In a hydraulic system, fluid performs four basic functions:
- It creates force and motion as flow is converted to pressure.
- By inhabiting the space between metal surfaces, the fluid forms a seal which provides a pressure barrier and helps exclude contaminants.
- Lubricates metal surfaces.
- Cools system components.
If any one of these functions is diminished, the hydraulic system will not performed as designed. Worse yet, catastrophic failures are possible. The resulting downtime can easily cost a manufacturing plant thousands of dollars per hour. Aside from human error, the most common source of system failure is fluid contamination; it is estimated that up to 90% of hydraulic failures result from contaminated fluids. Contamination can consist as solid particles, water, air and reactive chemicals, which all damage fluid functions in one way or another.
Sources of Contaminants
Contaminants enter hydraulic systems in a variety of ways.
Built in during the manufacturing process: dirt, welding slag, rubber particles from hoses and seals, sand from castings, rust and metal debris from machine components.
When a fluid is added to the system: a certain amount of contamination usually comes with fluids when they are added to the system. New oil is not clean, and you should never add a fluid without filtering it first. A good tool for this is a filter/transfer cart.
Internally generated during normal operation: without getting into film thickness, viscosity indexes, etc., system operation generates internal contamination. This occurs as part of normal component wear. For example, the constant rotation of pumps is a major source of contamination.
Ingested from outside the system during normal operation: contaminants also enter through breather caps, imperfect seals and other openings. Cylinder rods are an obvious source of ingression.
Without preventive measures and fluid conditioning, negative effects can escalate to the point of component failure, causing dreaded downtime. We’ve covered what happens when and how contaminates get into a hydraulic system. Now what can we do to minimize it?
As mentioned above, an endless program to minimize and remove contaminants must be implemented. As a first step, it’s suggested that you perform an oil analysis to find out what types of contaminants are present in your fluid. You must collect samples from each piece of equipment, as types of contaminants can vary from piece to piece. As a bonus, you might be able to determine an eminent component failure from the results of your analysis. For example, brass particles in your fluid usually mean that pump failure is inevitable. In this case, you would be able to replace the pump before a catastrophic failure occurs, saving you from higher repair costs and costly downtime.
Steps you can take to maintain a clean hydraulic system include:
- Making sure that the area around the reservoir is clean.
- Performing a complete flush of all systems before initial start-up.
- Changing hydraulic filters and fluids on new equipment after the recommended break-in period, or sooner.
- Making sure to use a quality breather on your reservoir (not the little chrome ones).
- Ensuring that the fluid being added to your system is filtered to specifications before or during addition.
- Periodically filtering all the fluid in the reservoir with a filter cart in a kidney loop fashion.
- Performing fluid analysis tests on a regular basis and when you suspect contamination.
- Making sure to use quality BETA 1000 (99.9% efficient) elements in all filter housings, and changing them as needed.
- Making sure hydraulic hoses are plugged when replacing or repairing your system.
- Repairing leaks as soon as possible.
Keeping your hydraulic systems clean is no small task, but it will pay for itself tenfold if you implement a plan and stick to it.
Contact Kaman Fluid Power to speak with a hydraulic filter specialist today to learn more.
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