The Design and Specification of a High Speed Journal Bearing Test Rig
A test rig design was developed that would enable testing of journal bearings at equivalent peripheral speeds and unit loadings comparable to those found in large gas turbine applications. The design criteria of the rig required it to attain speeds of over 16,500 sfm and impose loads of over 10,000 pounds.
The test rig rotor is driven by a 100 HP two pole induction motor that is controlled by an adjustable frequency inverter. A special carbon fiber cogged belt is used on a set of pulleys having a radius ratio of 3.54 to 1.
A light weight high speed coupling is used between the high speed spindle and the test rig rotor. The motor drives a high speed spindle that is supported on angular contact bearings. A rolling element bearing is also used on the input end of the test shaft to minimize the horsepower absorbed by the test rotor. The input end angular contact bearing is supported inside a squeeze film damper to ensure smooth rotor dynamic performance throughout the entire operating range.
The test end of the system uses a cast housing that accepts a 6 inch diameter journal bearing. The test rig shaft extends beyond the bearing housing where a duplex pair of angular contact bearings are installed on the shaft. These bearing fit into a housing that is free to rotate and move in all directions about 0.005 inches. The housing for the angular contact bearings is fitted with a hydraulic cylinder so that a downward force can be applied to the outboard bearing housing during the rotor operation. The test rig uses three separate oil systems so that the oil lubrication to the test bearing is not shared in any way with the shaft system lube systems.
The above described test rig has been built and successfully operated under full speed and full load conditions. A computerized data acquisition system measures and records the inlet, outlet and various other lube system temperatures in addition to the ambient temperature. Tests have been conducted using various oils to measure the horsepower loss associated with each lubricant. Mineral and synthetic oil have been tested using the above described test rig.
Test Rig Can Produce the Performance Map of a High Speed Journal Bearing
Wheeler Industries, Inc. has designed and built a high speed, high load journal bearing test rig that can operate a journal bearing at its actual installed application conditions. This capability enables Wheeler to validate new designs at actual operating conditions.
The test rig has been used to test the performance characteristics of various lubricants including mineral and synthetic.
Other features that have been tested include:
fixed and floating shaft seal designs
flow rates and lubricants
various configurations of tilting pad arc lengths, L/D ratios and preloads
load vs speed vs lubricant.
Smaller L/D ratio designs have been shown to be acceptable in terms of load capacity and thermal performance.
The test rig gives Wheeler the ability to compare its bearing design computer codes with the actual test results. In general, Wheeler has found about a 5% or less correlation with the predicted results.
To learn more about Wheeler Industries, Inc. bearing test capabilities contact us
Comparison Testing of Fixed and Floating Bearing Housing Seals
Wheeler Industries, Inc has utilized its fluid film bearing test rig, which is capable of running speeds of over 16,500 sfm and loads over 10,000 pounds, to study the performance of both fixed and floating journal bearing end seals. The tilting pad journal bearings were fitted with various seal designs and then tested up to full load and full speed operation. The temperature effects on the journal bearing caused by the seals was the most important parameter to be studied. Tests were conducted using various lubricants and various seal and bearing configurations.
Tests showed that the fixed end seal enabled the journal bearing to operate at a lower temperature. The fixed seal design enables the side leakage flow from the bearing to be quickly discharged and thereby reduces the churning losses in the bearing. Reduced churning losses reduces the journal bearing oil carry over and therefore the overall temperature rise in the bearing. Seal tests could be extended to study various configurations, radial clearances and oil drain sizes in order to optimize the seal configuration.
To learn more about the Wheeler Industries, Inc. Seal Test Program contact us.
What Oil Ring do I need with this motor sleeve bearing?
We recently got a call from a customer who had found the bearing he needed for a GE motor that he was repairing by searching for the GE part number – 540001. His search led him to our cross reference page where he found that the complete number was 34B540001-G01. That crossed over to our babbitt-lined sleeve bearing WS09691 SS. We had the four bearings that he needed in stock and shipped them out to him the same day.
He called back to say he also needed the oil (or slinger) rings for the bearings. Checking our records we found that we did not have that information in our inventory description. (BTW we do now!) So we went back to our print files and found that GE part number 34A770006-P02 was specified for 3.00″ shafts which matched the WS09691 SS. We sent our WR084-08 rings and our customer was back in operation.
Wheeler Industries has over 20,000 prints for motors, turbines, generators and other power generation equipment. We specialize in producing babbitt bearings, oil rings, labyrinth seals and oil deflectors for OEM’s, motor repair shops and in-house maintenance departments for nearly 100 years. Let us help you find the correct bearing by calling 843-552-1251 or visiting our website.
