WorldWide Drilling Resource

73 WorldWide Drilling Resource ® MARCH 2015 Hydraulic Training by J. Eric Freimuth Hydraulic Training Associates Revisiting System Cleanliness Part 5 In this issue, we will discuss the importance of filter placement. Filter placement is critical for main- taining acceptable fluid cleanliness levels and adequate component protection, reducing machine downtime. Filter breathers are critical in preven- tion of airborne particulate ingression. As the system operates, the fluid level in the reservoir changes. This draws in outside air, and with it, airborne partic- ulates. The breather filters the air enter- ing the reservoir. Pressure filters are often required to protect the component immediately downstream of the filter, such as a sen- sitive servo valve, from accelerated wear, silting, or sticking. Pressure filters must be able to withstand the operating pres- sure of the system, as well as any pump pulsations. Return line filters are neces- sary to provide for total system cleanli- ness. They can trap very small parti- cles before they return to the re- servoir. They must be sized to handle the full return flow from the system. A kidney loop or off- line filtration is often required when fluid circulation through a return filter is min- imal. Being independent of the main hydraulic system, off-line filters can be placed where they are most convenient to service or change. It is normal for off-line filtration to run continuously. Understanding the components of all filters in a filtration system is critical. The head of the filter is the component attaching the conductors to the filter. A bypass check valve is most commonly supplied in the head. The purpose of this check valve is to prevent back pres- sure in a system. The tension spring for the check valve is usually supplied by the manufacturer and comes in various strengths. The check valve will open once the filter element is sufficiently plugged with contaminants from the upstream system. The check valve will allow oil to by- pass downstream. The more the filter is plugged, the more the check valve will open to allow more oil to bypass. Once the filter element is replaced, the bypass check will once again close, forcing the oil to pass through the filter element. One of the most neglected compo- nents of filter is the indicator gauge. All filters should have an indicator gauge installed on the head. The purpose of this gauge is to inform the operator or mechanic of the condition of the element. The gauge will have three bands: red, yellow, and green. Eric michele@ worldwidedrillingresource.com --- *+ )#)('-()$* !(& )(%#'" +)""+ ,'.*,+ -'"/ 0 . 1 1 1 1