Hydraulic accumulator

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A hydraulic accumulator is a pressure storage reservoir in which a non-compressed hydraulic fluid is held under pressure applied by an external source. External sources can be springs, increased weight, or compressed gas. The accumulator allows the hydraulic system to cope with extreme demand using less powerful pumps, to respond more quickly to temporary requests, and to smooth pulsation. This is a type of energy storage device.

Compressed gas compressors, also called hydro-pneumatic accumulators, are by far the most common type.

Video Hydraulic accumulator

Accumulator type

Tower

The first accumulator for the Armstrong hydraulic dock machine was a simple water tower that was raised. Water is pumped into the tank at the top of this tower by a steam pump. When the dock machine requires hydraulic power, the hydrostatic head from above ground water levels provides the necessary pressure.

This simple tower is very tall. One of the most famous, the Grimsby Dock Tower was opened in 1852, at a height of 300 feet (91 m). The size of these towers makes them expensive to build. This simple tower accumulation was built for less than a decade. Around the same time, John Fowler was working on ferry dock construction near New Holland but could not use the same hydraulic power because poor soil conditions did not allow high accumulator towers to be built. By the time Grimsby opened, it was outdated because Armstrong had developed a more complex accumulator, but was much smaller and weighted for use in New Holland. In 1892, the original Grimsby tower function was replaced, based on Fowler's suggestion, by smaller weighted accumulators at adjacent wharves, although the tower remains today as a famous landmark.

Another surviving tower is bordered by East Float in Birkenhead, England.

Lifting weight

The accumulator gains weight consisting of a fluid-filled vertical cylinder connected to a hydraulic line. The cylinder is closed by a piston in which a series of weights are placed that exert forces downward on the piston and thereby suppress the liquid in the cylinder. In contrast to compressed gas and spring accumulator, this type provides almost constant pressure, regardless of the volume of liquid in the cylinder, until it is empty. (The pressure will decrease slightly as the cylinder is emptied due to the decrease in the remaining liquid weight.)

A working example of this type of accumulator can be found at the home of the hydraulic machine, Bristol Harbor. The original 1887 accumulator was in place on the tower, an external accumulator was added in 1954 and the system was in use until 2010 to power the Cumberland Basin (Bristol) key gate. Water is pumped from the port to the header tank and then fed by gravity to the pump. Working pressure is 750 psi (5.2 MPa, or 52 bar) used to power the Bristol Harbor cranes, bridges and locks.

The original operating mechanism of Tower Bridge, London, also uses this type of accumulator. Although no longer in use, two of the six accumulators can still be seen in the in situ at the bridge museum.

The Regent's Channel Pier, now called Limehouse Basin, has the remains of a hydraulic accumulator, dating from 1869, a part of the world's oldest remaining facility, the second on the dock, slower than Poplar Dock, originally listed incorrectly as cabin signals for London and Blackwall Railway, when correctly identified, it was restored as a tourist attraction by London Docklands Development Corporation which is now dead. Now owned by the British Waterways Board, it is open to large groups on apps to the Dockmaster Office in the basin and on the afternoon of the London Open House Weekend, held on the third weekend of September each year.

London has a vast public hydraulic power system from the mid-nineteenth century that was finally closed in the 1970s with five hydraulic power plants, operated by the London Hydraulic Power Company. Roads and rail ports often have their own systems.

Accumulator contains air

A simple accumulator shape is a closed volume, filled with air. The vertical part of the pipe, often enlarged, may be sufficient and self-filling with air, trapped in filling of the pipe.

Such accumulators do not have sufficient capacity to store electricity for a long time, but they can act as a buffer to absorb pressure fluctuations. They are used to smooth the delivery of the piston pump. Another use is as a shock absorber to reduce water hammer.

Accumulated closed compressed gas (or filled with gas)

A compressed gas accumulator consists of a cylinder with two chambers separated by an elastic diaphragm, an entirely closed bladder, or a floating piston. One room contains a hydraulic fluid and connected to a hydraulic line. The other chamber contains an inert gas under pressure (usually nitrogen) that provides a compressive force in the hydraulic fluid. Inert gas is used because oxygen and oil can form explosive mixtures when combined under high pressure. When the compressed gas volume changes, the gas pressure (and pressure on the fluid) changes in reverse.

It is possible to increase the gas volume of the accumulator by coupling the gas bottle to the accumulator gas side. This is mainly done because the gas bottles are usually cheaper to produce than the accumulators.

The compressed gas accumulator was invented by Jean Mercier for use in variable-pitch propellers.

Spring type

A spring type accumulator is similar in operation to the gas-charged accumulator above, except that a heavy spring (or spring) is used to provide a compressive force. According to Hooke's law, the magnitude of the force given by the spring is directly proportional to the change in length. Therefore, when the spring presses, the force it exerts on the liquid increases linearly.

Metal bellows type

Metal bellows accelerators function similar to compressed gas types, except the elastic diaphragm or floating piston is replaced with an airtight welded metal bellows. The fluid may be internal or external to the bellows. The advantages for this type of metal bellows include very low level springs, allowing the gas charge to perform all work with slight changes in pressure from full to empty, and long strokes relative to the high (empty) density, which gives the maximum storage volume for given container sizes. Welded bellows accelerators provide a very high level of accumulator performance, and can be produced with a broad spectrum spectrum resulting in a wide range of fluid compatibility. Another advantage to this type is that it does not face problems with high pressure operations, thus enabling more energy storage capacity.

Maps Hydraulic accumulator

Works as an accumulator

In modern hydraulic systems, often moving, the preferred item is a gas-loaded accumulator, but a simple system may have springs. There may be more than one accumulator in a system. The exact type and placement of each can be a compromise because of the effect and cost of manufacture.

The accumulator is placed close to the pump with a non-return valve preventing backflow to the pump. In the case of a piston type pump, this accumulator is positioned in an ideal location to absorb the energy pulsation of the multi-piston pump. It also helps protect the system from the fluid hammer. It protects the system components, especially pipework, from both potentially damaging forces.

An additional benefit is the additional energy that can be stored when the pump is subject to low demand. The designer can use smaller capacity pumps. Large excursion of system components, such as landing gear on large planes, requiring considerable fluid volume may also benefit from one or more accumulators. These are often placed close to requests to help overcome restrictions and drag from the long pipe runs. The energy flow from the accumulator usage is much larger, for a short time, than even a large pump can produce.

Accumulators can maintain pressure in the system for periods when there is a slight leak without continuous on-and-off pumps. When temperature changes cause pressure visit, accumulators help absorb it. Its size helps absorb fluids that may be locked in a small fixed system without room for expansion due to valve regulation.

The gas precharge in the accumulator is set so that the separate bladder, diaphragm or piston does not reach or invade both ends of the operating cylinder. The precharge design usually ensures that the moving parts do not contaminate the tip or block the fluid channel. Poor precharge treatment can damage the accumulator operation. Well designed and maintained accumulators should operate without problems for years.

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See also

• Accumulator (energy)

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Note

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References

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External links

• Accumulation and Compatibility Applications
• Online Accumulator Size Calculator
• Hydraulic Accumulator - Detailed discussion of the various types.
• How to Fix Hydraulic Accumulator -
• Online-Calculation of hydraulic accumulator
• Video recording from the hydraulic accumulator tower

Source of the article : Wikipedia