"The paper machine dryer in our factory leaked too much oil, suspected of oil evaporation. The working speed was 360 revolutions per minute, the temperature range was 110 to 125 degrees Celsius, and it was equipped with a centralized oil lubrication system. The operator encountered this problem due to installation 12 additional drying cylinders using the same viscosity and the same oil (ISO VG 150). The temperature of the oil tank is about 72 degrees Celsius. There is less evaporation and no leakage before installation. I believe they need to switch to higher viscosity or synthetic alternatives, but in In this case, how do you choose the right lubricant?"

There are several things to consider. First of all, industrial lubricants with a viscosity of ISO VG 150 generally do not evaporate too much if exposed to temperatures as high as 125 degrees Celsius, because the flash point of these lubricants is above 200 degrees Celsius. The loss of lubricating oil may be due to leakage because there are more lines, connectors, and components in the system.

For proper lubrication, viscosity will depend on bearing conditions, including operating temperature, speed, load, bearing design and application method (in this case cycle). If the lubrication parameters remain the same, adding a drying cylinder to the system should not require a change in viscosity.

One possibility is that the operating temperature increases after the system expands. If so, it will definitely reduce the viscosity of the lubricant.

Although the viscosity grade of the lubricant you use is ISO VG 150, the most common viscosity grade for paper machines is ISO VG 220, which is the next higher grade in the ISO viscosity classification. With this in mind, you should confirm that you have been using the correct viscosity for the system. Even if the system was originally designed for ISO VG 150 lubricants, an ISO grade can be added without affecting the quality of the lubrication. Of course, this may just be a "patch" for problems with different root causes.

The sump size should also be calculated based on the system capacity and the maximum pump flow rate. The oil pan should have a minimum volume to maintain a stable supply of oil and allow the lubricating oil to remain in the oil pan for at least 5 to 10 minutes. This allows the final moisture or solid contaminants to settle as the heat is dissipated and foam is released.

When the circulation system is expanded to include more machines or components, it may be necessary to increase the sump capacity based on these new conditions. In addition, be sure to confirm the new oil level when the system is operating normally and after shutting down.

Lubricant manufacturers produce certain paper machine oils recommended for use in various machine types. Check whether your machine is suitable for a specific type of lubricant, and confirm that the lubricant you use is best for your application. 

Synthetic materials have many advantages, such as enabling you to increase energy efficiency or extend oil change intervals. Although switching to compositing may bring some benefits, it does not necessarily provide a solution because it will not solve the source of the problem. Therefore, the best strategy is to determine the cause of lubricant consumption, and then determine the best oil viscosity and formulation for your application. Then, your conclusion should allow you to take appropriate action.