Return line & Suction Boost Filters
This type of filter has the advantage that the pump capacity (pressure and flow rate) installed in the steering and working hydraulics is implemented to supply the usually high-value drive hydraulics, which have a strict requirement for oil cleanliness, exclusively with filtered hydraulic oil.
In addition, dangerous operating conditions where negative pressure occurs on the suction side for the boost pump, is reduced to a minimum. Excellent cold start characteristics for the whole unit are the result. To enhance the economy of the whole unit, this space-saving return line & suction boost filter, which is usually installed as a “return line filter” on the hydraulic tank, provides the means of reducing the oil circulation volume by installing a smaller tank. In order to maintain the initial load of approx. 0.5 bar at the connection to the charge pump, a surplus of at least 10% between the return line volume and the suction volume is required under all operating conditions. Through the use of a pressure relief valve, when the ∆p reaches 2.5 bar, the oil flows directly into the tank (no bypass to the closed circuit). If, in addition to the flow from the open circuit, the leakage oil from the hydrostatic drive also goes through the filter, then the permitted pressure of the leakage oil at the filter must not be exceeded (taking into account the pressure drop of the leakage oil lines, of the oil cooler and the pressure relief valve) to protect the radial shaft seal rings.