Bearing Selection

[manian]

Can any body provide the correct procedure for selecting Thrust Ball Bearing for Industrial Valve applications ? The information provided by Bearing Manufacturers does not cover this end use. The valve is only manually operated where the speed is low. If we select a bearing as recommended in manufacturers catalogs we end up with a big size bearing considering the life/speed etc. Is there any separate selection methodoly adopted by valve designers to make it economical ?

 

[MikeVV]

Ball bearing selection is a function of life, load and environmental factors. Most bearings are made for continous duty under load and are vastly over-designed for intermittent, light load, duty.<br>
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Are you designing this valve? Valve bearings are typically sized by the valve manufacturer. Is this a glove valve, gate valve, etc. What are the seal requirements (pressures and fluid) along the valve shaft? The bearings also must be selected with consideration for lubricants and contaminants to or from the bearing to the fluid.<br>
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I found the following valve suppliers from a supplier of mine, Rust Instrumentation, West Jordan, Utah - Timken, Schrader-Bellows, Apollo, Asahi/America, Centerline, Flexible Valve, ITT Industries - Engineered Valves, Parker and Westlock. Maybe they can help.

 

[manian]

Many thanks for the response. <br>
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Yes. i am involved in the design of this valve. The subject equipment is a 8" Cl 600 globe valve. The calculated load ratings are higher than that of the bearing selected. i.e the bearing capacity is only 80% of the calculated rating.<br>
Is it acceptable ? If not what is the correct industry practice ? It will be of immense help if some one can throw more light on this area/give a reference to where we can get this info. Sometimes, competitors/other manufacturers hesitate to provide such technical data. The bearings are totally isolated from the line pressure.

 

[MikeVV]

Are the bearing capacity parameters static side and thrust load? Are these loads defined relative to a number of cycles? Are dynamic loads also defined?<br>

 

[manian]

Only momentary loads are defined. Dynamic loads are incalculable. Number of cycles are not known since it depends on the life of the product. The only data available is the the axial thrust load of X. With this we must be able to size the bearing. From here onwards how do we proceed? Speed is too slow and the valve is only manually operated.

 

[LarryW]

Try to get an engineer from a bearing manufacturer to help you out.<br>
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We had a similar problem with tapered bearings. Are rates were very slow (0 to 2 degrees/sec). We were told that the static rating is for 0 RPM ONLY and that for spped between 0 and 5 RPM we were in no-man's land. For a 5 RPM rating they told us to multiply the 500 RPM rating by 4. They aslo stated that some of their customers use a factor of 6 because the load cases were infrequent and the movement did not occur under load. We had strict diameter constaints, so we ended with a larger bearing than needed anyway.<br>
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Bottom line is try to get good help from the bearing manufacturer.

 

[manian]

Thanks Mr Larry.<br>
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i have requested some of the bearing manufacturers. but haven't heard from them yet.