Troubleshooting Failure in Sauer Danfoss S90 Pumps as Drive Motors: Loop Flush and Ot

[MikePhua]

Sauer Danfoss S90 pumps are commonly used as drive motors in various heavy equipment applications, including skid steers like the T300. However, when these pumps fail or encounter issues, they can significantly affect the machine’s performance and productivity. This article discusses common problems, the role of the loop flush, and potential solutions for dealing with pump failure in systems using Sauer Danfoss S90 pumps as drive motors.
Common Issues with Sauer Danfoss S90 Pumps

1. Pump Failure Due to Contamination
   Contamination of the hydraulic fluid is one of the most frequent causes of pump failure in Sauer Danfoss S90 pumps. Dirt, debris, and water entering the system can cause wear and tear on internal pump components, leading to failure. Contamination can also affect the performance of the entire hydraulic system, including drive motors.
   
2. Excessive Pressure or Load
   If the system experiences excessive pressure or overloading, it can lead to premature pump failure. Overloading may be due to incorrect settings or issues with the machine's load-sensing system. Running the pumps beyond their designed capacity can cause overheating, seal damage, and internal wear.
   
3. Improper Fluid Viscosity
   Using hydraulic fluid with improper viscosity can also cause issues in Sauer Danfoss S90 pumps. If the fluid is too thick, it can cause the pump to work harder, increasing the likelihood of overheating. On the other hand, fluid that is too thin can result in insufficient lubrication, leading to premature wear of pump components.
   
4. Cavitation
   Cavitation occurs when air bubbles form in the hydraulic fluid due to low pressure or high flow velocity. This can cause severe damage to the pump's internal components, including the gears and bearings, which ultimately leads to pump failure. Cavitation is often caused by improper fluid levels or a malfunctioning suction system.
   

The Role of Loop Flush
A loop flush is an essential maintenance procedure that helps clean the hydraulic system and restore optimal function. Flushing the hydraulic system regularly helps to remove contaminants such as dirt, debris, and old fluid that can cause pump failure. A loop flush is especially crucial in systems with Sauer Danfoss S90 pumps as drive motors, as any debris or contaminants in the system can quickly damage the pump and other hydraulic components.

1. Loop Flush Process
   During a loop flush, the hydraulic system is disconnected, and the pump circuit is flushed with clean fluid at a high flow rate. This ensures that contaminants are flushed out of the system and that the internal components of the pump are cleaned. The process can be done using a flushing machine or through manual procedures depending on the equipment setup.
   
2. Benefits of Loop Flushing
   • Prevents Contamination: Regular flushing helps to prevent contamination buildup in the hydraulic system, ensuring the longevity of pumps and motors.
     
   • Reduces Wear and Tear: By removing dirt, metal shavings, and other debris, loop flushing reduces the strain on internal components and minimizes premature wear.
     
   • Improves Fluid Quality: Flushing helps maintain fluid quality, ensuring proper viscosity and lubrication for optimal pump operation.
     

Additional Solutions for Preventing Pump Failure

1. Regular Hydraulic Fluid Maintenance
   Proper fluid maintenance is critical for extending the life of Sauer Danfoss S90 pumps. Regularly check the fluid levels and monitor the condition of the hydraulic fluid. It’s also essential to replace the fluid at the recommended intervals to prevent contamination and maintain proper viscosity.
   
2. System Pressure Settings
   Ensure that the system’s pressure settings are within the manufacturer’s specifications. Excessive pressure can strain the pumps and other hydraulic components, while too little pressure can result in inefficient performance. Regular pressure checks should be part of your maintenance routine.
   
3. Monitor Temperature
   Overheating is a common problem in hydraulic systems, especially in high-load applications. Ensure that the system is equipped with the appropriate cooling mechanisms to maintain optimal operating temperatures. Overheating can cause fluid breakdown and increase the likelihood of pump failure.
   
4. Check for Leaks
   Hydraulic leaks can cause a loss of pressure and fluid, which can lead to pump failure. Regularly inspect the system for leaks in hoses, fittings, or seals, and repair them promptly to prevent further damage.
   
5. Correct Fluid Viscosity
   Ensure that you are using the correct hydraulic fluid with the proper viscosity for your operating conditions. This ensures proper pump operation and reduces the risk of cavitation and excessive wear. Always follow the manufacturer’s guidelines for fluid specifications.
   

Conclusion
Sauer Danfoss S90 pumps play a vital role in drive systems, and when they fail, it can lead to significant downtime and repair costs. Common causes of pump failure include contamination, excessive pressure, improper fluid viscosity, and cavitation. Performing regular maintenance, including loop flushing, monitoring system pressure and fluid quality, and ensuring proper temperature management, can prevent these issues and extend the life of the pump and other hydraulic components. By staying proactive with maintenance and addressing issues early, you can avoid costly repairs and keep your equipment running smoothly.