19 March, 2018

What to know about solid contaminants

04 January, 2015
MP Filtri UK answers some commonly asked questions surrounding solid contaminants and how to keep your hydraulic fluid as clean and efficient as possible. What routines must be followed in order to minimise the chances of my hydraulic equipment suffering costly, premature component failures and unscheduled downtime? Six main routines must be followed: • Maintain fluid cleanliness; ISO 4406 /NAS 1638 etc. • Maintain fluid temperature and viscosity within optimum limits. • Maintain hydraulic system settings to manufacturers' specifications; e.g. ISO/NAS cleanliness for components, pressures etc. • Schedule component change-outs before they fail. Always bear in mind the anticipated life of component. • Follow correct commissioning procedures; including flushing and start-up procedures. • Conduct proactive analysis; regular monitoring, filter replacements, daily/weekly inspections etc. How can I limit solid contamination from entering my system? Good Housekeeping practices are essential. A few steps you can take to make an immediate difference include: • No food and drink near your process. • Pre-filter your new or used oil before placing into or returning back to the tank. • Use a dedicated funnel for that type of fluid for pouring into the tank. • Have a dedicated fill point for the reservoir. • Use a sloped or conical tank design with an outlet at the bottom so that contaminants captured by the first bank of filters • After filling or topping up with new oil, let the system flow and filter, reaching a natural equilibrium point before using live in your process. • Fit good quality breathers that are suitable for the application.3 micron or better. • Regularly replace the breathers, especially in harsh environments. How clean is clean? The answer to this question varies from customer to customer, depending on their requirements and system conditions. What can be said is that the decision to control contamination is normally based on the sensitivity of the components within the process (e.g. servo valves, actuators). There is widely publicised data on the clearances in these types of component and the cleanliness levels required. This information can also be found on the MP Filtri website. One of the main things that is overlooked in the industry is scale of cleanliness we are trying to control and measure. This is important to consider as it may change the way you choose to use your data to get a more realistic picture of system conditions over time. Below is a diagram showing the typical size particles we filter every day and measure with APC’s compared to common objects. It puts into perspective the challenge faced when designing a system. To eliminate all contaminants below a certain size is extremely difficult when you consider all the possible sources of contamination surrounding the system. Care should always be taken to select the right equipment and use suitable statistical methods when evaluating data, making decisions and taking action. What are the predominant types of contamination in my hydraulic system? This can vary considerably depending on the type of system and installation, but below are some typical types of contamination. By looking at the certain types, conclusions can often be drawn as to where the contaminant may be entering the system. Steps can then be taken to reduce the effects of such a contaminant… • Metallic — both ferrous and non-ferrous. • Silica (dirt, dust). • Silt. • Filter fibers. • Bacteria colonies. • Water. What effect does particulate contamination have on my system? Contamination can induce excessive stress on system components like pumps and valves as well as potentially clogging orifices, nozzles, and jets. One of the main areas of degradation is the formation of oxygenated & heavy polymeric compounds. These compounds are often in-soluble and settle out of the fluid as a gel or sludge. The creation of such compounds is accelerated in the presence of water and metal and so care should be taken to remove these types

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