True Luber Driveshaft - Continuous U-joint Lubrication

Tommy Daniels
Tags: industrial lubricants

Idcon, a reliability and maintenance management consulting firm, came to our pulp and paper mill about nine years ago and started us on a reliability program that has changed our maintenance department completely.

Figure 1

Change in Maintenance Mentality

Christer Idhammar came to our mill and told us to take some craftspeople out of our “firefighting” crews and put them on special reliability projects – to let them walk around to lubricate and inspect machines while they were running. He recommended we put windows in our guards and inspect them with strobe lights. He also advised us to buy small temperature guns to monitor potential heat problems.

Today, our maintenance department is smaller and more efficient than in the past. We have eight people who perform the essential care monitoring (ECM) and lubrication on a daily basis; four vibration analysis people; three dedicated people who are running hard piping to all three paper machines so they can be lubricated on-the-run; and four people in a pump rebuild shop.

In our quest to improve reliability and with the implementation of the ECM program, we have completely changed the way we do business. Good decision-based data is now stored on the majority of our equipment.

The work performed by foremen of the various areas is now driven by the monthly reports generated from the reliability department. Machinery is now repaired in the early stages before catastrophic damage. This allows the machinery to be salvaged and repaired at a considerable cost savings.

Lubrication Issues

As our reliability program was getting off to a strong start, we noticed numerous paper machine driveshaft failures were occurring. The reliability group knew that on average, we were losing five driveshafts each year.

The driveshafts took an average of four hours to change. The cumulative cost of the parts, labor and lost operating profit totaled to about $336,000 per year. The engineering services department at our paper mill determined a lack of lubrication to be the root cause of these costly failures.

The Solution

Our investigation into lubrication frequencies for driveshafts discovered that large truck fleets, upon servicing their trucks, required truck driveshafts to have grease exit out all eight bearing seals when they were greased, or the shaft was replaced.

This information is also in most of the literature supplied with new driveshafts. U-joint manufacturers also recommend lubrication every 200 to 500 hours of continuous operation. Because shutting down the machines every eight to 20 days was not attractive, the decision to lubricate the driveshaft bearings and the rest of the machine on an eight-week schedule was adopted.

The new rule was that grease must exit each seal. If not, the driveshaft was replaced. The trunnion bearing failing to accept grease was marked with paint so if the driveshaft failed before it could be changed, we could identify the lack of lubrication as the culprit.

Since then, only two driveshafts have been lost. When the driveshaft failures had been nearly eliminated, we focused on reducing the number of hours required to accomplish the necessary lubrication.

Large air-powered grease guns are now placed along the machine where the crews start on a lubrication outage day. The guns are tagged with the name of the crew and extra grease containers are placed for easy replenishment as required. Careful supervision is given to the crews. As some finish early, they work in other areas of the machine.

None of the lube crews leaves until the machine is complete. Hard-piped grease lines, replacing the driveshaft guards with new easy-to-open access doors, and efficient management of the crews resulted in reducing the lubrication time per outage from 12 hours to eight hours.

Improving Lubrication Application with Automatic Lubricators

As management is never satisfied with the number of people we use during an outage, we were asked to reduce the number of contractors. The grease crew was asked to work even more efficiently and give back some craftspeople to replace the lost contract people. The main time-consuming task during a lubrication outage was greasing the driveshafts.

Even with easy-access doors on the new aluminum guards, our largest machine took four people (two crews) eight hours to grease the driveshafts. As the automatic system on the market was too expensive and too time-consuming to install, we needed a better “mouse trap”.

About 15 years ago, the mill started using a small automatic battery-powered four-ounce automatic lube device that was originally used in areas unsafe for a lubricator to enter while the equipment was in operation. These performed well and failures were practically nonexistent. Why not put these on driveshafts? This would not require using four people every eight weeks per machine to grease.

Carver Machine Works, in Washington, North Carolina, worked with us to devise a workable unit for testing. We now have a true eight-point lubrication system that delivers grease on a timely basis for up to a year.

It is balanced to 0.01 inches per second (IPS) at 540 rpm. At 705 rpm it is 0.02 IPS - this is G1 specification! Delivering small precise amounts of lubricant is greatly superior to flooding the joint every eight weeks. The grease delivery for each joint is traceable; the amount of grease is easy to see through the clear bowl as the plunger travels to the bottom.

It is an excellent way to monitor the amount of grease going to each trunnion bearing. If one of the plungers stops moving, that particular trunnion bearing may not be receiving lubricant. This is a clear sign to remove that shaft and repair the problem before it causes downtime.

The True Lube System is constructed of aluminum approximately 16 inches in diameter, designed to hold eight lubricators, one for each trunnion bearing on the two crosses. It is self-contained, has its own power source and can run for up to a year. Lubricant is dispersed from the units either through stainless-steel tubing or plastic line, depending on the application. It can also be installed in less than an hour. Guard modification, if necessary, requires more time.

If the cross is drilled for center lubrication, this allows grease to flow in from the top cap and progress to the other three bearings in the cross. Although we’ve never had a failure on the self-contained units, this would be a way to get grease to all four bearings in the event a failure did occur.

We started testing the units in January 2003 on our three-ply machine. The first design used two four-packs. One pack was placed inside of the dryer next to the steam joint and the second was placed near the gearbox so it would grease all eight trunnion bearings. The heat near the steam joint melted the grease bowls. Although the bowl melted, the driver in the unit was still operable.

A further testimony to the reliability of these little auto lubers! A revised True Luber with all eight auto lubers in one pack was designed and located at the gear box end. Tubing with flexible stainless-steel hoses was used to convey the grease to the hot end of the shaft. This one performed flawlessly for the six months we’d set the autolubers to dispense their lubricant. In that six-month period, we had grease exiting the trunnion bearing seals at all eight bearings, so much so that we have now moved the cycle out to a year.

The True Luber can also be configured to lubricate gear or grid-type couplings and use oil if required.

We achieved our second goal of freeing up more craftspeople to perform other maintenance duties during a machine outage.

In conclusion, the True Luber has improved the reliability of the mill’s driveshafts and at the same time, reduced the number of people required to accomplish thorough lubrication of the machines.

Editor’s Note
This article was originally presented at the Pulp and Paper Reliability and Maintenance Conference in Atlanta, Georgia, October 2003.