Alb Mod Bearing Seals and Pillow Blocks Flashcards
There are two basic ways to seal a bearing. One way is to install a seal on the bearing housing. This would be described as a:
External seal
An external seal has the advantage of offering a wide selection of:
Materials and styles
There are two basic ways to seal a bearing. One way is to install a seal on the bearing itself. This would be described as a:
Integral seal
An integral seal has the advantage of being
Cheaper and more compact
Rubbing seals are also called:
Contact seals
Non rubbing seals are also called:
non-contact seals
Since rubbing seals contact the sealing surface, they have two main advantages over non rubbing seals. What are they? (2)
- Can retain grease as well as oil
- Provide a positive seal against moisture and fine contamination
Why does a rubbing seal have a lower speed limit?
The friction generated by the seal rubbing on the sealing surface limits speed
The ___ seal makes a seal by pressing the seal lip against the seal surface.
lip
With a lip seal, the light contact pressure before start up is provided by: (2)
- Garter spring
- Light interference fit between seal and shaft
With a lip seal, the contact pressure may be increased after start up by: (2)
- Whirling lubricant presses on inside of lip
- Gas or liquid pressure presses on inside of lip
The surface speed of a lip seal on an unhardened shaft is limited to:
4 Meters/second (13.12 ft/second)
Using a hardened shaft with a lip seal can ____ your speed limitations vs an unhardened shaft. Requires a hardness of rockwell C45 and a surface roughness of ___ microns
double
0.8 microns
The temperature range on a lip seal is limited to ___ C to ____ C
-40C to 200C
What are four notes you should keep in mind regarding the lip seals? (4)
- Requires film of liquid to form seal
- Requires finish free of burrs and scratches
- Requires any marks from machining or polishing to be perpendicular to the shaft axis
- Requires no contamination between lip and shaft
A lip seal is damaged easily upon installation. If damaged, it:
Fails very quickly
When installing a lip seal, ensure the bore is:
Clean, free of burrs and deposits
When polishing a lip seal surface on a shaft, avoid ____ and ____ scratches
Spiral and longitudinal
Note: they provide a leak path through the seal
You should install this on a shaft before installing the shaft in a lip seal. Helps prevent the lip from being damaged by the shaft shoulder
Thimble
This seal acts as a contact seal up to a surface speed of 12 meters/second. Above that, it requires a steel support ring.
V-ring seal
With a V ring seal, above ___ Meters/second the lip of the seal lifts off the seal surface, at this point the only sealing action is from a flinging effect.
15 M/s (49.2 F/s)
This seal can be used with grease or oil. It is fitted tightly to the shaft and exerts a light axial pressure against a smooth surface on the housing. Can tolerate a large amount of axial misalignment at low speeds.
V-ring seal
When mounted outside the housing, it can only retain grease and not oil
___ seals are very simple, and the cheapest seal. Mainly used for grease, they are classified as a low speed seal and don’t handle chemicals or temperatures over 100C.
Felt seals
Note: should be soaked in oil before installation to reduce friction and wear
This type of seal can handle low peripheral speeds, severe service conditions, wet and dirty environments and provides a leakproof retention of lubricants.
mechanical seal
Note: most expensive bearing seal.
this seal can keep out vapors and liquids, but is better for lower surface speeds. Are part of a bearing assembly
Integral rubbing seals
Because non rubbing seals have no contact with the sealing surface, they offer these advantages: (5)
- No rubbing friction
- No wear
- Not as easily damaged
- No speed limits
- Can run at higher temperatures
Note: Adding grease into the gaps can further increase the sealing efficiency
The main disadvantage of non-contact seals is they do not provide a _______ and cannot retain oil, only grease
positive seal
Non-contact seals do not provide a positive seal, and cannot contain oil unless one of these two implements are used: (2)
- Spiral groove
- Flinger
The effectiveness of all non-contact seal arrangements depends on the: (2)
- Narrowness of the gaps
- Number of gaps
Note: seal is better with more, smaller gaps
External non-rubbing seals are mounted on the:
Housing
This non-rubbing rubbing seal is the simplest and cheapest of the non-rubbing seals. Has a smooth gap at at the surface of the shaft, and is only effective in a dry, dust free environment for grease lubricated bearings.
Smooth Gap Seal
This type of non-rubbing seal is used in split housings, and can only tolerate limited axial or radial shaft movements.
Radial Labyrinth seals
This type of non-rubbing seal can be used in a one piece housing. Axial movement does not alter the widths of gaps, which allows the gaps to be made very small
Axial labyrinth seal
This non-rubbing seal is more effective than using a radial or axial labyrinth seal.
Combination axial radial seal
This non-rubbing seal uses pressed steel washers to provide the cheapest labyrinth seal.
