The turbocharged, four-stroke, diesel generator set drive engines on your vessel are protected with dry-type air intake filters. The filter element condition can be evaluated by attaching a water manometer to measure the vacuum in the air duct between the air intake filter and the turbocharger blower inlet. Assume that the manometer reads 10" of water column (negative) at rated engine rpm under full load with a clean, properly sealing filter element. What would a reading of 20" of water column (negative) indicate at rated engine rpm under full load?
• Intake restriction and vacuum: How a dirty air filter affects pressure in the intake duct on a turbocharged diesel. • Baseline reading with a clean filter: 10 inches of water column (negative) is given as the normal value at full load and rated rpm. • Bypass vs restriction: How a leak around the filter seal would change vacuum compared to a restriction through the filter media.
• If air has a harder time getting through the filter media, what happens to the vacuum (negative pressure) between the filter and turbo inlet at the same rpm and load? • If the filter were leaking around the seal (bypassing), would you expect the measured vacuum to increase, decrease, or stay the same compared to the clean, properly sealed value? • Is a change from 10" to 20" of water column a small change or a large change in restriction, and what does that suggest about the filter’s condition?
• Compare the direction and magnitude of change from 10" (clean) to 20" and what that means for flow restriction. • Decide whether a bypass leak would make the engine ‘see’ more or less restriction than normal at the measuring point. • Determine whether such a change would call for immediate attention or deferred maintenance based on severity.
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