 5. Design consideration 5.1 calculations 5.2 calculation of useful volume 6. Applications 6.1 Injection molding machine hydraulic circuit 6.2 Leakage Oil Compensation hydraulic circuit 6.3 Shortening of Stroke Time hydraulic circuit 7. Conclusion

1. Chandan Nagaraja
1RV08ME021
R.V.College of Engineering,
Bengaluru

2. OVERVIEW
 Introduction
 History
 Types of Hydraulic Accumulator
 Functions of Accumulator
 Accumulator design consideration
 Application
 Conclusion

3. INTRODUCTION
 A Hydraulic Accumulator is energy storage device.
 It is pressure storage reservoir in which a non-
compressible hydraulic fluid is held under pressure by an
external source.
 The external source used can be a spring, a raised
weight, or a compressed gas.
 The main reasons that an accumulator is used in a
hydraulic system, is that the pump doesn’t need to be so
large to cope with extremes of demand and supply circuit
can respond quickly to any temporary demand and to
smooth pulsation.

4. HISTORY
 First Hydraulic accumulator was made
by William Armstrong in 1846 built a
crane powered by water of town mains
at Newcastle, United Kingdom.
 Later 1852 ,Armstrong used Grimsby
Dock Tower for the constant pressure
for cranes, lock gates and sluices.
 Grimsby Dock Tower is hydraulic
accumulator is used for the purpose of
containing a 30,000UK gallon (136 m3)
hydraulic wrought iron reservoir at a
height of 300feet (91 m) to provide
power for lock gates and cranes of
Grimsby Dock.

5. TYPES OF HYDRAULIC
ACCULUMATOR
1. Tower type accumulator
2. Raised weight accumulator
3. Compressed-gas accumulator
a) Bladder type accumulator
b) Diaphragm type accumulator
c) Piston type accumulator
d) Metal bellow type accumulator
4. Spring accumulator

6. 1. TOWER TYPE ACCUMULATOR
 The first accumulators for
Armstrong’s hydraulic dock
machinery were simple raised water
tower.
 It uses hydraulic head
 It delivers constant pressure to the
output
LONDON TOWER BRIDGE

7. 2. RAISED WEIGHT ACCUMULATOR
 A raised weight accumulator consists
of a vertical cylinder containing fluid
to the hydraulic line.
 The cylinder is closed by a piston on
which a series of weights are placed
that exert a downward force on the
piston and thereby energizes the fluid
in the cylinder.
 Gravity acts on the weight to
pressurize the hydraulic system fluid,
thus storing energy.

8. ADVANTGES :
 Used to meet heavy industrial
requirements.
 Extremely high capacity at low cost.
 Rugged and durable construction.
LIMITATIONS :
 Extremely bulky and heavy.
 Problem in sealing.
 In contrast to compressed gas
Hydraulic engine
accumulator, this type delivers a nearly
house, Bristol Harbor.
constant pressure, regardless of the volume
of fluid in the cylinder, until it is empty

9. 3. COMPRESSED GAS ACCUMULATOR
 It is widely used accumulator in present scenario.
 It is popularly known as “hydro-pneumatic
accumulator”. It apply force to the liquid by using a
compressed gas that acts as the spring.
 It uses inert gas (nitrogen) under pressure that provides
the compressive force on fluid.
 Oxygen is not used because oxygen and oil can form an
explosive mixture when combined under pressure
 As the volume of the compressed gas changes the
pressure of the gas, and pressure of the fluid, changes
inversely.

10. a) BLADDER TYPE ACCUMULATOR
 A bladder accumulator consists of seamless high-
pressure cylinder with an internal elastomeric bladder
with pressurized nitrogen on it and hydraulic fluid on
the other(external) side.
 The accumulator is charged with nitrogen through a
valve installed on the top. The accumulator will be
pre-charged to nominal pressure when the pumps are
not operating.
 The maximum flow rate of the accumulator is controlled
by the opening orifice and the pressure difference across
the opening.
 Bladder material widely used are epichlorohydric
rubber(ECO) and Acrylonitrile butadiene rubber (NBR).

11. Bladder Accumulator
(Various stages of operation)

12. ADVANTAGES :
 Fast acting
 Not susceptible to contamination
 Consists behavior under similar condition
LIMITATIONS :
 Compressed ratio is
limited, approximately 4:1
 Bladder failure.

