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Seal Wave Design Lubricates Interface

Suitable for transient conditions

What are the requirements of a high performance rotary seal?

Rotary seals exist in a bewildering variety of designs for a very good reason. In the universe of rotary sealing applications, operating conditions vary by an astonishing degree, and highly engineered solutions have been developed that are tailored to specific sets of conditions. No single “best” seal design exists that is appropriate for all applications. For example, the garter spring energized lip seals that work extremely well in automotive axles would be a disaster in a hydraulic swivel, or an oilfield rotating control device, or a sealed bearing mud motor. The same is true of the face seals that run flawlessly in automotive and swimming pool water pumps for thousands of hours. Each application has its own severe challenges, and the very features that provide high performance in some applications lead to rapid failure in others.

Like all rotary seals, Kalsi Seals are designed for specific operating conditions. In general, Kalsi Seals are used to seal moderate to extreme differential pressure, and are often simultaneously used to partition an abrasive environment from a bearing lubricant. Within this general category of operating conditions, specific seal designs have been developed for specific conditions. One commonality between all Kalsi Seals is the use of highly engineered hydrodynamic inlet features that utilize shaft rotation to pump a thin film of lubricant into the dynamic sealing interface between the seal and the shaft. This lubricating film minimizes adhesive wear, reduces seal generated heat, and allows a wide dynamic lip to be used. The robust dynamic lip width provides strength that helps the seal to withstand high differential pressure, and also provides sacrificial material to accommodate axially acting seal wear that can occur due to factors such as third body wear and high pressure extrusion damage.

In terms of sealing differential pressure, Kalsi-brand rotary seals can be divided into three categories: Seals for low and potentially reversing levels of differential pressure, seals for low to extreme (up to 7,500 psi) differential pressure acting from the lubricant side, and seals for moderate (up to 1,000 psi) differential pressure acting from the environment side. A few examples of Kalsi Seals with high performance features that are tailored for specific operating conditions are provided below.

Axially Constrained Kalsi Seals are designed for partitioning a lubricant from an environment in conditions where the differential pressure is essentially zero, but may temporarily increase up to 50 psi in either direction. An example of a typical application is the pressure compensation piston of an oilfield sealed bearing mud motor. The features that allow such service are a specially designed seal body that contacts both groove walls, and an environment side chamfer that increases interfacial contact pressure on the environment side of the seal. Several other types of Kalsi Seals can also be used for this type of service if axially spring loaded.

Wide Footprint Kalsi Seals are designed for partitioning a lubricant from an environment in conditions where the pressure of the lubricant is significantly higher than the pressure of the environment, and lubricant consumption by the seal must be minimal. The wider dynamic lip of these seals helps them provide longer life in applications such as the fixed location seal of a sealed bearing mud motor.

Hybrid and Enhanced Lubrication Kalsi Seals are designed for lubricant pressure retention in applications that can tolerate higher hydrodynamic pumping related leakage, or require the use of low viscosity lubricants. When used with dual durometer or plastic lined construction and floating backup rings, these seals provide the highest pressure capacity of our product line. These rotary seals are especially appropriate for use in demanding high pressure applications such as hydraulic swivels and oilfield rotating control devices.

The Kalsi Seal family of rotary shaft seals is uniquely designed to excel under demanding operational and environmental conditions. Whether your need is a for a low or high pressure shaft seal, one of our patented rotary sealing solutions may provide the high performance, reliability and economic advantage your equipment needs. For information on the design and performance characteristics of other types of Kalsi Seals, visit the catalog and technical section of our rotary seal handbook. For assistance in selecting and implementing Kalsi brand rotary seals, send us a completed application questionnaire.

We ensure the consistency and quality of all of our seals through extensive inspection and testing. Our quality control procedures include our registered ISO 9001:2008 Quality Management System. Let us show you what high quality and high performance means.

What makes a Kalsi-brand rotary seal different?

Rotary seals exist in a confusing array of designs that are directed at specific operating conditions and application requirements. Kalsi Seals are primarily directed at applications that require abrasive exclusion and the ability to withstand some level of differential pressure. Kalsi brand rotary seals include both lip type and direct compression seals. Some are designed to exclude abrasives in low levels of reversing pressure. Many are designed to retain high differential pressure acting from the lubricant side of the seal, and most of these types of rotary seals are also designed to exclude abrasive environments. Others are designed to retain medium to high differential pressure acting from the side of the seal that faces the abrasive environment.

