Pump Inlet Pump outlet Rotor Vane Weak spring Pressure adjustment Spring Bypass valve plate Insert Pin Pressure adjustment Vent connection to  fuel metering device  inlet air pressure Diaphragm Vent  chamber Pressure relief valve Inlet Outlet Figure 14-56.  A compensated vane pump is used in engine-driven  applications. The fuel metering device inlet air pressure is connected  to the vent chamber in the pump. The diaphragm assists or resists  the relief valve mechanism depending on the pressure sensed in  this chamber. Figure 14-54.  The pressure relief valve in a vane-type fuel pump. Figure 14-55.  The bypass feature in a vane-type fuel pump allows  fuel to flow through the pump during starting or when the pump  is inoperative. Figure 14-57.  Size comparison of 1-micron dust particle and  pin head.  14-33 A 1-micron dust particle on the head of a pin Pump Inlet Pump outlet Weak spring Bypass valve plate Fuel Filters pressure is greater than the outlet fuel press. The plate moves  down, and fuel can flow through the pump.  [Figure 14-55] Compensated vane-type fuel pumps are used when the vane  pump is the engine-driven primary fuel pump. The relief  valve setting varies automatically to provide the correct  delivery of fuel as the air inlet pressure of the fuel metering  device changes due to altitude or turbocharger outlet pressure.  A vent chamber above a diaphragm attached to the relief  mechanism is connected to the inlet air pressure source. As  air pressure varies, the diaphragm assists or resists the relief  valve spring pressure, resulting in proper fuel delivery for  the condition at the fuel metering device.  [Figure 14-56] Two main types of fuel cleaning device are utilized on  aircraft. Fuel strainers are usually constructed of relatively  coarse wire mesh. They are designed to trap large pieces of  debris and prevent their passage through the fuel system.  Fuel strainers do not inhibit the flow of water. Fuel filters  generally are usually fine mesh. In various applications, they  can trap fine sediment that can be only thousands of an inch  in diameter and also help trap water. The technician should  be aware that the terms “strainer” and “filter” are sometimes  used interchangeably. Micronic filters are commonly used on  turbine-powered aircraft. This is a type of filter that captures  extremely fine particles in the range of 10–25 microns. A  micron is  1/1,000  of a millimeter.  [Figure 14-57]