Introduction to Radial Shaft Seals

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Video Transcript

Hi, I'm Lewis Lenz. I'm an application engineer here at engineered seal products. Today I would like to go over an intro to radial shaft seals. Specifically, to discuss the application details of what the customer's parameters might be, the envelope in which the seal is going to go into, and then some common lip profiles that we typically recommend.

Application Details

1. SIZE
   
   The first thing that we typically get from the customer is the size.
   
   
   • How big is your shaft?
   • How big is your bore?
   • What's the width that the seal is going to fit into?
   These are very important because our engineering design guide revolves around this.
2. TEMPERATURE
   
   We need to know:
   
   
   • What's the low temperature?
   • What's the high temperature?
   This is very important for material selection. We want to make sure we get a good material where the seal is going to be able to flex at colder temperatures. As well as on the high end - we don't run into a material that gets eaten away.
3. FLUID & DEBRIS
   
   We need to pick a material that works well with a fluid. Whether it's grease or an oil, we need to make sure that the material is compatible with the fluid.
   
   Debris - we need to know if we're trying to keep debris out of the system. This typically utilizes a dust lip on the seal, but we can get into more complex profiles based on how much debris that you think your system is going to see.
4. PRESSURE
   
   We don't like a lot of pressure in the system. We recommend about 7 PSI as a max. This is a very low-pressure seal that we recommend.
5. MOTION
   
   
   • Is the seal going to be rotating?
   • Is it going to be reciprocating?
   • Is it going to be oscillating?
   These are all parameters that we need to know, as well as the shaft speed. Shaft speed goes along with temperature. We want to know what the under lip temperature is going to be based off of how fast that shaft is rotating and the friction generated and will be important for selecting the right materials.
6. DESIGN ACTION REQUEST FORM
   
   We have a design action request form that captures all of these parameters. Feel free to reach out and we can get that form over to you.

Envelope

For the shaft, we typically recommend a Rockwell hardness of C30 where the materials are carbon steel. We recommend a 30° chamfer angle at varied lengths based off of how big the shaft size is.

For your bore, we typically recommend steel and cast irons. The reason for this is thermal expansion and we want to try to make sure that we're not going to be growing the material. The chamfer - we recommend 15° to 30° - or from 1-1/2. mm to 2.2. mm.

Common Lip Profiles

1. Oil Seal
   
   The most used common lip profile is going to be your oil seal. It's used to keep oil one side of the system that you don't want oil to leak out. It's utilizing a garter spring to help push down on the shaft.
2. Seal With Dust Lip
   
   Now let's say you have contamination that you're trying to keep out. This is where you're going to utilize a dust lip. This seal profile here can also utilize the garter spring but just for general purposes you're trying to keep contamination from entering the system and you're trying to prevent fluid from exiting the system. These are typically used more for oil. You could utilize grease in these, but because you are trying to trap oil from the inside, it is more common to go with a multi-lip seal.
3. Multi Lip Seal
   
   It's good for contamination and keeping debris out. Utilizes each lip in order to prevent anything from getting into the system.
4. Multi Lip Seal
   
   It's good for contamination and keeping debris out. Utilizes each lip in order to prevent anything from getting into the system.
5. Oil Separating Seal
   
   Typically, you have two different places where you are trying to prevent the oil from mixing. It utilizes a garter spring to keep it on each side respectively.

Each of these seals typically run on either some kind of oil film or really need to utilize lubrication. If not, you can cause the seals to burn out easily. We recommend that you don't run in a dry system. Whether that be oil or grease, we recommend some kind of lubrication.

Common Bore Types

1. Can
   
   We have your typical can that's going to go on your bore. This is to help the structure of the seal stay in place. You typically utilize OD paint on the OD to make sure that it helps with the seal-ability. Any imperfections from the steel or cast-iron is going to be covered up by the OD paint. Now if the steel or cast iron has too much OD paint, then we recommend a rubber covered seal.
2. Rubber Covered
   
   This helps utilize rubber to seal from the OD. But the biggest issue with this is spring back. And the seals might have the opportunity to push out once you install them.
3. Heel Case
   
   The heel case utilizes your rubber portion and your can portion. It helps with the structure and its utilizing the can to help with installation but then it's also utilizing the rubber portion to help with seal-ability on the OD.
4. Double Case
   
   The double case, more for bigger profiles, helps the structure of the seal stay in place.
5. Flange Style
   
   The one profile that's not on here is a shotgun [flange] style seal. It utilizing a can but it's flanged up like this, and it's to help with installation, ease of removal, and it puts the seal in place.

Like I said, this is an overview of common, lip profiles, bore profiles, and what we try to see and get from you to understand the application that you're providing. Feel free to reach out with any questions or concerns you may have and we'd be happy to go over the design action request form with you.