The document discusses optimizing seal design for HPLC (High Performance Liquid Chromatography) and UHPLC (Ultra High Pressure Liquid Chromatography) pumps, highlighting critical performance factors and design insights necessary for preventing leakage and improving pump accuracy. It emphasizes the importance of material choice, alignment, and innovative features like active wash systems to prolong service life and enhance performance. Recommendations are provided for collaboration with Bal Seal Engineering to meet specific sealing requirements and ensure high-quality prototypes.

1. Optimizing Seal Design for Improved
HPLC & UHPLC Pump Performance
Sarah Smith, Global Market Manager
Bal Seal Engineering, Inc.

2. Slide 2
Major Liquid Chromatography Types
• HPLC (high performance liquid chromatography)
 Multi-industry usage
 Drug development
 Forensic analysis
 Food science
• Preparative HPLC
 Higher flow rate
 Purification process
• UHPLC (ultra high pressure liquid
chromatography)
 Higher pressure rating
 Lower flow rate

3. Slide 3
HPLC Pump Environments
• Operating conditions
 Variable flow rates present
 Medium-speed reciprocation
 Small shaft diameter
 Tight leakage criteria
 Wide range of pressures
• Media
 HPLC solvents
 MeOH
 ACN
 H2O
• Performance criteria
 1M+ cycles - depending on media,
flow rate, and pressure

4. Slide 4
Seals: A Critical Element
• Seals prevent mobile phase from
leaking into the back of the pump
• Seal failure adversely impacts
pump precision, consistency and
accuracy
• Seal designs for HPLC must:
 Mediate friction and sealing
effectiveness to guard against leakage
in pressures from aspiration to 20 kpsi
 Maintain eluent pressure consistently
for 1 million+ cycles
 Resist wear in aggressive HPLC
solvents and buffers
 Minimize shedding to reduce process
contamination

5. Slide 5
Sealing Performance Factors
• Housing surface
 Suggested static sealing surface is 9.1 – 14.5 µin Ra
• Plunger surface
 Smoother surface finish is better
 Suggested dynamic surface is 7.3 - 14.5 µin Ra
 Minimum shaft hardness is 40Rc for soft materials (for
virgin PTFE or UHMW PE)
 Higher surface hardness enhances seal performance

6. Slide 6
Sealing Performance Factors
• Plunger material
 Sapphire is preferred
 70Rc hardness & 2 µin Ra surface finish
 Ceramic with minimal porosity
 Smaller grain size preferred

7. Slide 7
Sealing Performance Factors
• Plunger alignment
 Minimal shaft to bore
misalignment
 Floating plunger
 Tight concentric guidance
(<.002 in) between wash body
& pump head
 High modulus backup support
ring to improve extrusion
resistance
• Media viscosity
 Low viscosity media reduces
sealing contact stress
 High viscosity media increases
sealing contact stress

8. Slide 8
Design Insight
• Incorporating active wash system with rinse seal:
 Reduces heat generated under pressure
 Prolongs service life
 Adds lubricity to the application

9. Slide 9
• Geometry
 Flange design to reduce pulsation
 Short ID lip reduces friction
 Long ID lip increases contact area
• Jacket material
 Filled PTFE materials (graphite, polyimide)
 Chemical resistance to HPLC solvents & buffers
 Temperature resistance to 315 °C
 UHMW PE materials for higher pressures +10 kpsi
 FDA compatible material for pharmaceutical & food analysis
 Temperature resistance to 80 °C
• Spring energizer
 Chemical compatibility
 Biocompatibility
 Corrosion prevention (hardware)
 Consistent spring force
 Customizable loads
Seal Design Considerations
LC
GFP - graphite
UP30 - polyethylene
Canted coil spring energizer

10. Slide 10
UHPLC Enhancements
 Higher pressure variation in UHPLC
 Lower flow rate & smaller particle sizes
 Higher sensitivity, more sample throughput, less
analysis time

11. Slide 11
Seal Design for HPLC vs. UHPLC
• HPLC Seal
 Flange design
 Longer seal ID lip
 Polymer backup ring
 Higher amount of
contact stress
• UHPLC Seal
 Non-flange design
 Shorter seal ID lip
 Metal or ceramic backup ring
 Concave back to handle
higher pressure distribution

12. Slide 12
Optimizing HPLC Seal Design
Requirements Solutions
• Medium-speed
reciprocation
• Chemical
compatibility
• Medium-friction
• FDA compliant
• Biocompatible
• 1 Million+ cycles
• Bal Seal® spring-energized PTFE or UHMW PE seal
• Filled-PTFE (GFP graphite-filled or SP191 polyimide-filled)
• Low coefficient of friction, chemically inert, highly
compatible with aggressive media
• Filled-UHMW PE (UP30 high performance polyethylene)
• Low permeability, higher pressure resistance, minimal
extrusion, compatible with HPLC solvents
• Meets medium drag force requirements
• Flange design simplifies installation and reduces pulsation
• Bal Spring® canted coil spring energizer (MP35N® or Hastelloy®)
• Applies consistent sealing pressure over large tolerance range
• Large variety of bio-inert spring materials for chemical resistance

13. Slide 13
Summary & Recommendations
• To eliminate costly mistakes and delays,
consider sealing requirements as part of
overall pump design
• In early design stages, collaborate with
Bal Seal Engineering to:
 Get consultative engineering advice
 Pump hardware design review
 Finite Element Analysis for theoretical
calculations
 Collaborative seal design discussion
 Custom design a seal that meet all your
system/application requirements
 Determine recommended test failure criteria
 Produce high-quality seal prototypes
 Set AQL of 1.0 C=0
 Test to verify performance
 Drag force evaluation at no pressure
 Scale up to full production

14. Slide 14
Resources & Contact Information
Sarah Smith
Global Market Manager, Analytical
Bal Seal Engineering, Inc.
ssmith@balseal.com
+1 949.460.2226
marketing@balseal.com www.balseal.com +1 949.460.2100 Design request form

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or caused to be manufactured, by any other party.