Why Is it Important to Choose a Fluid Film Bearing
Choosing the right bearing is essential to not only reducing operational costs but also ensuring the longevity of equipment. A fluid film bearing is a special type of bearing that allows the equipment load to be carried based on a layer of water, oil, or some other type of liquid. This type of bearing is often a popular choice for machines in which a heavy-duty bearing is required due to a long lifespan of the relevant equipment as well as a high load carrying capacity.
Fluid film bearings may also prove to be helpful in situations in which large machinery may produce intensive vibrations. Such vibrations can ultimately prove to be quite destructive to the equipment. In some instances, these types of vibrations can even result in shafts breaking, generators failing, or compressors shutting down. Over an extended period of time, excessive amounts of vibration on a piece of machinery can result in premature failure of the equipment, resulting in increased costs in order for the machinery to be replaced.
In choosing fluid film bearings, it is important to understand that there are actually many different types of fluid bearings available. The options available include Babbitt bearings. Babbitt bearings take their name from the fact that they are produced from a white metal alloy that was originally patented in 1830 by Isaac Babbitt. The primary benefit of a Babbitt bearing is that it provides a superior wetting surface that can help to decrease vibration and friction.
Along with deciding whether a Babbitt bearing is the right choice for your needs, it is also important to give consideration to the choice of material that will be used for backing the bearing. Options include bronze, cast iron, and steel. While a Babbitt bearing is relatively soft on its own, these materials can be used to provide reinforcement for the bearing. With proper reinforcement, it is possible for a Babbitt bearing to handle loads that exceed 1,000 psi.
The right fluid film bearing can provide a number of benefits while serving a variety of industries, including steel mills, construction, aerospace, nuclear, and marine industries.
Why Is Journal Bearing Design Important?
Journal bearing design can prove to be vital to the oil distribution process in a bearing. In situations in which cooling is required or contaminants need to be flushed out from the bearing, the journal bearing utilizes lubricants. The design of the bearing is vital for ensuring an effective process. Instead of greasing the part, a high speed journal bearing design relies on oil lubrication. An oil ring, collar, or a wick is typically used for supplying the oil to the bearing through the use of a pressurized system.
Grooves are typically used in the bearing’s shell in order to ensure that the oil is able to be distributed throughout the bearing’s entire surface. Proper lubrication is absolutely vital for reducing the need for journal bearing replacement.
Viscosity grade requirements are based on the oil temperature, load, and RPM of the bearing. The revolutions per minute of the shaft are most often used for measuring the speed of the bearing.
A variety of factors will often affect journal bearing design. Among these factors is compatibility, which is vital for ensuring that in the event that metal on metal friction between the journal and the bearing takes place, the two materials do not join together physically. As a result, it is possible for the lubrication system that is being utilized to withstand high seizure resistance and for the bearings to work as they are intended.
Fatigue strength is another important factor to be considered or else there is a risk of bearings becoming cracked. In the event that fatigue strength is exceeded as a result of the bearing load, the material of the bearing will often form cracks. This can often extend to the back of the bearing.
Other important factors to consider include the choice of the bearing material itself. In particular, it is vital to ensure that the material selected is capable of resisting a chemical attack as a result of corrosion resistance.
Finally, it is important to consider the ability of the bearing material to trap foreign particles, such as debris, dust, and dirt. This is a factor referred to as embeddability.
Why It is Important to Choose a Partner Who Offers Rotor Dynamic Testing
Motor reliability is essential for any facility. In certain situations, it may be necessary to take advantage of custom bearing design in order to ensure that the right parts are available for complete compatibility. Custom bearing design and modelling can provide a number of significant advantages, but it is also important to ensure that such design and modelling are backed by rotor dynamic testing.
This type of customized design can prove to be the ideal solution for meeting specific requirements as well as situations in which you require a new application to resolve an existing problem. With the assistance of a professional design and modelling team, you can rest assured that the best solution will be chosen to meet your specific needs based on a variety of configurations and materials. Rotor dynamic testing for models is vital for ensuring that the model has been thoroughly tested and refined.
Rotor dynamic testing is required to ensure that the final bearing design meets your specific needs. This type of testing is also appropriate for situations in which you may already have a prototype bearing developed and simply need to confirm that the prototype will function in the way that you desire.
