New Oil-Circulation System Boosts PM Lube Efficiency at UPM Mill

A new type of oil circulation system in operation at the UPM Tevassari mill in Valkeakoski, Finland, for more than a year now has significantly improved paper machine lubrication efficiency. Based on results from the system installed on No. 5 paper machine, the mill has decided to install a similar system on its other paper machine.

At the heart of the new lubrication system, developed by Safematic, is a revolutionary oil reservoir design that achieves operating efficiencies of more than 90%, compared with less than 40% with traditional reservoirs. The compact reservoir volume is only one-third to one-half that required with traditional systems, which was a primary consideration at Valkeakoski, according to Markku Sironen of the mill's maintenance department.

Sironen explains that because the mill was undertaking a project to speed up PM 5, it wanted to modernize the oil circulation system as well. Space available for a new oil pumping station was limited due to the machine rebuild, he points out, and thus size was important.

The mill also chose to go with the new Flowline system because of its long-term relationship with Safematic and its interest in being involved with the system's development from the ground floor up, Sironen points out. And, of course, he adds, the mill wanted to pass any benefits of the new technology on to its customers.

In addition to the new reservoir design, the Flowline system consists of other modular components, including the pumping unit, a control unit, a variable frequency a.c. drive, and piping. It also includes a new vacuum dehydrator and a digital flow monitoring system.

System Design and Operation

As Kalevi Korpi, VP of lubricating systems for Safematic in the Atlanta, GA., area, explains, the pulp and paper industry uses circulation oil lubrication at points where the oil lubrication also cools and cleans them. The lubrication system must be able to deliver the right amount of high quality oil to each lubrication point. It also has to work at high temperatures and eliminate contaminants such as abraided particles, oxidized particles, water, and air bubbles, he emphasizes.

In traditional system, less than half of the oil is in circulation. The calculated retention time of the oil (according to fixed sizing) stays about 10 minutes—at best—which is not long enough to remove impurities, Korpi says. In recent years, considerable research has been aimed at increasing the oil retention time, but most of these efforts have focused on increasing the size of the reservoir, and not improving actual efficiency of the oil usage, he points out.

As depicted in Figure 1, a series of concentric platelets in the new, round reservoir provide a much shorter distance for air and water to travel after separation, compared with the large, rectangular chamber in traditional reservoir designs. The smaller oil reservoir (e.g. 2,000 liters instead of 6,000 liters in previous designs) leads to greater efficiency and better lubrication.

In addition to that removed in the newly designed reservoir, water and air can be removed from the system by the online Flowline Vac vacuum dehydrator depicted in Figure 2. The unit can also be installed into existing oil circulation systems. In fact, the capability of adding the vacuum dehydrator into its existing system was also a key consideration at the UPM mill, Sironen says.

Figure 3 shows typical lubrication oil recovery after water shock, using the Flowline system. As shown, the system's complete water content jumped up to 1,600 ppm and returned to a level of 200 ppm after system recovery during an 18-hr period.

Conditions for this figure are:

With continuous water input of 4.8 gal/24 hr, complete water content remains at a level of 200 ppm, using the same flow of 70 gpm and an oil capacity of 740 gal. In both cases (water shock and continuous water input), water content was measured using a UCC H₂Oil Analyzer.

The Safematic control system features flexible modular construction and an automatic startup mode. The interface between the unit and options such as the vacuum dehydrator and sump units is easily accessible. External communications with other process control systems is available through the Modbus protocol.

The Flowline monitor (Figure 4) shows the amount of flow at all lubrication points at a glance. With the help of the Flowline Hub control unit, meters can be connected either directly to the Safematic user interface or to the SRRC (Safematic remote runnability control) family of control products by modem to become a part of the remote monitoring of the company's central lubrication and sealing systems.

The monitor can be extensively adjusted for small amounts of flow, and it has a wide adjustment range (parameters set at the flow tubes are readily visible). It also features a practical and clear SFFI LED indicator system, alarm trends follow-up, electronic temperature measurement, and temperature-compensated flow rate measurements.

Sironen reports that if there is water leakage, the water content can be easily seen and can be removed quickly. He adds that pressure can be easily adjusted using the variable frequency a.c. drive. Overall, Sironen says, the mill has realized significant savings in lubrication oil, both new and waste oil, using the system during the past year.

By Ken Patrick