The influence of filters on the hydraulic systems of excavators

An efficient and adequately sized filter system must be an integral part of every hydraulic system. The presence of contaminants can cause premature wear on the internal surfaces of the hydraulic system, encourage leakage, and block the flow lines. 

Filters serve to screen larger or specifically sized particles out of hydraulic fluid to promote efficient machine operation.

Before going into detail about hydraulic filters, the advantages they provide, and the importance of correct maintenance and replacement, we will consider how the hydraulic system of an excavator works and what its most frequent faults are likely to be.

Getting to know a hydraulic system

The hydraulic systems of excavators comprise a large number and variety of elements, including:

• Valves
• Pumps
• Non-return valves for filters
• Counterbalance valves
• Hydraulic cylinders
• Pump filters
• Pipes and gaskets capable of resisting high pressures
  
  

All the elements that make up hydraulic systems must be extremely strong and durable.
Excavators also have at least six hydraulic actuators: 

• Arm
• Lifting arm
• Bucket
• Rotation
• Left movement
• Right movement
  
  

These diversified operating functions requires particular demands to the hydraulic system.

During operations an excavator's hydraulic system needs to drive all the movements fluidly, simultaneously, responsively, and independently.

High volume hydraulic fluid flows ensure quick movements during operation. This is achieved using differential cylinders with hydraulic flow rate classifiers of double the volume of the installed pump.

The fluid serves four basic functions in a hydraulic system:

• It generates force and movement to transform flow into pressure.
• It fills the gaps between various metal surfaces, creating a seal that helps exclude contaminants by forming a pressure barrier.
• It acts as a lubricant for various metal surfaces.
• It cools the system components.
  
  

Types of faults in excavator hydraulic systems

There are essentially three types of hydraulic faults:

• Catastrophic, when a large sized particle enters a pump or valve causing a shovel to jam.
• Intermittent, when contaminants accumulate in a trigger valve preventing it from closing.
• Degradation resulting from abrasive wear, corrosion, or surface fatigue of a component.
  
  

When particles enter the gaps between surfaces in a moving pump they can grind against the surfaces. This can cause stress and scratching, possibly even breaking up the pump components into metal particles.

If a cylinder does not have adequate gaskets for its rod, dirt may penetrate and damage the valves before being caught in a filter on the return line. Wear on the rod seals is normal since they become more rounded as they clear fluid from the rod or cylinder. If there is no intervention, the result will be a leaky cylinder allowing the penetration of dust and dirt. Rod gaskets must be replaced before they start leaking.

Vents allow adequate air movement inside the hydraulic reservoir, excluding atmospheric contaminants like dust and water drops. Those supplied as standard on heavy equipment are not always equipped with filtered vents.

Finally, to maximise the elimination of harmful particles, a breather equipped with a hydraulic filter should be installed.
 

How hydraulic filters work

The role of a filter is basically to screen the hydraulic system against foreign particles circulating in the fluid that could cause damage by abrasion. These particles can originate from external infiltration, wear inside the system, or they could derive from the production process.

Hydraulic filters are generally cylindrical devices with fluid inlets and outlets on opposite sides. The fluid is channelled through the filter seating and passes through the filter medium. The hydraulic filter retains contaminants while cleaned fluid moves through a central channel towards the outlet. Any contaminants remain trapped in the filter medium. 

The maintenance team is responsible for monitoring the filter system regularly and ensuring that it is working optimally. If the electronic or mechanical indicators signal that the filter is dirty or blocked, it must be immediately substituted.

The main advantages of hydraulic filters

A filter offers many advantages that help ensure the reliable operation of a hydraulic system, for example:

• Elimination of foreign particles in the hydraulic fluid.
• Protecting the hydraulic system from hazards deriving from particulate contaminants.
• Overall improved efficiency and productivity.
• Extending the useful life of the hydraulic system.
• Reduced maintenance costs.

Guidelines for changing filters

Establishing a routine preventive maintenance schedule is always the most practical and economical option. Regular filter changes enable excavators to run at maximum efficiency, keeping the hydraulic system clean and extending service life. 

• Follow the manufacturer's instructions for frequency of system maintenance, which is normally expressed in terms of work hours.
• Check your manufacturer's equipment manual for recommendations of filter pressure and efficiency parameters.
• Do not make do with the first filter that comes to hand! Filters made by reputable manufacturers are subjected to rigorous testing for performance and durability. A well-made, efficient filter will protect your most valuable machine components much longer and avoid the risk of unforeseen downtimes.
• Make sure that you keep an adequate stock of all your filter types so that changeovers have the minimum possible impact on productivity!

Choose ITR quality

The ITR range includes filters for all equipment brands and models, including:

• Hydraulic filters
• Oil filters
• Fuel filters
• Air filters
• Radial shaft seals 
• Gaskets

To learn about all ITR's products and get information or assistance, contact our experts!