The main reason to use a spring would be to overcome the limitations of the primary seal element.
Generally, seals made from elastomer and most polymers can energize themselves at least for a short time under certain conditions. However, as application parameters broaden, spring energizers are needed to provide consistent loading.
There are four types of springs commonly used in the industry:
1. Garter Springs
2. Cantilever or V Springs
3. Helical-Wound Springs
4. Canted-Coil Springs
The garter spring is constructed of a thin wire that is coiled and back-wound on itself, which resists stretching or being pulled apart. They are most commonly used on a radial shaft seal and helps the lip engage the shaft. There are many different combinations of wire and coil diameter, which allows us to select predictable loading across a wide range of seal diameters.
They are a good option when we have high runout in our shaft allowing the shaft seal to maintain contact with the shaft and unlike the rest of the seals we’ll talk about today. Garter springs do not require an opposing surface to push against.
The next type of spring is the cantilever or more commonly known as the V spring. It is made up of a metal strip that is punched and formed into a “V” shape. This spring geometry allows for a wide deflection range in a predictable linear load.
The shape of the spring also concentrates the load at the front of the seal – making it a good choice for excluders or scrapers in reciprocating applications. It can also be a good choice for static applications where we have wide tolerances or misaligned glands.
These are commonly selected for static applications. But sometimes we can use them in slow or infrequent Dynamic conditions.
The small deflection range of this type of spring prevents us from using them when we have wide intolerances or misalignment.
These types of springs have a very flat load versus deflection curve – making them a great option when we do run into a large gland tolerance or a misaligned condition.
They are also good options when we run into a friction-sensitive application because as the engagement of the lip changes the amount of loading generated by the spring does not change.
Welcome to our next installment of ESP’s “Not All Seals Are Created Equal.” Today we are going to talk about a seal that’s been around for a long time, but in some cases may be one of the best-kept secrets in the utilization of rotary shaft seal applications. And that is the Parker JM Clipper® seal.
What makes the JM Clipper® seal a little unique is that when we think of radial shaft seals, oil seals, we think of a metal can on the OD with a rubber element that has been molded to it that acts as the sealing element. Sometimes it has a spring to help provide the necessary pressure on the sealing lip – the necessary load – to allow it to function properly.
With the Clipper® seal you have a composite OD that is integral with and molded with, the elastomeric sealant component – can also have a spring to it for added load. Many of the same characteristics as what the traditional metal seal would be. So very robust seal and it provides a lot of rather unique benefits and features from the normal oil seal.
Let’s take a look at a few of them.
1. As mentioned, the composite OD already provides a gasket type seal. So, it exactly does perform as a sealing element as opposed to just metal-on-metal and it does not require any type of plates or secondary components to keep it in place.
2. It’s composite so it’s not going to rust or corrode – creating contamination issues.
3. It is a one-piece molded construction for the entire size range, which makes it a little bit more robust than the normal mechanical crimping or in some cases adhesive gluing of the rubber to the outer can.
4. It eliminates a lot of the problems of thermal expansion when you have extreme heat, extreme cold, and metal-on-metal – sometimes losing some of that friction fit that is necessary for the oil seal to stay in place and perform.
5. It is much easier to install and is very user-friendly.
6. It is also able to be designed for split models as well.
If you have any questions or need more information regarding the JM Clipper seal, please contact ESP International, check out our website and learn more.