Understanding Accumulators in Hydraulic Systems
Accumulators serve critical functions in many hydraulic circuits, coming in various forms to store or absorb hydraulic energy. When used for energy storage, they receive pressurized hydraulic fluid, which can be released later to aid pump flow or act independently for emergency power. Accumulators can also hold pressure after the pump stops by compensating for leakage.
Automotive Lift Repair Orlando Accumulators are also used to absorb energy in different scenarios. For example, if the flow returning from a large-bore cylinder exceeds the capacity of the plumbing, a low-pressure accumulator can store the excess fluid and release it at a manageable rate. Furthermore, accumulators help address the thermal expansion of hydraulic fluid, which can create dangerously high or low pressure due to temperature changes. By absorbing or supplying the expanding or contracting fluid, accumulators protect the system and reduce noise and vibration from pressure pulses.
Safety Tip
Automotive Lift Repair Orlando Accumulators store energy, and working with them requires caution. Before performing maintenance on an accumulator or connected components, all stored energy must be safely released or isolated, including any residual gas pressure.
Automotive Lift Repair Orlando Accumulators are typically preloaded to ensure a minimum pressure of available fluid. Preloading can be done using weights, springs, or gas. Of these, only weighted accumulators maintain constant pressure, but they are generally impractical for mobile applications due to their size and weight. Spring-loaded and gas-charged accumulators are more compact and can be mounted either vertically or horizontally, though vertical mounting is preferred.
Gas accumulators, sometimes called gas springs, come in several types, including piston, noise suppressor, bellows, diaphragm, bladder, and air-over-oil designs. These accumulators compress gas, usually nitrogen, to store hydraulic fluid. Safety considerations are paramount, as compressed gas can heat up, creating risks of ignition if air (which contains oxygen) is used instead of nitrogen.
Regular monitoring of these pressures helps ensure proper function. If the precharge pressure decreases too frequently, it may indicate a failure in the accumulator’s barrier, requiring repair or replacement.
– Bladder Accumulators: These use an expandable bladder within a metal bottle to store pressurized gas. A charging valve fills the bladder, and a poppet valve prevents damage during precharge.
– Diaphragm Accumulators: A rubber disc isolates gas from fluid in these accumulators, which use spherical shells and are sometimes not serviceable.
– Bellows Accumulators: Less common, these use expandable metal chambers precharged with nitrogen. They are ideal for harsh environments due to their durable, friction-free design.
– Noise Suppressors: Accumulators used to reduce noise and vibration in hydraulic systems by absorbing energy pulses from hydraulic pumps.
– Air-over-oil Systems: A simpler type of accumulator that uses air pressure to store hydraulic fluid. However, this design has limitations, including increased risk of fluid ignition and mixing of air with fluid, which can affect performance.
Each of these accumulator types serves specific functions in hydraulic circuits, contributing to energy storage, noise reduction, and system stability.
Hydraulic Accumulators: An Underutilized Resource
Automotive Lift Repair Orlando Hydraulic accumulators are often overlooked tools in fluid power systems, despite offering numerous benefits. They are frequently misunderstood, particularly in troubleshooting scenarios, but their operational principles are relatively simple, even if the calculations for their specifications can be challenging.
Accumulators fall into two main categories: mechanical and hydropneumatic. Mechanical accumulators can be loaded with either a spring or a mass, but their use is rare. Automotive Lift Repair Orlando Spring-loaded accumulators are typically piston types, where the spring opposes the hydraulic fluid. The compression of the spring affects the output level; as the piston moves toward the outlet, potential energy is lost.
Weight-loaded accumulators, also piston types, rely on gravity to pressurize the fluid. They are mounted vertically and can maintain consistent pressure throughout the piston’s stroke due to the constant force of gravity. However, since mechanical accumulators are not commonly used, we will focus on hydropneumatic accumulators.
Hydropneumatic accumulators feature two sections: a dry side containing compressed gas (usually nitrogen) and a wet side containing hydraulic fluid. The dry side is precharged with gas to a specific pressure based on system requirements. To prevent the mixing of gas and hydraulic fluid, a separating element—such as a bladder, diaphragm, or piston—is essential.
Bladder Accumulators
Bladder accumulators are the most prevalent type and utilize synthetic rubber, like nitrile, to contain the nitrogen gas precharge. The bladder is housed within a sealed cylinder with hemispherical caps. For optimal performance, these accumulators should be mounted with the liquid port facing downward and the gas port facing upward. As the accumulator fills with hydraulic fluid, the nitrogen-charged bladder compresses, storing energy based on the volume of fluid and precharge pressure. When downstream pressure decreases, the bladder expands, pushing the fluid out. While vertical mounting helps prevent uneven wear and trapped fluid, bladder accumulators can still perform well in any position if fluid contamination is managed properly.
Bladder accumulators are also easy to repair, with many manufacturers providing interchangeable rebuild kits for standard sizes. Most bladder accumulators are designed for bottom repair, but top-repairable versions are also available for easier maintenance in confined spaces. Top-repairable accumulators can be serviced while remaining installed, whereas bottom-repairable types must be removed for repairs.
Diaphragm Accumulators
Automotive Lift Repair Orlando Diaphragm accumulators use a synthetic rubber membrane to separate the gas and liquid sides. They can be either welded, non-repairable types or threaded, repairable types. The welded versions have a diaphragm bonded in the center and typically handle medium pressures, not exceeding 5,000 psi. In contrast, threaded diaphragm accumulators can achieve higher pressures—some reaching up to 10,000 psi—and allow for diaphragm replacement by unscrewing the two halves. These accumulators are usually compact, ranging from a few cubic inches to around 1 gallon in volume.
Piston Accumulators
Piston accumulators resemble rodless hydraulic cylinders, featuring a machined steel tube with caps at both ends—one for the oil port and the other for the gas port. Some models may have one end welded for better durability, while the other is threaded for repairs. Typically, Automotive Lift Repair Orlando piston accumulators are mounted with the oil port downward and the gas port upward. However, like bladder accumulators, they can function effectively on their sides if fluid conditions are well managed. It’s essential to monitor for contamination, which can accumulate at the bottom of the tube.