Usage:
3606 (8RB),
3608 (6MC),
3612 (9RC),
3616 (1PD) Engines Operating On Heavy Fuel And Equipped With A Vokes Fuel Filter
Reports indicate that some of these engines may typically be operating with the Vokes fuel filter priming valve in the middle position. This allows both filters to be used at the same time. This is not an incorrect operation, however it may not be optimal for the engine operator. When the engine is operated with fuel filter priming valve in the middle position and the differential pressure is allowed to reach the change level, a shut down of the engine may be required to change the filter elements.
Operation On One Side Of The Filter
Caterpillar recommends operating the engine with the Vokes fuel filter priming valve pointed towards one side of the filter during normal operation. This will allow changing the filter elements without shutting down the engine. When the maximum differential pressure is reached, the fuel flow can be simply redirected to the new filter element. This allows changing of the dirty side immediately without shutting down the engine. The newly cleaned side is now on standby for the next changeover.
Operation On Both Sides Of The Filter Simultaneously
Some operators prefer to operate on both sides of the filter housing simultaneously. While extending the time between filter element changes because each side handles only 50 percent flow, this may require an engine shutdown to change filter elements. In an intermittent operation, this may be preferable. However, in a continuous application where shutting down the engine is not desired, it may require switching all the flow to one side of the filter housing before the maximum differential pressure is reached to allow for a changeover during operation.
Both methods of operation are fully supportable in any application, as long as the guidelines are followed and the maximum differential pressure across the filter elements is not exceeded.
Filter Element Change Criteria
Caterpillar is also recommending a new change criteria for Vokes fuel filter elements. The former guideline was to change the filter element when there was a 70 kPa (10 psi) maximum differential pressure across the element. In accordance with recommendations from Vokes, Caterpillar is now recommending the filter elements be changed when a maximum differential pressure of 105 kPa (15 psi) is reached. This increase in maximum allowable differential pressure across the filter element will increase the service life of the filter elements. This will result in reduced operating costs associated with changing these filter elements.