What is the meaning of cav filter?

Answer 1

C.A.V. are the initials of the owner (Charles Anthony Vandervell) of a company that invented a simple, cheap, replaceable (throw-away) fuel filter. The company was taken over by Lucas Industries (later the mechanical division was renamed Delphi Inc). Originally CAV filters were intended mostly for tractors but are now also used in trucks and 4WDs everywhere. The whole CAV 'system' is in 4 parts - 1. The head/top has inlets and outlets, a bleed port and mounting holes to bolt onto your vehicle/engine/chassis, etc. There is a central exit pipe for filtered fuel to rise up from below which has a long, thin bolt hanging down through its centre. 2 gaskets are fitted to the bottom of the head, one on the outside of the central outlet pipe and one in a groove around the outer edge of the whole unit. 2. The 'throw-away filter' itself is a can with lots of holes in the top and bottom. A tube through its centre fits over the outlet pipe in the head unit and is sealed by the central gasket mentioned above. The outer edge of the filter is sealed by the outer gasket in the head unit. Fuel coming into the unit therefore must pass through the can which is filled with a specially impregnated paper that also has a carefully controlled pore size. 3. A glass sight bowl with a drain port is clamped by the centre bolt below the filter. A perimeter gasket in a groove around the outer edge of the bowl seals the outside to the filter while a small o-ring seals around the central bolt (under a washer on the outside). 4. [Not always present] Between the filter and the glass bowl an upside-down plastic 'tree' attracts and holds tiny water droplets so that they are prevented from being passed up the central pipe and out of the filter assembly. The minute droplets join together (agglomerate) and drop to the bottom of the bowl where they can be drained out periodically. The special paper and the agglomerater work together to extract water from the fuel. Running the filter backwards defeats the purpose of the coating and agglomerater by pumping the small water droplets through and directly out the top of the filter unit. The small pore size of the paper removes fine, suspended particles from the fuel either way. This filter is NOT designed to separate large particles or large drops of water from the fuel (although it still does do this, and it will clog very quickly). Good fuel tank design and good fueling practice should keep the larger particles out of the final filtration path which is where the CAV system is designed to perform a final 'polishing' of the fuel. Cheap CAV filters used after a cheap, coarse pre-filter and a water trap provide superior filtration to protect engine parts from abrasive particles and disruptive water. The sight bowl with its water drain are not only reassuring when it remains empty, but a very simple warning system when it starts to fill. Many vehicles fit a (cheap, throw-away) CAV filter between the coarse filter (located near the tank) and the final filter (located on the engine). Often the engine's final filter (usually expensive) lasts several manufactures' replacement periods and is only changed when the operator becomes paranoid about leaving it on for yet another 5000km! bruceg 8-2009