Three key features make Kalsi Seals® different from other types of rotary seals. First of all, Kalsi Seals use a relatively wide dynamic interface, to provide ample sacrificial material to accommodate third body wear and pressure related extrusion damage. The associated wider dynamic sealing lip also makes the seal inherently more extrusion resistant, by reducing pressure related stress.

Most polymeric rotary seals use a relatively narrow dynamic interface to reduce seal generated heat. The wide dynamic sealing interface of a Kalsi Seal is made possible by providing hydrodynamic inlets that force a thin film of lubricant into the interface in response to rotary motion of the shaft. This hydroplaning effect lubricates the seal and shaft, preventing the typical adhesive wear, high running friction, and heat associated with conventional non-hydrodynamic seals, As a result of the lubricated wide interface, Kalsi Seals can handle higher pressure and speed combinations than other polymeric rotary seals. For a slow motion animation of the hydrodynamic lubrication of a Kalsi Seal, click here.

The third key feature of a Kalsi Seal is a circular exclusion edge that faces the abrasive environment. In seals directed at sealing an environment pressure that is greater than the lubricant pressure, geometry features are incorporated that cause increased contact pressure at the exclusion edge, for enhanced environmental exclusion. In seals directed at sealing a lubricant pressure that is greater than the environment pressure, the contact pressure at the exclusion edge is amplified by differential pressure effects. Seals that are designed for low levels of reversing pressure also incorporate a special seal body design that allows the seal to be axially constrained by the seal housing, In other seal designs, the circularity of the exclusion edge is assured by the differential pressure acting across the seal.

Kalsi Seals that are designed for high levels of differential pressure employ composite construction that places a high modulus elastomer or plastic material at the extrusion gap clearance between the housing and the shaft. This construction allows the seals to exploit the favorable extrusion resistance characteristics of the higher modulus material without a corresponding increase in interfacial contact pressure.

Comprehensive engineering literature and one-on-one engineering support are available to help you specify and implement the most appropriate seal for the operating conditions of your equipment.

Can a rotary seal specialize in handling both high pressure and high temperature?

Kalsi Seals are polymer based rotary seals that are used to seal the clearance between a shaft and a housing. The ability of such seals to bridge high differential pressure decreases as the seal temperature increases, because the modulus of the seal material, and resistance to compression set, decrease.

The running temperature of a polymeric rotary seal depends on a number of factors, such as the environment temperature, the heat transfer response of the system, and the amount of heat generated by the seal. The amount of seal generated heat depends on factors such as the width of the dynamic sealing interface, the rotary speed, the frictional characteristics of the polymer, and the degree of seal to shaft asperity contact within the interface. The interfacial lubrication provided by the hydrodynamic features of a Kalsi Seal minimizes asperity contact within the interface, lowering seal generated heat. This allows the use of the relatively wide dynamic interface that is needed to resist differential pressure, giving Kalsi brand rotary seals an important advantage over comparable non-hydrodynamic seals.

Although the temperature and resulting modulus of the seal material are key factors that govern the pressure capacity of a rotary seal, there are other equally critical factors. Three important factors are the size of the clearance between the shaft and the housing, how much that size changes due to runout and deflection, and how frequently the size changes. The smaller the clearance, and the less it changes, the higher the pressure capability of the sealing assembly.

Because of the importance of hardware design, Kalsi Engineering publishes a rotary seal handbook that provides comprehensive coverage of hardware design practices, including information on ways to minimize the clearance between the shaft and the housing. We also offer a training course on hardware design, and have experienced staff members who can provide design guidance and feedback.

Although there are exceptions, Kalsi brand rotary seals that are intended for pressure retention service are typically made at least in part from HNBR for seal temperatures up to 300°F, and are typically made at least in part from FKM for seal temperatures up to 400°F. The actual differential pressure that such seals can withstand is largely dependent on the quality of the installation, and other factors described above. When used with favorably sized clearance between the shaft and the housing, HNBR based seals can bridge fairly high differential pressure at 300°F, and FKM can still bridge moderate differential pressure at 400°F."