The air in most environments where a forklift operates is often contaminated with dust, pollen, mold and other elements that can be sucked into the forklift through its air intake. Quality Air Filters for a lift truck are mostly made of fibrous materials like paper, cotton or foam. The air filter makes sure that particulates in the air are kept out of the truck's working parts so they don't enter the engine's cylinders, contaminate the oil, cause mechanical wear and interfere with the forklift's operation.
Pleated paper is the most common material used for engine air filters because of efficiency, cost and ease of service. In some aftermarket air filters, oil-wetted polyurethane foam is the filtering material, especially where the truck operates in environments with a high level of dust. Air filters are designed to have an optimal working efficiency which includes having some dirt on the filter's surface. Some trucks have restriction indicators which tell you when it's time to replace the air filter.
With fuel-injection forklifts such as a Nissan, Yale, Caterpillar or Clark, the fuel injection pump's plunger has a very small tolerance. Any contamination can damage the plunger and cause an engine breakdown. Only a well-maintained fuel filter can make sure this doesn't happen.
Various oils are used in a forklift for its various functions. Hydraulic fluids enable the truck to lift heavy loads. Transmission fluids lubricate all the moving parts in the truck's transmission and are necessary for shifting. It is important that these different fluids are kept clean and contaminant-free at all times. For these, there are various hydraulic filters and transmission filters which must be replaced from time to time after they have reached their limits.
Another type of filter is a breather. It is a filter that makes use of silica and carbon to filter out not just solid contaminants but also water vapor. Sometimes, moisture in an engine or system can be more damaging than solid contaminants. In a breather, silica holds 40% of its weight in water and traps water vapor as it passes through. What does go through is filtered by a layer of activated carbon. https://www.parts-machining.com
Related reading: CAT 1G-8878 hydraulic filter OEM hydraulic Filter 184-3931
