Overview
HPLC tee fittings used in high‑pressure areas are actually unions, and these require ferrules to create a proper compression seal.
Low‑pressure tee junctions rely instead on flat‑bottom flangeless fittings, which function well without ferrules due to the minimal pressure involved.
High‑Pressure Zones – Use Ferrules
Characteristics
- These “tee fittings” are technically unions.
- They operate in parts of the system experiencing high HPLC operating pressure.
- They rely on ferrules to ensure a leak‑free, stable connection.
Why Ferrules Are Required
- Compression sealing: Ferrules deform to create a robust seal that handles high system pressures.
- Pressure stability: Prevents leaks that may produce shifting baselines or inconsistent retention times.
- Mechanical integrity: Compression fittings maintain long‑term reliability under continuous pressurization.
Low‑Pressure Zones – Use Flat‑Bottom Flangeless Fittings
Where These Are Used
- Solvent selection valves
- Waste lines
- Atmospheric or auxiliary flow junctions
Why Ferrules Are Not Needed
- Minimal pressure: Low‑pressure conditions allow a simple flat‑bottom seal to function effectively.
- Simplified fittings: Flangeless designs reduce hardware complexity.
- Adequate sealing: Surface‑contact seals are sufficient at low pressure without compression ferrules.
Correct Fitting Selection
Problems When Using the Wrong Fitting
- Leaks in high‑pressure regions
- Pressure drops
- Signal baseline instability
- Risk of fitting blowout
Match the Fitting to the System Zone
- High pressure → Use ferrule‑based unions
- Low pressure → Use flat‑bottom flangeless fittings
Additional Resources
Ordering information and reference images for the appropriate HPLC unions are available. Click HERE for unions for HPLC ordering information and pictures