Sealing washer set
With a sealing washer set, the efficiency of the seal can be increased by:
Increasing the number of washer sets
With sealing washer sets, ________ attached to the shaft acts as a deflector and increases the efficiency of the seal
rotating discs
______ are attached to the shaft and rotate within a groove in the seal, returning oil to the housing.
Flinger rings
Note: oil returned via a return duct
Flingers extend the use of the _____ seal to oil lubricated bearings
Labyrinth seal
Integral non-rubbing seals are commonly referred to as _____
shields
Does not restrict max operating speed, is most commonly used on small bearings
Shields consist of a thin metal cover that is attached to the outer ring of the bearing, but:
does not quite touch the inner ring
This type of seal is factory pre lubed with grease, and cannot keep out liquids or vapors.
Shield or integral non rubbing seal
If there is substantial radial loading 55-120° perpendicular from the shafts axial center, ____ should be installed to ensure the pillow block is not pulled out of alignment
stops
Should also be installed if there is substantial axial loading
If the load is not vertically down from the shafts axial center, the capacity depends on the strength of the cap and whether ____ or ____ are used.
two or four cap bolts
The load capacity of a horizontally split pillow block bearing is reduced by ____ to _____ at 55° as the angle increases or if the loading is axial
one third to two thirds
Horizontally split Pillow block bearings are intended mainly for _____ loads
radial
The load capacity of a radial, straight down load on a horizontally split pillow block bearing is:
the same as the bearing capacity
The bearings most commonly housed in an anti friction pillow block bearing are: (2)
- double row spherical roller
- double row self aligning ball
On a horizontally spilt pillow block bearing, the cap is removeable to: (2)
- assist in installation
- assist in lubrication
A horizontally split pillow block bearing has dowel pins, which:
help with properly aligning the cap
Horizontally split pillow block bearings housings have what two features which allow a bearing to float? (2)
- clearance in the bearing seat
- extra room axially for movement
What is used to hold a bearing in position axially in a horizontally split pillow block bearing?
locating ring
If using only one locating ring, what side should the ring go on?
The side with the locknut
What is the cheapest, but also weakest of the materials available for a pillow block bearing?
Cast iron
Ductile iron has a higher load rating than a cast iron pillow block bearing, but ____ is normally used in the most severe service where there is heavy shock loading
cast steel
Can you interchange the cap from one pillow block to another?
No, they are made in matched sets
The cap bolts on a pillow block bearing must have ____ to remain tight through the cycles of loading and unloading
sufficient pre load
The rule of thumb for grease fill on a pillow block is to fill _________ of the free space around the bearing.
one third to two thirds
Exception is made for so called “total fill” greases such as lithium soap water resistant grease which can be filled to 90%
The important thing to remember when greasing a pillow block bearing is:
There should be enough free space for the grease to circulate and not cause heat build up
For re-lubrication, the grease fitting should be located on the side of the cap:
opposite the retaining nut.
Note: this is to avoid having the grease fibers torn as the grease is injected over the notches in the retaining nut
Locating rings can also be called:
stabilizing rings or fixing rings
A bearing that is allowed to float axially could be called:
a free or a floating bearing
It is important to have floating bearings to allow:
axial expansion of the shaft
While floating bearings are important, it is also usually necessary to have one:
Fixed bearing
What do you use to create a fixed bearing in a pillow block?
locating ring(s)
Where do you normally have the fixed bearing located?
Drive end of the shaft
Different models of pillow blocks are made to accept _____ seals
Any external seals
What determines the type of seal that can be fitted to a pillow block? (2)
- Diameter of the opening around the shaft
- groove dimensions in the housing
A grease fitting is included with some labyrinth seals to allow the grooves to be filled with grease, which gives you:
a more efficient seal
When greasing a bearing and a seal, the procedure is to grease what first?
Bearing first, then seal
This type of pillow block is constructed in one piece, and it’s load capacity is not reduced by angular loads. Bearings can be swapped quickly and easily, while also being self aligning. The housing itself is cheap.
Unit pillow blocks
With unit pillow block bearing inserts, an interference fit bearing can be operated at full load capacity. However, with the eccentric locking collar or set screws on a slip fit bearing, the load capacity is:
reduced
Those two methods force the shaft slightly off center resulting in vibration
A flanged bearing housing has its base at ___ ° to the axis of the insert
90°
What metallic bearing materials can be used in a plain pillow block bearing? (3)
- Babbitt
- Aluminum
- Phosphorous bronze
What non-metallic bearing materials can be used in a plain pillow block bearing? (3)
- Nylon
- Teflon
- Phenol Laminates
Other pillow block joint designs can increase the angular load capacity. These designs include: (4) and which is the strongest for side loads?
- Angle
- V
- Gib (strongest for side loads)
- Solid plain
What is the disadvantage of a solid plain bearing pillow block?
Must be either installed on the end of a shaft, or needs components removed to slide onto the shaft.