Even a single design flaw can result in costly damage to expensive equipment. Such flaws can also result in significant amounts of downtime. A comprehensive analysis can provide the verification that you need prior to proceeding to production. A variety of factors will need to be considered in the design process before making the transition to rotor dynamic testing. Such factors include the type of equipment and size as well as the amount of load that the bearing will need to be capable of carrying. Additionally, the speed shaft will need to be taken into consideration along with the type of lubrication system that will be used. Other factors to be considered include the relevant application.
Rotor dynamic testing can provide a number of vital benefits in many different situations. By taking full advantage of this opportunity, you can increase equipment longevity while also reducing costs and downtime.
Advantages of Babbitt Bearings and Sound Babbitt Foundry Practices
Originally invented in the early 19th century, Babbitt metal has since come to be associated with the softest type of metal bearing material. The type of Babbitt foundry work produced today is not quite the same type of metal originally produced by Isaac Babbitt, as those formulations were kept as trade secrets. Today babbitt metals are classified by ASTM International and are divided into two main categories. First is tin babbitts whose most common alloy is ASTM B23, Grade 2. The second category is lead babbitt alloys, most popularly used being ASTM B23, Grade 7. The former is used most often because of the restrictions on the use of lead.
The selection of journal and thrust bearing materials is based on five principal factors – (1) compatibility, (2) embeddability and conformability, (3) corrosion resistance, (4) compressive and fatigue strength and (5) cost and availability. Compared to popular bronze bearings, aluminum bearings and zinc alloy bearings, babbitt bearings outperforms these other bearing materials in the first three factors. Combining a thin layer of babbitt on a steel backing markedly improves its fatigue resistance and load carrying capacity. Although more labor intense, the addition of the low cost backing reduces the overall bearing cost, making the babbitt bearing a top performer in all the desirable bearing traits.
When compared to ball and roller bearings the most significant advantages of Babbitt bearings are the gradual and predictable wear they offer. While rolling element bearings are commonly associated with catastrophic failure that is not the case with Babbitt bearings. For this reason, Babbitt-lined bearings are commonly used in high-speed compressors, large motors, generators, turbines, and internal combustion engines.
Wheeler Industries follows strict babbitt foundry procedures using centrifugal casting methods to insure high strength bonds between the babbitted bearing surface and the hard backing material. Following practices prescribed in DOD-STD-2183 and MIL-STD-271F, our ultrasonic testing of the bearing surfaces confirms the integrity of the metallurgical bond between the lining and backing. At Wheeling Industries, we are able to manufacture a wide array of designs. With almost a century of experience, we can help with the design, testing and manufacturing of almost any type of bearing.
Accuracy Matters for Precision Machining in All Industries
Much of the most precise metalworking machinery uses fluid film journal bearings. High-speed grinders are prominent in this category of machinery. Fluid film bearings are a popular choice for such machinery, as they require a heavy-duty bearing due to their long lifespan and high load-carrying capacity. Additionally, fluid bearings are beneficial in mitigating the vibrations such large machinery often produces. This type of vibration can ultimately cause tremendous damage in machinery, including broken shafts, failed generators, and shut-down compressors.
Over an extended period of time, large amounts of vibration can cause equipment to fail prematurely, and result in expensive repairs.
The most accurate grinders use lobed or tilting pad journal bearings to precisely locate the shaft in the center of the bearing and bearing housing. These designs are selected for their ability to spread the load over multiple pressure points. In a conventional cylindrical journal bearing, the load is supported by one oil wedge and reaches equilibrium at a location concentric to the center of the bearing bore. However, multi-lobe and tilting pad bearings have multiple oil wedges that share the load and increase the oil film thickness on each of the pressure points.
The higher oil flow and lighter loads allow Wheeler bearing designers to reduce the radial clearance of multi-lobe and tilting pad bearings. This reduced clearance again results in closer centerline positioning of the shaft.
These hybrid bearing designs adjust to varying loads with less centerline displacement. Loads change as the tools engage the workpiece. The damping characteristics of all fluid film bearings smoothly move to a new equilibrium position base on the altered load and speed. With hybrid designs, the increased load is spread across multiple points, and the resulting shift in position is typically less than 0.0002 inches. Machine tools using precision ball bearings experience some deflection in this scenario and, more importantly, reduced bearing life. In high-speed machinery, this condition often leads machine designers to select fluid film bearings. The result is far greater accuracy and increased longevity of equipment.
Engineers at Wheeler can design and optimize journal and thrust bearing configurations that produce lower operating temperatures, less horsepower losses, or higher load-carrying capacity.