K-Cartridge™ Cement Pump Seal Assembly

Figure 1 — This shows the K-Cartridge cement pump seal assembly installed on a pump.
Figure 1 — This shows the K-Cartridge cement pump seal assembly installed on a pump.

Introduction to the K-Cartridge

The K-Cartridge-brand cement pump seal assembly (Figure 1) uses hydrodynamic seals to address the extreme challenges faced by the mixing and charging pumps of oilfield well-cementing trucks.  The cartridge replaces the removable stuffing box on 4 x 5 and 5 x 6 Twentieth Century and Gardner-Denver brand centrifugal pumps. We tested the K-Cartridge with a sand slurry for over 500 hours in the lab and have been selling them to the field since 2005.

As with conventional stuffing-box mounted cement pump seal arrangements, the K-Cartridge is supplied with a pressurized lubricant at   ̴60 psi by a conventional air-over-oil lubricator. One lubricator per pump is recommended.

A cross-section of the K-Cartridge is included as Figure 2. Two hydrodynamic cement pump seals contain the pressurized lubricant and two lip-type barrier seals face and contain the cement. One hydrodynamic seal prevents lubricant loss to atmosphere. The other serves as a miniature rotation-driven pump to pressurize, lubricate, and flush the lip seals. All seals run on a hard-coated pump shaft to minimize wear.

A shaft driven fan provides forced air cooling of the cement pump seal assembly. Heat transfer is further augmented by the shape of the housing and its ample contact with the cement-cooled casing of the pump, and by heat draw from the shaft to the cement-immersed impeller of the pump.

Figure 2 — In the K-Cartridge-brand cement pump seal assembly, a Filled Seal prevents loss of the pressurized seal lubricant to atmosphere. The rotationally driven pumping action of a High Film Seal produces a controlled flow that pressurizes, flushes, and lubricates a pair of lip-type barrier seals that face and contain the cement. The rotating fan helps to dissipate speed-related seal-generated heat.
Figure 2 — In the K-Cartridge-brand cement pump seal assembly, a Filled Seal prevents loss of the pressurized seal lubricant to atmosphere. The rotationally driven pumping action of a High Film Seal produces a controlled flow that pressurizes, flushes, and lubricates a pair of lip-type barrier seals that face and contain the cement. The rotating fan helps to dissipate speed-related seal-generated heat.

The hydrodynamic cement pump seals

The hydrodynamic cement pump seals that contain the pressurized lubricant are a High Film Kalsi Seal and a Filled Kalsi Seal. Both seals are installed in housing grooves, compressed radially against the pump shaft, and seal statically like other interference-type seals. The dynamic lips of both seals have hydrodynamic waves. When the pump shaft rotates, the seals remain stationary and the sealing interfaces between the seals and the shaft become dynamic. During shaft rotation the hydrodynamic waves force a film of lubricant across the dynamic sealing interfaces. The seals hydroplane on the film as long as shaft rotation continues. This hydroplaning action reduces seal friction, wear, and seal generated heat, prolonging seal life at the relatively high speeds of cement pumps.  Both hydrodynamic seals provide a liquid-tight seal in the absence of rotation.

The Filled Kalsi Seal (Figure 3) is located at the air side of the cement pump seal cartridge and prevents the loss of the seal lubricant to atmosphere. It has an annular groove that is filled with a soft energizing material. The construction method reduces the radial cross-sectional tolerance, compared to seals with mechanically retained energizers. This composite construction produces a light lip load that further reduces seal-generated heat – an important attribute at the high rotary speeds of cement pumps. The hydrodynamic waves of the Filled Seal are selected to produce low hydrodynamic pumping related lubricant leakage.

The waves on the High Film cement pump seal (Figure 4) have an aggressive design that causes them to have a significant hydrodynamic pumping rate during shaft rotation – a pump rate that provides a metered flushing rate without the need for a troublesome needle valve. The seal acts as a miniature pump to pressurize, lubricate, and flush a pair of more conventional lip type cement pump seals that face the cement-filled volute of the pump. The High Film Seal also provides redundancy to the lip seals, in terms of containing the cement slurry.

Figure 3 — The air-side cement pump seal is a Filled Seal. It has hydrodynamic waves that lubricate its dynamic interface with the rotating pump shaft, reducing friction and seal generated heat. A soft energizer reduces lip load against the pump shaft, further reducing friction and heat.
Figure 3 — The air-side cement pump seal is a Filled Seal. It has hydrodynamic waves that lubricate its dynamic interface with the rotating pump shaft, reducing friction and seal generated heat. A soft energizer reduces lip load against the pump shaft, further reducing friction and heat.
Figure 4 — In the cement pump seal assembly, the pumping action of the High Film Seal is used to pressurize, flush, and lubricate a pair of lip seals that face the cement slurry. The pumping action is produced by the waves on one side of the dynamic lip. The other side of the lip has an abrupt circular edge for abrasive exclusion.
Figure 4 — In the cement pump seal assembly, the pumping action of the High Film Seal is used to pressurize, flush, and lubricate a pair of lip seals that face the cement slurry. The pumping action is produced by the waves on one side of the dynamic lip. The other side of the lip has an abrupt circular edge for abrasive exclusion.

Kalsi Engineering Company Background

The main offices of Kalsi Engineering are in Sugar Land, Texas, which is part of the Houston metropolitan area. We have been serving the oil and gas industry since 1978 with consulting engineering services and rotary shaft seal technology. Company founder M. S. Kalsi, PhD, P.E. became interested in rotary sealing while pursuing his masters and doctorate degrees. His fundamental research produced the lubrication concept used by our cement pump seals. Our commitment to continuing research has produced a variety of advanced rotary shaft seal products with extended performance envelopes. Contact us to discuss your rotary shaft seal requirements.

Call us today at 281-240-6500 to discuss how our innovative cement pump seal cartridge can reduce the cost and inconvenience of your pump maintenance.
Call us today at 281-240-6500 to discuss how our innovative cement pump seal cartridge can reduce the cost and inconvenience of your pump maintenance.