Accumulator failures in hydraulic systems: hidden causes of production loss

Hydraulic accumulators can be neglected components of fluid power systems, but they play an essential part in maintaining the stability and efficiency. As a storage of energy, accumulators regulate pressure to absorb shocks, cushion the impact of shocks, help to prevent leaks, and also provide power for emergencies. If they fail, the consequences may not be immediately or apparent, but over time, they could result in substantial production losses, a rise in time to repair, and expensive repairs.

Knowing the causes behind the accumulator's failures is crucial for maintenance teams, engineers, and plant managers who wish to maximize the performance of their systems and minimize the risk of unexpected interruptions.

What is a hydraulic accumulator?

A hydraulic accumulator can be described as a pressure storage reservoir where hydraulic fluid is pumped into it through an external force, usually a compressed gas (usually nitrogen). The most popular types are:

• Bladder accumulators

• Piston accumulators

• Diaphragm accumulators

They can serve multiple functions. These devices can serve multiple purposes, including:

• Storage of energy and release

• Pulsation damping

• Absorption of shock

• Emergency backup power

• Compensation for leakage

Despite their importance, accumulators are often left out of maintenance programs, resulting in them becoming an unnoticed source of inefficiency.

Why accumulator failures go unnoticed

In contrast to valves or pumps, accumulator malfunctions do not usually cause sudden system shutdowns. They instead cause subtle performance issues that become worse with time. This includes:

• Longer cycle times

• More energy consumption

• Pressure changes

• Extreme wear on parts

Since the symptoms could be due to different parts that are involved, problems with accumulators tend to be undiagnosed until serious problems occur.

Hidden causes of accumulator failures

1. Incorrect pre-charge pressure

A major, frequent, and least understood cause of inefficient accumulator performance is the incorrect gas precharge pressure.

• A low pre-charge pressure decreases the capacity of energy storage and results in a slower system response.

• A high pre-charge pressure restricts fluid flow, which renders the accumulator unusable.

In time over time, nitrogen gas could escape through valves or seals and reduce the pre-charge pressure, impacting performance.

Impact on production

• Machine efficiency is reduced

• More frequent cycle times

• Higher energy costs

2. Gas leakage and permeation

Even with well-maintained systems, gas leaks can happen because of:

• Faulty charging valves

• Worn seals

• Permeation of bladder material

Bladder accumulation is particularly vulnerable to gradual loss of gas through permeation, especially in extreme temperatures.

Hidden effect:
The accumulator might appear to be operating, but its capacity for storing energy and releasing it is drastically diminished.

3. Bladder or diaphragm failure

The rupture of the bladder is a crucial failure type, typically caused by:

• Over-pressurization

• Chemical degradation of the elastomers

• Incompatible with hydraulic fluids

• Extreme temperature

When the bladder breaks, the gas and hydraulic fluid combine and render the accumulator ineffective.

Consequences:

• The loss of shock absorption

• More vibration

• The damage to valves, pumps, and piping

4. Contaminated hydraulic fluid

Fluid contamination is a significant factor in the failure of an accumulator. Dirt or water, as well as metal particles, could:

• Surfaces that are damaged internally

• Valve and block ports

• Increase the wear rate of seals

Contamination can also compromise the strength of bladder material, which can lead to premature loss of performance.

Production impact:

• More downtime as a result of regular maintenance

• The equipment's lifespan is decreased.

• Unplanned shutdowns

5. Temperature extremes

Hydraulic accumulations are sensitive to changes in temperature:

• Temperatures that are high increase seal degradation and gas permeation

• Temperatures below a certain temperature lower the viscosity of fluids, and impact the speed of response.

The thermal expansion and contraction could also affect the pre-charge pressure, which can lead to a lack of performance.

6. Improper installation

The consequences of installation errors could significantly decrease the life of your accumulator. Common errors include:

• Incorrect orientation of the mounting

• Insufficient support

• A weak connection to the hydraulic circuit.

For instance, putting the bladder accumulator horizontally, even though it was designed for vertical use, could result in irregular wear as well as premature breakdown.

7. Over-cycling and fatigue

In applications that are highly demanding, accumulation devices can experience frequent charging and discharge cycles. In time, this can lead to:

• The bladder is prone to fatigue due to the material or the diaphragms

• A decrease in elasticity

• Risk of rupture increases

Hidden loss:
The accumulator's efficiency decreases gradually and causes an increase in the load on motors and pumps.

8. Lack of preventive maintenance

A lot of facilities don't include the accumulators in their routine maintenance schedules. This can lead to:

• Undiscovered gas leakage

• Parts that are damaged

• Performance is degraded

Regular inspections and tests are vital to ensure proper operation.

9. Incorrect accumulator sizing

A fault-sized accumulator could result in several problems:

• Amount of accumulator too small - not enough storage capacity for energy

• Oversized accumulator - inefficient operation

Incorrect sizing can lead to an increase in stress on the system as well as decreased productivity.

10. Poor quality components

Utilizing accumulators that aren't of the highest quality or replacing parts could lead to:

• More rapid wear and tear

• Inconsistent performance

• The failure rate is increasing

Investing in top-quality components is crucial for long-term reliability.

How accumulator failures affect production

The failures of the accumulator rarely lead to one major breakdown. Instead, they trigger an inefficiency chain that affects production in multiple ways:

1. Increased energy consumption

If accumulators aren't able to effectively store and release energy, pumping needs to be more efficient, resulting in a higher amount of power used.

2. Reduced machine speed

The loss of stored energy can lead to slower actuator movement and longer time between cycles.

3. Equipment wear and tear

In the absence of proper shock absorption, the system components will experience more wear and stress.

4. Unplanned downtime

Minor problems can turn into major problems, leading to sudden shutdowns.

5. Product quality issues

Variations in pressure can impact processes that are precision, resulting in poor quality products.

Best practices to prevent accumulator failures

1. Regular pre-charge checks

• Monitor the nitrogen pressure frequently

• Make sure to use the right charging equipment

• Follow the manufacturer's recommendations

2. Fluid cleanliness control

• Use filters of the highest quality.

• Conduct a regular oil analysis

• Stop water pollution

3. Routine inspection

• Examine for corrosion, leaks, and physical damages

• Check connections and mountings

4. Temperature management

• Maintain the optimal operating temperature

• Use cooling systems if necessary

5. Proper sizing and selection

• Choose the appropriate size and type for the application

• Be aware of volume, pressure, and cycle requirements

6. Scheduled maintenance programs

• Include accumulation systems in preventive maintenance programs

• Replace worn parts before they fail

7. Use of monitoring systems

Advanced systems can monitor:

• Pressure levels

• Temperature

• Frequency of cycles

These systems can detect early warning signs of failure and avoid expensive downtime.

Early warning signs of accumulator failure

Early detection of symptoms can help prevent serious issues:

• Pumps are frequently cycled

• Variations in pressure or drops

• More noise and vibration

• Sluggish system response

• Leakage of visible fluids

The omission of these warnings can result in massive production loss.

Hydraulic accumulators are crucial, yet often neglected components of hydraulic power units. They aren't often a cause for concern, but they can erode the effectiveness of the system, add operating costs, and even disrupt production.

By understanding the hidden causes--such as incorrect pre-charge pressure, contamination, gas leakage, and poor maintenance--industries can take proactive steps to prevent failures. Regular inspections, correct measurement, and monitoring of the condition make sure that accumulators operate at optimum levels throughout their life.

In the end, putting time and money into accumulator maintenance isn't only about preventing breakdowns, but also protecting productivity, reducing costs, and ensuring the reliability of the system.