Exhaust Systems in Diesel Generators: What You Need to Know?

Diesel generator sets play a crucial role in many industrial and commercial scenarios, especially when power supply is unstable or backup power is required. However, to ensure the stable operation of the generator set and extend its service life, maintenance of all its components is essential. Among them, the maintenance of the exhaust system is often overlooked, but it has a crucial impact on the overall performance of the generator set and emission control. This article will provide a detailed introduction to the components of the diesel generator set exhaust system, key maintenance points, and some practical operational suggestions to help you better manage and maintain this critical system.

The exhaust system of a diesel generator set consists of several important components. These components work together to ensure that exhaust gases can be discharged smoothly and with low noise while reducing environmental pollution. The main components include:

The water-jacketed exhaust pipe is an important part of the exhaust system. It connects with the cooling system of the explosion-proof diesel generator through the coolant in the water jacket, forming a closed-loop cooling system. This design effectively controls the surface temperature of the exhaust pipe, usually not exceeding 150°C. Connections between components are made with rubber hoses that link the water jackets, forming a smooth circulating water path.

The water-jacketed bellows is located between the diesel generator and the exhaust treatment box, mainly serving as a vibration absorber. The bellows design can effectively absorb vibrations generated during engine operation, reducing the impact on other components and thus extending the service life of the entire exhaust system.

The exhaust treatment box is one of the core components of the diesel generator exhaust system, containing multiple important functional components. Among them, the exhaust flame arrester is a key part used to extinguish flames in the exhaust gas. It is made of multiple stainless steel plates, each 1.2mm thick and 51mm wide, stacked together, with gaps between plates not exceeding 0.5mm. This design can effectively extinguish flames in the exhaust, preventing flame propagation and improving the overall safety of the system.

In addition to the exhaust flame arrester, the exhaust treatment box also contains a water bath and an expansion chamber. The water bath further cools and cleans the exhaust gas, removing soot and dissolved harmful substances. The exhaust gas, after water bath treatment, enters the expansion chamber and is finally discharged into the atmosphere through the tailpipe. This process not only lowers the temperature of the exhaust but also reduces environmental pollution.

Besides the main components mentioned above, the diesel generator exhaust system also includes exhaust pipes, mufflers, turbochargers (if applicable), and other components. The exhaust pipe channels the exhaust from the engine, the muffler reduces exhaust noise, and the turbocharger increases engine power by boosting intake pressure. These components work together to ensure the efficient operation of the entire exhaust system.

After understanding the components and key maintenance points of the diesel generator exhaust system, we now look at installation and layout recommendations. Proper installation and layout not only ensure the efficient operation of the diesel generator exhaust system but also prevent many potential issues, improving the performance and safety of the entire generator set.

To absorb thermal expansion, generator displacement, and vibration, the engine exhaust outlet should be connected to a properly sized stainless steel expandable bellows. For large generator sets, it is recommended to install bellows of 24 inches (610mm) or longer; for small generator sets directly fixed to the floor, the exhaust outlet should have bellows of at least 18 inches. It should be noted that bellows must not be used as elbows or to compensate for pipe installation errors.

To reduce condensation corrosion, mufflers should be installed as close to the engine as possible for rapid heating. Mufflers and exhaust pipes should be supported by hangers or brackets; do not use the engine exhaust pipe for load-bearing, as this may damage the engine exhaust pipe and reduce the turbocharger's lifespan.

Exhaust pipes are recommended to use black iron pipe with elbows as large in radius as possible. Provided the engine exhaust pipe bending pressure limits are met, it is recommended that the nominal diameter of the entire diesel generator exhaust system pipeline match the engine exhaust outlet as closely as possible. Pipes smaller than the exhaust outlet are prohibited, as larger pipes are less susceptible to condensation corrosion and prevent exhaust expansion that can cause power loss. The smaller the diameter change of the diesel generator exhaust system, the smaller the friction loss.

It is recommended to implement thermal insulation on all mufflers and exhaust pipes to avoid accidental ignition or triggering of automatic fire suppression devices, reducing condensation corrosion and heat radiation in the generator room. Unless the coolant temperature is very low, do not insulate the engine exhaust pipe and turbocharger housing, otherwise high temperatures may burn the exhaust pipe and turbocharger housing.

