Every hydraulic system is built on the same idea. Pressurized fluid succeeds where motors and gears used to finish the work. A pump circulates oil throughout the system. Valves control the flow, and cylinders translate the pressure to linear force. It is efficient, powerful, and precise. However, it lacks reliability. The demand for pressure can overcome the the system, and pumps can be slow to respond. This manufacturer of hydraulic cylinders, power packs, and manifolds, supplies bladder, piston and diaphragm accumulators designed to maintain system reliability for industrial applications. The most useful of his products is the pumped accumulator, which collects the pressure created by the pump during times of low demand, and is then used to supply the system with flow and pressure to a greater extent than the pump can do by itself.
Working Principles of Pumped Accumulator
- Energy Storage of Compressed Gas
The accumulator separates hydraulic fluid from a compressed gas of nitrogen via either a piston, bladder or diaphragm. When the pump forces hydraulic fluid into the accumulator, the gas is compressed and the energy is stored.
- Pre-Charge Pressure
The gas side also contains a pre-charge pressure that sets a pressure baseline for the system when it is off. The pre-charge pressure determines when the accumulator first makes contact with the circuit. If the pre-charge pressure is low, the accumulator will discharge early. If the pre-charge pressure is high, it will have little effect on the circuit. This is a calibration step.
- Charging Phase
In this phase, pre-charge system pressure is exceeded. Fluid is then allowed into the accumulator which in turn pushes the separating element and further compresses the gas. The accumulator accepts this excess output from the pump, which would otherwise be wasted.
- Discharge Phase
This phase begins when pressure in the circuit drops, due to an instantaneous load demand, or a momentary delay from the pump. The gas which has been compressed fully expands, and pushes the fluid which has been stored in the accumulator back into the circuit. The time taken for this process is one of the reasons why accumulators are excellent hydraulic devices for managing pressure.
- Load Support Beyond Pump Capacity
The pump by itself may not have enough capacity to meet the demands of the system in certain situations. In this case, the accumulator is called upon to provide the required flow enabling the system to perform at full flow, while avoiding the installation of a larger pump that is more expensive and consumes more energy.
- Shock Absorption and Pressure Stability
Rapid changes in flow demand, and valve actuation create pressure spikes in a hydraulic system. Over time, these spikes can damage system fittings and seals. The accumulator protects these components by absorbing the pressure spikes. This results in a fully operational hydraulic system.
Implications for a Systems
For plant engineers and designers, there are very few good components in a hydraulic system. Well-designed systems with variable loads and a good level of reliability will use pumped accumulators. When considering the design of a system, wear and failure of seals and hoses will be a design consideration. Teutonic Engineering’s range of accumulators consider these levels of reliability, and have been extensively tested at high discharge rates for consistent functionality in construction and manufacturing, as well as in heavy industrial machinery.
The reliability of a hydraulic system will be determined by its weakest link when the system is under demand. This is specifically the function of a pumped accumulator. Because a pumped accumulator maintains and regulates pressure, and mitigates demand shocks to components, the overall efficiency of the hydraulic system is improved.