Increase Decrease A B Figure 6-26. Oil pressure screen (A) and scavenge oil screen assembly (B).  Figure 6-25.  Removing oil temperature bulb.  Figure 6-27.  Oil pressure relief valve adjustment.  it is necessary to disassemble the filter for inspection and  cleaning. The manufacturer’s procedures should be followed  when disassembling and reassembling an oil screen assembly.  When reinstalling a filter or screen, use new O-rings and  gaskets and tighten the filter housing or cover retaining nuts  to the torque value specified in the applicable maintenance  manual. Filters should be safetied as required. An oil pressure regulating (relief) valve limits oil pressure to  the value specified by the engine manufacturer. Oil pressure  settings can vary from around 35 psi minimum to around 90  psi maximum, depending on the installation. The oil pressure  must be high enough to ensure adequate lubrication of the  engine and accessories at high speeds and power settings.  On the other hand, the pressure must not be too high, since  leakage and damage to the oil system may result. Before any  attempt is made to adjust the oil pressure, the engine must be  at the correct operating temperature and a check should be  made to assure that the correct viscosity oil is being used in  the engine. One example of adjusting the oil pressure is done  by removing a cover nut, loosening a locknut, and turning  the adjusting screw.  [Figure  6-27]  Turn the  adjusting screw Oil Pressure Relief Valve 6-17