Exhaust pipes should maintain at least 9 inches (299mm) of clearance from flammable materials. When passing through walls and ceilings, exhaust pipes should be equipped with fireproof sleeves or insulation.

The diesel generator exhaust system outlet should be installed away from buildings and air inlets to prevent soiling walls and windows. It is recommended to install the exhaust system on the leeward side of buildings and as high as possible to facilitate exhaust discharge. Certain standards stipulate that the exhaust pipe outlet should be at least 3 meters above the ground, 1 meter away from exterior walls or roofs, 3 meters away from building entrances, and at least 3 meters higher than nearby buildings. Vertical exhaust outlets should be fitted with rain guards.

The generator set must not share the diesel generator exhaust system with other equipment (including other generators). Smoke, corrosive condensate, and high-temperature exhaust must not damage shared equipment.

Exhaust backpressure must never exceed the limits specified in the engine manual. Generally, it is 20–50 mbar. Excessive backpressure can produce high-temperature exhaust and smoke, reducing engine power and service life. Therefore, before determining the diesel generator exhaust system layout, the engine exhaust backpressure should be estimated, and the backpressure at full-load operation should be measured before commissioning.

After understanding the components of the diesel generator exhaust system, we now discuss the key maintenance points. Maintenance is crucial for ensuring the efficient operation of the exhaust system and extending the service life of the generator set. Regular maintenance can not only reduce the probability of faults but also improve system safety and environmental performance.

The exhaust flame arrester is a key safety component of the diesel generator exhaust system, and its cleaning and maintenance are critical. To ensure smooth exhaust flow, debris and soot between the arrester surfaces and gaps should be cleaned promptly. Daily cleaning is recommended. During cleaning, open the maintenance door, loosen the top clamp, and remove the arrester. Use appropriate tools to remove soot and debris from both surfaces of the arrester, reinstall, tighten, and close the maintenance door. Special attention must be paid not to damage the gaps between the arrester plates to ensure normal function.

The water level control in the exhaust treatment box is crucial for normal system operation. The water volume in the exhaust treatment box is about 50 liters, controlled by an inlet float valve and a water level alarm float. The inlet float valve controls the water level and replenishes water from the tank when insufficient. The water level alarm float triggers an automatic protection alarm and shuts down the explosion-proof diesel generator within 1 minute if the water level drops below control and the tank cannot supply water. Therefore, before operation, the water tank must be filled, and water levels must be monitored during operation to ensure normal operation.

The exhaust pipe is the main channel for exhaust gas discharge, and its smoothness and integrity directly affect engine performance and emission control. Over time, carbon and resin can accumulate inside the pipe, blocking exhaust flow. These deposits should be cleaned regularly using wire brushes, blunt scrapers, or chemical soaking to soften them. Care must be taken not to damage the inner wall during cleaning.

Exhaust pipes may also develop cracks, perforations, or deformation over time, which can cause exhaust leakage, reduce engine performance, and pollute the environment. Regular inspections and, if necessary, repairs via gas welding or electric welding are recommended.

All connections in the diesel generator exhaust system must be tight to prevent exhaust leakage. During inspection, any looseness or leakage should be addressed immediately by tightening or replacing gaskets. Flange gaskets are made of copper-clad asbestos boards with good elasticity. If the gasket is damaged or loses elasticity during disassembly, it should be replaced. Ensure that all sealing surfaces are free from scratches or damage to guarantee sealing performance.

Exhaust pipes are prone to corrosion in high-temperature and humid environments, which can reduce their lifespan and affect exhaust performance. Regular inspection and application of anti-corrosion measures, such as protective coatings, are necessary to extend service life.

For diesel generators equipped with turbochargers, regularly check the rotor mobility, seal integrity, and bearing lubrication. Any abnormalities should be addressed promptly to ensure normal turbocharger operation and improve engine power and performance.

Although the diesel generator exhaust system is only part of a diesel generator set, its importance cannot be ignored. Regular maintenance and proper installation and layout not only ensure smooth and intact exhaust operation but also improve engine performance, reduce environmental pollution, and extend the service life of the entire generator set. The maintenance points and installation recommendations presented here aim to help you better manage and maintain the diesel generator set exhaust system, ensuring stable operation and providing reliable power supply.