Tiny particulates in lubricants that are invisible to the naked eye can have costly consequences in hydraulic systems.
By Zach Sutton, Chevron Lubricants Industrial & Services Sector Specialist
In the world of mechanical maintenance, machinery breakdowns are a reality.
Mechanical wear occurs constantly, and moving parts erode in quality over time. According to a study from the STLE and the National Research Council of Canada, 82% of mechanical wear is caused by particle contamination, making contamination one of the leading causes of hydraulic system failure. Additionally, it is common for machinery maintenance teams to ignore fluid cleanliness despite it being one of the major causes of breakdowns, leading to excessive downtime and lost profits.
The particles that damage system components the most are too small for humans to see with their naked eye — somewhere in the one to 10-micron range, or less than 10 times smaller than a grain of salt. These clearance-size particles enter the lubrication zone between machine parts and generate wear. Additionally, dirt and contaminants cause as much as 80% of hydraulic system failures, which can cost up to $100,000 per year.
Since many of these tiny particles are invisible to humans and exist within machinery, it can seem like a mission impossible to prevent them from causing damage to a system. However, there are plenty of ways to slow and mitigate mechanical wear in complex machinery, including routine maintenance and proper lubrication of the mechanical systems. Let’s explore how these particles cause damage to mechanical systems and best practices for avoiding them.
Tiny particles produce massive problems
Many machinery operators assume that any new oil they purchase will meet both the performance and cleanliness requirements set by the equipment manufacturer, but that’s usually not the case. End users often focus only on the performance specifications of new oil but do not examine how that oil will perform in a given component application. To achieve maximum component life, starting with new oil that meets the cleanliness specifications set by the original equipment manufacturer (OEM) is important.
Each time an oil is transferred, the oil can pick up more contaminants. In fact, it’s common for a lubricant to increase two to four ISO Cleanliness Codes — a measure of allowable contaminant particle size in a lubricant — during the distribution process. Typical new oil could contain up to 32 times more particles than the acceptable level. That’s because most typical new oil is not certified to meet a specific cleanliness level from the oil manufacturer or distributor at the point of delivery. Bulk oil can be transferred up to eight times on average before it reaches equipment, significantly raising the possibility of contamination in that lubricant.
It also doesn’t take much to contaminate clean oil. As little as one teaspoon of dirt in 55 gallons of oil could equate to as many as one billion particles that are four microns and larger. This level of contamination can be a double negative by generating wear and restricting the oil from protecting parts. Additives in the oil can be consumed by trying to manage the level of contaminants, which can lead to shortened oil life and equipment life.
The two leading types of contamination in oil are particulates and water. Particles typically enter a lubricant or oil after floating in the air, traveling through water vapor, or when transferring a lubricant. Catalysts for oil contamination, such as wear metals, water, and high oil temperature, all lead to oil degradation. The result is dirty oil, acid, sludge, and varnish formation within a machine’s component.
The most common causes of particle contamination within a machine are abrasion, erosion, and fatigue — all of which are caused by a combination of particulates or water breaching into a machine’s lubrication zone and adding pressure to that machine’s mechanical functions. Once they enter into a lubricant, these microscopic contaminates create wear, lead to costly equipment failures, and result in unstable operation.
While the sources and causes of machine decay are numerous and hard to protect against, there are still many ways to proactively defend systems against these damaging particles.
With uncertainty around an oil’s contaminant levels, many resort to pre-filtering oils themselves. However, this is a bad idea for several reasons. First, pre-filtering new oil can be expensive and a risk to the machinery. Consider the fact that purchasing and operating new filtration equipment spends additional budget. Add to that the costs for additional manpower to perform tasks that should be handled by a supplier. If someone unfamiliar with the process attempts to filter oil, they can over-filter it and remove important additives necessary for equipment success, so filtering should always be handled by a technical expert.
Often, companies purchase filtration equipment that is not designed for their applications, or their filtration systems are not properly maintained. Filtration results are also typically not measured or logged before or after the process when conducted on site. The end result is that oil filtration targets are rarely met, equipment suffers, and more contaminants are added to the oil.
Ensuring that any filtration is done by a technical expert is critical, but still, filtration can only do so much. Filters on equipment will remove some, but not all, contaminants — and in most cases, the damage is already done. By the time you recognize that oil is contaminated, the oil has likely already caused damaging wear to machinery. Many systems are not properly balanced or sized to exclude and remove the most critical clearance-sized particles, so even when oil is filtered, it can still carry damaging contaminants. Starting with clean new oil that meets the OEM specifications will ensure harmful particles are not introduced to the system and ease the tension for onboard filtration.
Protecting against pesky particles
Keeping hydraulics as clean as possible is the key to maximizing productivity and component life. To ensure a long, productive lifespan from components, pay close attention to the OEM’s machine component parts’ ISO Cleanliness requirements. A component’s sensitivity to contamination determines the maximum allowable particulate size in the lubricant, which in turn determines how clean the oil needs to be.
A good rule of thumb is that the oil should comport with a cleanliness level protecting the tightest machine clearance on the equipment. So, if a proportional control valve on a hydraulic system is the tightest clearance on a piece of equipment, then the ISO Cleanliness Code that the component requires would be the target level for new oil.
In addition to selecting the most appropriate oil for your component, you can ensure proper lubrication of your system by starting with clean oil and monitoring that cleanliness as it functions. Additionally, to ensure that oil remains clean, routinely replace dust caps on lubrication valves and oil filters to reduce contaminants and use certified oil transfer containers to keep oil clean and dry during transfer.
What matters most is that the system is healthy enough to function both currently and in the future. Avoiding breakdowns and managing a fully functional system starts by ensuring that oils and lubricants are appropriately graded and clean enough for their applications.
Filed Under: Components Oil Coolers, Filtration/Contamination Control, Fluid Conditioning, Fluids, Sealing & Contamination Control Tips