What is the best way to clean the shell side of a shell and tube oil cooler? There is a suspicion of sludge buildup and carbon from the oil. The oil is used for a screw compressor."
This is the mildest of the flushing strategies. Because many machines have no onboard filtration, the use of periodic filter carts and oil reclamation equipment not only can clean the oil (drawing down the contaminant level) but can also remove loosely deposited sludge and sediment from the shell.
These are chemically active compounds, typically caustics and acids, that aid in the removal of the most adherent organic and inorganic surface deposits. The oil must first be removed completely from the system. Following the flush, these chemicals should be thoroughly rinsed from the system, often followed by pacification. Always consult machine and lubricant suppliers before employing chemical flushes.
This generally involves the use of scrapers, brushes, abrasives and sometimes an ultrasonic bath. Often, chemicals are also used as the machine components are washed one at a time using a parts-cleaning station.
Besides experience, an important part of defining the correct strategy and tactics comes from the inspection of the machine and contaminants. This inspection should be repeated before a machine is returned to service to verify that a successful flush has been achieved. Likewise, a final oil sample should be taken and analyzed to confirm that residual flushing fluids or loosened deposits that could potentially compromise lubrication and system operation don’t remain in the new oil.