13. b) DIAPHRAGM TYPE ACCUMULATOR
 A similar to bladder type, expect an elastomeric
diaphragm is used in place of a bag.
 This would typically reduce the usable volume of the
accumulator, so the diaphragm accumulator may not
have volume capacity of a bladder accumulator.
 Diaphragm accumulator may be spherical or cylindrical.
 The main difference with bladder accumulator is an
increased maximum compression ratio of approximately
8:1
 It is low weight, compact design and good for shock
applications (good response characteristics)

14. DIAPHRAGM TYPE ACCUMULATOR

15. DIAPHRAGM TYPE ACCUMULATOR

16. c) PISTON TYPE ACCUMULATOR
 This accumulator consists of a cylinder assembly, a
piston assembly, and two end-cap assemblies.
 An accumulator contains a free-floating piston with
liquid on one side of the piston and pre-charged air or
nitrogen on the other side.
 An increase of liquid volume decreases the gas volume
and increases gas pressure, which provides a work
potential when the liquid is allowed to dis-charged.

17. PISTON TYPE ACCUMULATOR
ADVANTAGES :
 High compression ratio up to 10:1
 Higher flow rate than bladder type.
LIMITATIONS :
 They are more susceptible to fluid contamination
 Lower response time than the bladder and diaphragm

18. d) METAL BELLOW ACCUMULATOR
 The metal bellows accumulator is
similar to bladder type, expect the
elastic is replaced by a hermitically
sealed welded metal bellows.
 Fluid may be internal or external to
the bellows.
Internal
 It is used when a fast response time is
not critical, yet reliability is important.
 Metal bellow types are pre-charged by
supplier and then permanently sealed
leading to a maintenance free
accumulator.

19. METAL BELLOW ACCUMULATOR
ADVANTGES :
 Metal bellow type include exceptionally low
spring rate, allowing the gas charge to do all the
work with little change in pressure from full to
empty, and long stroke relative solid
height, which gives maximum storage volume
for a given container size.
 It provides exceptionally high level accumulator
performance.
 It can be produced with broad spectrum of
alloys resulting broad range of fluid
compatibility.
LIMITATIONS :
 Response time is more
 High cost External
External

20. 4. Spring type accumulator
 It uses the energy stored in springs to create a constant force
on the liquid contained in an adjacent ram assembly.
 The load characteristics of a spring are such that the energy
storage depends on the force required to compress s spring.
 The free (uncompressed) length of a spring represents zero
energy storage.
 As a spring is compressed to the maximum installed
length, high pressure value of the liquid in a ram assembly is
established.
 As liquid under pressure enters the ram cylinder, causing a
spring to compress, the pressure on the liquid will rise
because of the increased loading required to compress the
spring.

21. Spring loaded accumulator
 It acts according to Hook’s law, magnitude of the force
exerted by the spring is linearly proportional to its
extension.

22. HYDARULIC SYMBOLS

23. HYDARULIC SYMBOLS

24. FUNCTIONS : Where are accumulators used?
Accumulators can be applied creatively in any number of situations, including:
 Emergency and safety: An accumulator which is kept constantly under
pressure is valuable in the event of an electrical power failure as it can provide
flow and pressure to perform an additional function or complete a machine
cycle.
 Shock or pulsation dampening: An accumulator can be used to cushion the
pressure spike from sudden valve closure, the pulsation from pumps or the load
reaction from sudden movement of parts connected to hydraulic cylinders.
 Leakage compensation: An accumulator can be used to maintain pressure
and make-up for lost fluid due to internal leakage of system components
including cylinders and valves.
 Thermal expansion: An accumulator can absorb the pressure differences
caused by temperature variations in a closed hydraulic system.
 Noise reduction: An accumulator is effective at reducing hydraulic system
noise caused by relief valves, pump pulsations, system shock and other circuit
generated noises.

