This presentation examines the impact of seal choice on the overall performance of mud motors, rotary steerable systems, LWD/MWD, and other equipment, and it offers some tips on how to achieve a balance between friction and sealing effectiveness.

1. Rotary Sealing for Improved
Downhole Equipment Performance

2. Slide 2
Downhole Tools & Equipment
• Crucial to the success of the
drilling process, these tools
help monitor and direct the
drill string
• They reach great depths, and
cover long distances
• Examples include:
 LWD/MWD
 Perforating guns
 Mud motors
 Rotary steerable systems
 Tractors
 AUVs

3. Slide 3
The Downhole Environment
• Harsh external conditions
are a designer’s concern,
but so are forces at work
inside the tool:
 Pressure spikes
 High concentrations of H2S
 Side loading
 Varying viscosities
 High temperatures
• These can result in
malfunction/failure, lost
profit, and stalled well
development

4. Slide 4
Rotary Seals: Critical Components
• In downhole tool applications,
rotary seals prevent ingress of
contamination that can damage
motors and electronics
• Seal failure adversely impacts
equipment precision,
consistency, and accuracy, can
result in early breakdown
• Rotary seal designs must:
 Balance friction and sealing
effectiveness to guard against
leakage while enabling smooth
operation
 Withstand pressure spikes
 Resist wear in aggressive media
 Deliver consistent, predictable
service life

5. Slide 5
Rotary Seal Design Considerations
• Geometry
 Shorter dynamic lip reduces friction
 Longer dynamic lip increases contact area
 Locking ring design retains seal through
temperature cycling and pressure environments
• Jacket material
 Polymer-filled PTFE material
 Low friction and stiction
 Minimal wear
 Temperature range to 400°F+
• Seal energizer (canted coil, v-spring,
helical ribbon, elastomeric)
 Corrosion (galvanic) resistance
 Customizable loads
 Chemical compatibility
 Ability to deliver consistent force
Metal
Locking
Ring
V-Spring Seal Energizer

6. Slide 6
Rotary Seal Properties: Impact on Design
• Friction
 Impacts seal life
 Drives component
selection
 Actuators, motors
• Sealing effectiveness
 Inhibits contamination
and corrosion
 Ensures consistent
performance over time
• Wear
 No lubrication required
 Suitable for use in wet
and dry environments

7. Slide 7
Factors Affecting Seal Friction
• Seal material
 Reduces friction coefficient and stiction properties
• Spring energizer
 Customized spring load to minimize friction but maintain
sealing performance
 Potential energizer materials include: MP35N, SS, Inconel &
and Elgiloy to meet downhole needs
• Seal profile
 Machined lip profiles
 Achieve tighter tolerances vs. molded tolerances
 Minimize dynamic lip contact area without compromising
sealing effectiveness
• Hardware
 Material hardness 30 Rc min
 Smooth surface finish
 Greater sealing contact between seal and mating surface
 Improved sealing ability
 Reduced friction
• Other factors
 Thermal cycling
Frictional Force vs. Surface Finish

8. Slide 8
PTFE: An Ideal Seal Material
• PTFE and filled PTFE materials
are ideal for downhole tool
sealing use, because they …
 Have a long shelf life
 Are self-lubricated
 Provide consistent, low-friction
performance
 Resist degradation
 NO age-hardening
 NO rapid gas decompression
 NO special lubrication requirements
(unlike rubber seals)
 Can handle up to 400°F
continuously or 500°F for short
periods at a lower PV

9. Slide 9
Typical Downhole Rotary Applications

10. Slide 10
Case Study: Mud Pulser
Requirements Solutions
Service type =
Dynamic/ rotary
Speed = 200 fpm
Service life = 500
hours+
Media = Resistant to
H2S, drilling mud, hot
water, sand, rock and
debris
Temperature = 350 °F
Pressure = 10 kpsi
Tool diameter = .5” to 3”
Allowable leak rate =
<8 in³ (131 ml)
Seal design recommendation
• Bal Seal® spring-energized LKS® seal
Jacket material
• Machined from graphite-filled PTFE, with
high durability, low wear and low friction,
resistance to broad range of chemicals
Seal geometry
• Custom-engineered rotary lip seal, with
additional stainless steel* locking ring
feature to retain seal, prevent shuttling and
rotation, and protect against breakdown in
thermal cycling conditions
• PEEK backup element to support seal lip,
prevent extrusion
Spring energizer
• Bal Spring® canted coil spring made from
stainless steel*
Summary of results
Up to 150% improvement in seal service life
(over comparable seals)
*If NACE compliance is
required, energizer and
locking ring material
recommendation should
be MP35N® or Inconel®

11. Slide 11
Summary & Recommendations
• To eliminate costly mistakes and
delays, consider rotary sealing
requirements as part of overall
downhole equipment design
• In early design stages, collaborate with
Bal Seal Engineering to:
 Get consultative engineering advice
 Review hardware design
 Estimate frictional outcome
 Perform Finite Element Analysis
 Engage in collaborative seal design
discussion
 Evaluate NACE and NORSOK-compliant
materials
 Custom design a seal that meet all your
system/application requirements
 Determine recommended test failure
criteria
 Produce high-quality seal prototypes
 Scale up to full production

12. Slide 12
Resources & Contact Information
marketing@balseal.com www.balseal.com +1 949.460.2100 Design request form
Jim Harty
Global Market Manager - Energy
Bal Seal Engineering, Inc.
+1 713.446.6227

13. September 19 ©Bal Seal Engineering, Inc. This document contains and/or refers to PROPRIETARY information of Bal Seal Engineering, Inc., and may not be reproduced,
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Products are the subject of issued or pending United States and foreign patents. Products of Bal Seal Engineering, Inc. and this document are PROPRIETARY and products
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