Applying Ultrasound Inspection to Diesel Engines

Internal combustion engines burn fuel and, regardless of size, they require air, preferably clean. The air we breathe is the same air engines breathe. No matter where we are on the planet, air contains particles in suspension. Some of these particles are harmless, but others represent a serious danger. Silica ranks as one of the hardest elements on earth, only surpassed by topaz, corundum, and diamond. Silica is very damaging if it reaches the inside of the engine. Silica also ranks as one of the most abundant elements on earth and ever-present in dirt and dust, which is made airborne in the conditions where mobile machines operate. Engines are therefore equipped with high-efficiency filtration systems to prevent silica and other contaminants from reaching the combustion chamber.

All diesel engines have primary and secondary filters fitted between the air intake vents and the turbocharger. When the engine is operational, a negative pressure is created in the air intake system, and any leaky orifice (loose clamps, cracked hoses, thinned metal, pinholes) downstream of the filters means the engine is breathing without filtration. This means air full of silica can reach the pistons, rings, sleeves, and other engine components, causing damage and premature failure. Depending on how much silica is ingested, the life of the engine is dramatically reduced, sometimes lasting only a few days!

Oil analysis is used as a predictive tool comparing the metal content and silica in parts per million (PPM) found in the oil sample against limit values set according to the engine manufacturer. The acceptable silica content is very low, ranging from 15 to 50 PPM. When a sample shows values over the limit, the source of the contamination needs to be found quickly and the mobile asset must be removed from service to avoid further costly damage. This introduces the added cost of downtime and lost productivity.

Finding the leaks calls for an exhaustive visual inspection of the entire air intake system. This can take several hours to inspect, and it’s not uncommon after the inspection to have found nothing. The next oil sample will still show high silica levels and increasing wear metal values, indicating the problem is getting worse. As a companion to visual inspection, ultrasound testing to find the leak will net results much faster and is also useful to confirm the repairs to the leak were done correctly. Progressive mobile mechanics use ultrasound inspection after any service work is made on the air intake system.