A03_Kalsi_Seal_application_examples

kalsi产品手册

 Kalsi Seals Handbook

Chapter A3 Kalsi Seal application examples 

Revision 0 April 18, 2012

Individual chapters of the Kalsi Seals Handbook are periodically updated. To determine if a newer revision of this chapter exists, please visit .

NOTICE: The information in this chapter is provided under the terms and conditions of the Offer of Sale, Disclaimer, and other notices provided in the front matter of this handbook.

Document 3050 © 2012 Kalsi Engineering, Inc. All rights reserved.

kalsi产品手册

Kalsi Seal application examples

Chapter A3 Page 1

1.

Introduction

Kalsi Seals are widely used in the harsh, unforgiving conditions of oilfield drilling and production, where reliability is critical. These seals have made a number of equipment innovations technically and economically feasible. They are also employed in difficult rotary sealing applications in other industries, such as construction swivels, rock drilling machines, machine tools, and submersed dredge pumps. Examples of several sealing applications are described in this chapter.

2.

Mud motor seals

How sealed bearing mud motors work

Mud motors (Figure 1) are used for various drilling tasks such as straight hole, horizontal, directional and short radius oilfield drilling, river crossings and other utility drilling. They are connected to the drillstring to rotate and steer the drill bit. Rotation is provided by a power section, which is typically a progressive cavity positive displacement motor that uses the flow of the drilling fluid to produce rotation. Drilling loads are reacted to the drillstring via the sealed bearing assembly.

A small bend angle between the power section and the bearing assembly gives mud motors the ability to selectively drill curved or straight holes. Drillstring rotation produces a straight, slightly oversized hole. If the drillstring is not rotated, the hole curves in the direction of the bend. The driller references data from a measurement while drilling (MWD) tool in order to steer the mud motor to the target zone.

Advantages of sealed bearing mud motors are:

? Compact size, which facilitates short radius drilling

? Greater efficiency, due to reduced bearing friction

? Lower repair and maintenance costs

Challenges faced by mud motor seals

Sealed bearing-type mud motors have several rotary seal locations, and all are critical to reliability. Two locations are exposed to severe abrasives, and all locations are subject to shaft motion resulting from drilling forces and power section rotor thrust and nutation. Each seal location also has its own unique challenges, including high differential pressure at the fixed location seal, and reversing pressure and sliding motion at the piston-mounted seals. The lack of reliability and short life of conventional seals had previously limited the acceptance of sealed bearing mud motor bearing assemblies,

kalsi产品手册

Kalsi Seal application examples

Chapter A3 Page 2

but the Kalsi Seal has allowed sealed bearing assemblies to attain widespread use. The reliability, ease of maintenance, and economics of the Kalsi Seal have been proven by the significant population of motors that use them today. Kalsi Seals represent the state of the art in mud motor seals. Runs in excess of 500 hours have been achieved by several customers.

Figure 1

Schematic of a typical oilfield downhole drilling mud motor

Mud motor piston seals

The pressure compensating piston balances the lubricant reservoir pressure to the high pressure of the drilling fluid within the drillstring bore. The optional barrier piston balances the barrier lubricant to the pressure of the drilling fluid within the annulus of the well, providing a clean lubricated environment for the fixed location rotary seal. The barrier piston also limits the lateral deflection of the shaft. Because of the reversing pressures experienced by the rotary seals, axially constrained or axially spring loaded Kalsi Seals are recommended for mud motor piston sealing.

Mud motor high pressure seal

When the surface mud pumps are running, the drilling fluid flows down through the drillstring and mud motor power section, exiting into the annulus of the well through the jets (not shown) in the drill bit. The annulus pressure is substantially lower than the drillstring bore pressure due to the pressure drop that occurs as the drilling fluid passes through the drill bit jets1. This differential pressure is borne by the fixed location Kalsi Seal. The return flow of the drilling fluid in the annulus carries drilling cuttings to the surface. The drilling fluid flow through and along the outside of the assembly provides cooling to the bearings, rotary seals, and drill bit.

1 The formula for determining pressure drop across the bit is provided on page 256 of Preston L. Moore's book

"Drilling Practices Manual"

, Second Edition, (Tulsa, OK: Pennwell Publishing Co., 1986.).

kalsi产品手册

Kalsi Seal application examples

Chapter A3 Page 3

3.

Seals for advanced rotary steerable drilling systems

Various companies have developed advanced rotary steerable drilling systems for the oilfield that accurately steer the rotating drill bit to the desired coordinates within a geological formation using surface commands. A typical rotary steerable tool incorporates a drill-string driven rotary shaft that rotates the drill bit. Various types of actuation systems are used steer the assemblies.

Rotary steerable tools eliminate the sliding drillstring mode associated with conventional mud motor steering methods. Since the drillstring continually rotates, such systems provide better hole cleaning and less chance of differential sticking. This allows extended reach wells and complex well trajectories to be drilled more efficiently, with less risk and significant cost savings. Rotary seals are a critical element these expensive systems, and Kalsi Seals provide the reliability necessary to protect the complex internal components.

4.

Centrifugal pump seal cartridge

Figure 2 illustrates a patented centrifugal pump seal cartridge that is used on charging and mixing centrifugal pumps on oilfield well-cementing trucks. This same basic technology is applicable to other centrifugal pump applications.

A pressurized lubricant (typically 60 psi) is introduced between the pair of Kalsi Seals. During rotation, the High Film Seal (Figure 3), acting like a miniature pump, pressurizes, lubricates and flushes a pair of conventional lip seals that face the pump casing and impeller.

A Filled Kalsi Seal is used on the air-side of the cartridge to retain the pressurized lubricant while operating with low torque and low hydrodynamic pumping related leakage. Seal cooling is provided by a shaft-driven rotating fan, a thick mounting flange that transfers heat to the pump casing, and heat draw through the shaft to the slurry-immersed pump impeller.

Comparable designs are possible for pumps where the stuffing box and rear wear plate are integral. The cartridge overcomes the key limitations of conventional cement pump sealing, and has the following advantages:

? Provides a longer-lasting air-side pressure-retaining seal,

? Automatic pressurization and flushing of the lip seals during rotation, as a result

of the High Film Kalsi Seal,

kalsi产品手册

Kalsi Seal application examples

Chapter A3 Page 4

? Meters the flow of lubricant across the lip seals during rotation,

? Provides a liquid-tight seal when rotation is stopped,

? Provides improved heat transfer and reduced seal temperature, resulting in

significantly longer life than conventional sealing arrangements.

? Reduces pump maintenance costs.

Figure 2

Centrifugal pump seal cartridge

In the cement pump seal cartridge, a Filled Kalsi Seal retains the

pressurized lubricant, and a High Film Kalsi Seal flushes and

lubricates a pair of lip seals that face the pump casing. Seal

cooling is provided by fan driven air flow, by immersion of the

end of the shaft in the cement, and by contact between the

mounting flange and the pump casing.