Hydraulic accumulators are commonly found in industrial plants, often misunderstood despite their prevalence. While not inherently dangerous, they can pose significant risks if not properly understood. All accumulators store energy, making it essential to handle them with caution and respect.
Accumulator Functions
Automotive Lift Repair Orlando Hydraulic accumulators serve two main purposes: adding volume to a system quickly or absorbing shock, depending on their pre-charge. To increase system volume, the pre-charge should be slightly below the maximum system pressure to allow oil to enter. For shock absorption, the pre-charge should be near the maximum system pressure, keeping oil to a minimum inside the accumulator.
Pre-charging an Accumulator
Accumulators are typically pre-charged with dry nitrogen because it is safe, inexpensive, and chemically inert with hydraulic oil. Argon is another option, though costlier, while oxygen or air should never be used due to the risk of violent reactions with hydrocarbons, which can lead to explosions or fires. A charging rig is necessary for pre-charging, and it should be done without oil in the accumulator. Careful adjustment of nitrogen levels ensures the correct pre-charge, and this process can be monitored using a charging rig with a hose connected to a nitrogen bottle.
Avoiding Common Accumulator Failures
Automotive Lift Repair Orlando Accumulators can fail due to incorrect pre-charging. Overcharging can damage the bladder or piston by causing contact with internal components, while undercharging or failing to adjust pre-charge with system pressure can lead to reduced performance and potential damage. It’s generally better to undercharge than overcharge to avoid these risks.
Volume and Shock Absorption
Accumulators used for adding volume typically have a dump line to release pressure when the system is shut down. The pre-charge can be verified by observing the gauge as the system pressure drops. For shock absorption, bladder or diaphragm accumulators are preferred due to their responsiveness, while piston accumulators are less suited because of seal friction and mass.
Mounting Considerations
Automotive Lift Repair Orlando Accumulators should be mounted vertically when possible to prevent uneven wear or trapped fluid. Horizontal mounting, especially for bladder and piston accumulators, can cause damage over time.
Regular Inspections
Annual visual inspections of accumulators are crucial, especially in harsh environments. Look for rust, paint cracks, loose mounting points, or leaks. Accumulators should be removed and hydrotested every five years. Any damaged shells should be discarded and replaced, as repair attempts are unsafe.
Accumulators use nitrogen to maintain hydraulic fluid pressure. When fluid is pumped into an accumulator, the nitrogen (N2) inside is compressed. In high-pressure accumulators used in HHV systems, the nitrogen pressure can reach up to 5000 psi when full, while it remains around 2000 psi when empty. In the low-pressure reservoir, nitrogen pressure ranges from 60 psi when empty to 200 psi when full.
The EPA has employed two types of accumulators in their hydraulic hybrid systems:
Bladder Accumulator Type
In this design, Automotive Lift Repair Orlando hydraulic fluid compresses a nitrogen-filled bladder to generate pressure. High-pressure accumulators in HHVs operate between 2000 and 7000 psi.
– Advantage: High efficiency, with tests showing up to 97% energy retention.
– Disadvantage: Nitrogen permeates the foam bladder over time, requiring periodic recharging.
Piston Accumulator Type
Here, pressure is created by hydraulic fluid pushing a metal piston, which compresses nitrogen in a thin-walled metal shell.
– Advantage: Nitrogen loss is minimal, so recharging is not needed.
– Disadvantage: Slightly heavier and less efficient compared to the bladder model.
Hydraulic accumulators play a crucial role in many hydraulic systems, storing energy and releasing it as needed to enhance system efficiency.
What Is a Hydraulic Accumulator?
A hydraulic accumulator is a high-pressure component, typically gas-charged with nitrogen on one side and hydraulic fluid from the connected circuit on the other. As circuit pressure increases, the hydraulic fluid compresses the nitrogen, converting it into stored energy. This stored energy may be used for damping or released at a later time.
The accumulator’s exterior is made from materials like steel or titanium to withstand system pressures, while the interior houses a piston, bladder, or diaphragm to compress the gas at a precharged pressure.
How Does a Hydraulic Accumulator Work?
The Automotive Lift Repair Orlando accumulator starts in a precharged state with nitrogen occupying most of the space inside. As hydraulic fluid enters, it compresses the nitrogen, reducing its volume. The fluid then fills the chamber, causing the internal piston, bladder, or diaphragm to move.
In applications where the accumulator stores energy for later use, a pilot-operated check valve is often present. This valve allows the accumulator to pressurize but only releases the fluid when pilot pressure is applied. Once released, the pressurized nitrogen drives the fluid out until a balance is reached or all fluid has been expelled.
This cycle of precharging and charging continues until the system shuts down. If the accumulator is charged when the system is turned off, it remains charged, making caution necessary during maintenance.
Functions of a Hydraulic Accumulator
Automotive Lift Repair Orlando Hydraulic accumulators perform two main functions:
1. Adding fluid volume: They quickly add hydraulic fluid to the system to increase pressure when it drops.
2. Damping shock: Smaller accumulators with lower precharge pressure absorb shocks in the hydraulic circuit.
Types of Hydraulic Accumulators
Bladder Accumulators:
These contain a nitrogen-filled bladder that is compressed as hydraulic fluid enters. The compressed bladder then expands to push the fluid out when pressure increases. While highly efficient, they require periodic recharging as nitrogen may slowly leak through the bladder.
Piston Accumulators:
In this type, nitrogen is contained in a cylinder on one side of a piston, which moves as hydraulic oil enters the accumulator. When system pressure increases, the nitrogen pushes the piston back, expelling the fluid. Piston accumulators are simple and can be more compact, though they require more seals than other types.
Diaphragm Accumulators:
Similar to bladder accumulators, Automotive Lift Repair Orlando diaphragm accumulators use an elastic diaphragm to separate the gas from the fluid. They can handle higher pressure rates, are lightweight, economical, and responsive, making them ideal for mobile hydraulics and shock absorption.
Diagnosing and Resolving Hydraulic Accumulator Issues
If system pressure or efficiency drops while other components function properly, the issue may lie with an accumulator: