PLATE 3608099 - Caterpillar

are used on machine fluid tanks and on bulk fluid storage tanks. Breathers are designed and sized to equalize the pressure differentials between the inside of the tank and the outside atmosphere. The yield strength of the fluid tanks is also one of the design criteria for breathers.At high temperatures, fluids may expand and create pressure inside tanks. Breathers allow the excess gas to flow from the tank to the outside, which relieves pressure buildup. Similarly, at low temperatures, pressure inside tanks may decrease and create a vacuum in the tank. Breathers in this case allow the ingression of external air to prevent tank collapse and at the same time filter the incoming air to keep the fluid clean. Breathers are also used to compensate for volume changes in the tank. For example, in hydraulic systems, when significant change of the length of hydraulic cylinders occurs quickly the change causes a sudden surge of oil flow into the hydraulic tank. This sudden flow of oil pressurizes the air in the tank. Breathers allow the pressurized air to escape from the tank, equalize the pressure, and avoid damage of the tank. Breathers are designed based on the tank size to allow the appropriate volume of gas flow in order to protect tanks. Breather design is also based on the rate of flow and the tank yield strength.Most breathers may have an integral filter element or a separate serviceable filter element. Filter elements in breathers prevent the ingression of dirt as the air moves into the tank. Filter elements also prevent the movement of fluids such as fuels or oils from the tanks and into the atmosphere, which reduces contamination.In general, breathers with filter elements are recommended for all fluid tanks. Breathers with filter elements are specifically recommended for use on fuel tanks, whether bulk or machine tanks. A four micron filter rating is recommended for these breathers to keep the fuels clean.Some breather designs require the servicing of the filter element only, while other designs require the servicing of the entire breather. Follow the instructions given in your Operation and Maintenance Manual for breather service life recommendations. Consult your Cat dealer for availability of breathers for your applications.