Hydrodynamic lubricating action

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Designed for severe service conditions

Simple One Piece Design

How are Kalsi SealsĀ® used for high pressure?

Introduction

There are four basic categories of Kalsi-brand rotary seals that are used for retaining high differential pressure. Each of these seal categories requires a different hardware implementation. The first seal category is the broadest and includes many of our solid cross-section direct compression seals, such as our Wide Footprint, Hybrid, Enhanced Lubrication, and Plastic Lined seals. The second and third categories are lip seals: our KLS® seals and washpipe packing. The fourth category is our BDRP seals™.

Category 1: Solid cross-section seals with waves on the pressurized lubricant side

Most Kalsi-brand rotary seals that are used for retaining high differential pressure have a solid cross-section, are designed to retain a pressurized lubricant, and have hydrodynamic waves that face the pressurized lubricant. These waves pump lubricant into the dynamic sealing interface when the shaft rotates. When this type of rotary seal is used to retain a pressurized process fluid that is not a lubricant, a pair of oppositely facing seals is used, and lubricant is provided between them that is pressurized to a value equal to or greater than the pressure of the process fluid. With this type of arrangement, one rotary seal serves as a partition between the process fluid and the seal lubricant, and the other retains the lubricant pressure. Both rotary seals are mounted in housing grooves and compressed radially against the rotatable shaft. The system that provides the pressurized lubricant also accommodates the hydrodynamic pumping related leakage of the Kalsi Seals.

The point of any high pressure rotary seal is to prevent fluid loss through the clearance gap that exists between a machine housing and a shaft. The smaller the clearance gap, and the less it changes due to factors such as shaft runout and deflection and housing pressure breathing, the better the seal can withstand high differential pressure – provided the shaft doesn’t rub on the housing and generate enough heat to damage the seal. Because of the critical nature of the clearance gap, special hardware has been developed that allows the gap to be optimized, including laterally floating metal backup rings and laterally floating seal carriers. If desired, capacity can be further increased by pressure staging.

The ultimate pressure capacity of a Kalsi-brand rotary seal depends on several factors, such as the type of seal carrier and the clearance gap size that are used, the seal material, the rotary speed, the aggressiveness of the hydrodynamic waves, the ambient temperature, the degree of available heat transfer, and the required seal life. As an example of the results that can be achieved, we tested 2.75" (69.85mm) plastic lined Kalsi Seals at 7,500 to 7,800 psi (51.71 to 53.78 MPa) and  252 feet per minute (1.28 m/s) for 1,000 hours. The seals were still in excellent condition at the end of the test. The ISO 150 viscosity grade seal lubricant was maintained at 130°F (54.44°C) by a small amount of fluid circulation inside the hollow shaft.

Category 1 Kalsi Seals are available in a variety of materials and high-pressure shaft seal designs. Seals with plastic-lined construction have the most pressure capacity, followed by seals with dual durometer construction. For a complete list of all our seal material options, visit our materials web page. Our rotary seal handbook provides more information on the various seal materials and geometries we offer, and provides detailed information about implementing Kalsi seals in rotating machinery.

Category 2: KLS high pressure lip seals

KLS seals are spring-loaded lip seals that have hydrodynamic waves at the low-pressure end of the seal. The spring end of the seal faces a pressurized process fluid and is supported by a housing wall. The wave end of the seal faces an unpressurized lubricant, such as the bearing lubricant of a machine assembly. If the process fluid contains abrasives, a pair of KLS seals are used, and a barrier lubricant is provided between them that is balanced to the pressure of the process fluid. With this arrangement, the inboard KLS retains the differential pressure and lubricates and flushes the outboard KLS. KLS seals were originally designed as oilfield RCD seals, and chapter E6 of our rotary shaft seal handbook details how to implement KLS seals in an RCD.

Category 3: Kalsi Washpipe packing

Kalsi Washpipe packing is interchangeable with the conventional packing that is used in the washpipe assemblies of oilfield power swivels and top drives. Like conventional packing, it is supported by and clamped between form-fitting metal spacers. Kalsi packing incorporates hydrodynamic waves on the low-pressure end of the dynamic sealing lip. Lubricant is provided to these waves by the conventional re-greasing operation. We provide hardware-related guidance to organizations that use our packing to help them obtain maximum performance.

Category 4: BDRP-brand rotary seals

BDRP-brand rotary seals have an elastomer body with a plastic lining that incorporates aggressive hydrodynamic waves. BDRP seals are designed to serve as hydraulic swivel seals and can seal lubricant pressure in either axial direction. They are simply installed in a housing groove and compressed radially against a rotatable shaft. Pairs of adjacent seals are used to define hydraulic channels between the housing and the shaft.