25.  Energy conservation: An accumulator can be used to supplement a pump
during peak demand thereby reducing the size of the pump and motor
required. The accumulator is charged during low demand portions of the pump
cycle time and then discharges during the high demand portions of the system.
 Improved response times: An accumulator (bladder type) has virtually
instantaneous response time that can provide fluid very quickly to fast-acting
valves such as servos and proportional to improve their effectiveness
Accumulator
Adapter Discharge,
fitting, Flange manual
Pressure-
Hydraulic Discharge valve, electric
relief
Symbol (optional)
valve
Manifold Block Gauge
P-port port
Shut-off valve

26. ACCUMULATOR DESIGN CONSIDERATION :
(What must I know to size and select an accumulator?)
 Accumulator type
 Accumulator volume
 Nominal hydraulic system pressure
 Minimum and Maximum hydraulic system pressure
 Pre-charge pressure
 Required flow rate
 Output volume capacity
 Recharge time
 Response time
 Fluid type

27. CALACULATIONS
Pressures :
For the calculation of an accumulator, the following pressures are of decisive significance:
p0 = gas charge pressure at room temperature
and drained fluid chamber
p0 (t ) = gas charge pressure at operating temperature
p0 (tmax) = gas charge pressure at max. operating temperature
p1 = minimum operating pressure
p2 = maximum operating pressure
pm = medium operating pressure
V0 = nominal capacity of the accumulator
To achieve the best possible utilization of the accumulator capacity and a long service life, it is
recommended that the following values be adhered to:
p0 (tmax) ≈0.9* p1 (1)
The highest hydraulic pressure should not exceed the quadruple of the pre-charge pressure;
otherwise, the elasticity of the bladder is overstressed and excessive variations in the compression
result in strong heating up of the gas:
p2 ≤ 4 * p0 (2)

28. Cont………
a) In the case of isothermal changes of state of gases, that is, when the gas buffer changes
so slowly that enough time is available for a complete heat exchange between the nitrogen and its
surroundings and the temperature therefore remains constant, the following is valid:
p0 • V0 = p1 • V1 = p2 • V2 (3.1)
b) In the case of an adiabatic change of state, that is, with a rapid change of the gas buffer, in
which the temperature of the nitrogen changes as well, the following is valid:
p0 • V0^γ = p1 • V1^γ = p2 • V2^γ
(3.2)
γ = ratio of the specific heat of gases (adiabatic exponent) for nitrogen = 1.4
In practice, changes in state rather follow adiabatic laws. Charging is often isothermal, discharging
adiabatic.
Oil volume : Pressures p0 … p2 determine gas volumes V0 … V2. Here, V0 is also the nominal
capacity of the accumulator. The available oil volume V corresponds to the difference between gas
volumes V1 and V2:
dV ≤ V1 – V2 (4)

30. 

31. Hydraulic –accumulator circuit
Accumulator
Cylinder assembly
4/3 directional
valve with solenoid
actuation
PRV
Check measuring
valve jar
power unit Hydraulic Pump

32. Electrical circuit

33. APPLICATIONS
Accumulators are devices used to store fluid power to do the following:
 Dampen pulsations and shocks of a periodic nature
 Increase the speed of the operational circuit.
 Clamping devices to hold the jaw vices and fixtures
 Standby power supply circuits.
 Surge reduction circuits
 Agricultural Machinery & Equipment
 Forestry Equipment
 Oil Field & Offshore
 Machine Tools and Off- Road Equipment
 Mining Machinery & Equipment
 Mobile & Construction Equipment
 Suspension in vehicles

34. Energy Storage in an Injection Molding Machine
Accumulator
safety block
Hydro electric
for
Pressure Switch
diaphragm-
type

36. Leakage Oil Compensation circuit & Shortening Time circuit
of Stroke Time

37. CONCLUSION
So what are the benefits of using accumulators?
 Lower installed system costs, accumulator assisted
hydraulics can reduce the size of the pump and electric
motor which results in a smaller amount of oil used, a
smaller reservoir and reduced equipment costs.
 Less leakage and maintenance costs, the ability to reduce
system shocks will prolong component life, reduce leakage
from pipe joints and minimize hydraulic system
maintenance costs.
 Improved performance, low inertia bladder accumulators
can provide instantaneous response time to meet peak flow
requirements. They can also help to achieve constant
pressure in systems using variable displacement pumps for
improved productivity and quality.

38.  Reduced noise levels, reduced pump and motor size
couple with system shock absorption overall machine
sound levels and results in higher operator
productivity.
 Flexible design approaches. A wide range of
accumulator types and sizes, including accessory
items, provides a versatile and easy to apply design
approach.
 Reduced energy costs, cost savings of up to 33% are
achievable in high performance industrial machinery
using accumulators.