Ball Bearings Sealed or open bearings 6313 C3
Ball Bearings Sealed or open bearings 6313 C3
(OP)
I ordered 6313 C3 bearings (open ones) for our electric motor.
The motor is vertically mounted and drives an hydraulic pump. The motor runs 24/7 but on very low loads.
Our dear purchase department has supplied us with the 2Z verison, i.e shielded or "sealed" otherwise same specs.
My questions are: Are they suitable to use as they are for our type of running conditions?
Can the shields be removed and used as "open" and greased as usual (albeit a risk of metal particles entering the bearing)?
Do we need to send them back and change them for opened type?
The motor is vertically mounted and drives an hydraulic pump. The motor runs 24/7 but on very low loads.
Our dear purchase department has supplied us with the 2Z verison, i.e shielded or "sealed" otherwise same specs.
My questions are: Are they suitable to use as they are for our type of running conditions?
Can the shields be removed and used as "open" and greased as usual (albeit a risk of metal particles entering the bearing)?
Do we need to send them back and change them for opened type?





RE: Ball Bearings Sealed or open bearings 6313 C3
RE: Ball Bearings Sealed or open bearings 6313 C3
Thanks for your input.
The shields are not rubber, they are metal.
The RPM on this motor is 1775 or 1800.
That, I suppose is "normal" and not considered very high speed.
At what speed are these 2Z bearings not suitable?
RE: Ball Bearings Sealed or open bearings 6313 C3
Based on our experience, I would suggest the following: Remove one shield. Hand pack the bearing with grease. Hand pack the grease cavity on the upper side of the bearing about 1/3 full of grease. Install a grease fitting and vent fitting in the same upper cavity. Leave the lower cavity below the bearing empty with no grease fittings. Install the bearing with the shield on the upper side (toward the grease). Add grease to the motor as specified by the manufacturer. Apply only the amount that they specify. Do not attempt to purge out the old grease. Do not add grease until you see fresh grease at the vent. In our plant, we would add 0.6 ounces of grease to that bearing housing every 9 months.
The shield will serve to limit the introduction of oil to the bearing. The bearing will wick in as much oil from the store of grease as it needs. If the bearing has too much grease, it can expel the excess from the open side on the bottom. I have heard it from experts and I believe it; many more motor bearings fail from over-lubrication than fail from under-lubrication.
Johnny Pellin
RE: Ball Bearings Sealed or open bearings 6313 C3
RE: Ball Bearings Sealed or open bearings 6313 C3
"2Z verison, i.e shielded or "sealed""
Shielded and sealed are not the same. For SKF, 2Z means double shielded.
You may get 100 different answers from 100 different people and there are many application/situational factors that could be considered.
As a a very conservative approximation (recommended by some bearing manfacturers), the life of non-relubricatable bearing is about twice the relubrication interval. The relubrication interval gets shorter as run-time increases (24-7 worst case), but also as size and speed (D*N) go up.
If you were at 3600rpm, I would definitely lean towards removing one or both shields since high D*N bearings.... if you left it double shielded and didn't relubricate, would expect to start seeing beairng symptoms in vibration in 2 or 3 years.
At 1800 rpm, since you've already got the shields in there, it's a tougher call, I would lean towards leaving them both in there. You will most likely have a long life of the bearings 5-10 years.
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RE: Ball Bearings Sealed or open bearings 6313 C3
Johnny Pellin
RE: Ball Bearings Sealed or open bearings 6313 C3
Our motors has no thrust bearings but two 6313 C3 bearings, I agree this sounds strange but they have all ran like that for 5 years without any problems, even though they are vertically mounted.
First: Is there an recognized procedure for the method of removing one of the shields (towards the grease)? I could use something in writing to make a procedure at my company, as this is news to me. I had no idea grease would penetrate the shield.
Second: How is the calculation done? D*n (mm x rev/ min) makes no sense to me; I assume the answer would be in hours.
What units should be used?
RE: Ball Bearings Sealed or open bearings 6313 C3
Since you have been using an open bearing with success I would not change a thing and just remove both shields. Wash out any grease inside the bearing to avoid any grease compatibility issues with what you are already using.
Remove the shields with a small screwdriver of dental pick working the shield up around the inner ring in about 6 to 8 places. Avoid scratching the inner ring.
RE: Ball Bearings Sealed or open bearings 6313 C3
I have never seen a procedure for removal of the shield. I have done it myself using a process very much like the one described by Fugeguy. I simply pried up on the inside edge of the shield until I could get a grip on it with a pair of vice-grips and then pulled it off.
Fugeguy brings up another very good point. Since your bearing came with shields, it would have been pre-greased. If you don't know exactly what grease was used, you should remove it. The thickeners in grease are very often incompatible. If you added a Lithium based grease to the pre-charge of Polyurea based grease, the thickeners would have an adverse reaction with undesirable properties. Most motor manufacturers supply their motors with Polyurea based grease. But, bearing suppliers selling bearings for an unknown application may use something else.
To restate my recommendation one more time, I would install the bearing with a shield toward the grease and the opposite shield removed. As I noted above, this was confirmed with our alliance partners. At the time, those included Siemens motors, SKF bearings and Exxon-Mobil lubricants.
But, removal of both shields would not pose a problem as long as your operators do not over-grease (too often or too much).
Johnny Pellin
RE: Ball Bearings Sealed or open bearings 6313 C3
In principle there is nothing wrong with leaving a shield on the bearing.
It is not a panacea for over greasing. I've seen several over greased bearings that grease pressure (a grease gun can generate thousands of psi) actually collapsed the shield into the bearings.
RE: Ball Bearings Sealed or open bearings 6313 C3
Your motor's lower (axial load carrying) 6313 Z single row, deep groove ball bearing should have an L10>1x10^6 hours assuming:
-grease lubrication
-normal cleanliness
-1800 rpm
-axial load <150 lbf
-150degF max operating temp
Also, regular applications of grease serves a very important function with regards to bearing life. The new, clean grease should displace the old grease which is likely contaminated with debris and moisture. Debris and moisture are the most common causes of rolling element bearing failures.
Regards,
Terry
RE: Ball Bearings Sealed or open bearings 6313 C3
PS Distributors rarely stock open bearings, as the shielded type will fit more varieties, they can always pull shields off, but you can't add them.
Russell Giuliano