by Denise Sullivan Denise Sullivan No Comments

HPLC Spring Energized Seals

HPLC spring energized seals

High-performance liquid chromatography is the ideal method for analyzing various solutions in different fields. This machine, however, requires HPLC spring energized seals that adhere to strict guidelines with slight variation.

Different Liquid Chromatography Types

There are a few different types of liquid chromatography. The primary liquid chromatography types include high-performance liquid chromatography (HPLC), preparative HPLC, and ultra-high-performance liquid chromatography.

High-performance liquid chromatography is used in multiple different industries. HPLC is found in food science, drug development, and forensic analysis. It is used to separate compounds and used for quantitative and qualitative analysis.

Preparative HPLC is used in purification applications as it requires a higher flow rate. This liquid chromatography is also used to separate and collect high-purity compounds. It is also used for large quantities of compounds needed for evaluation and analysis.

Ultra-high-performance liquid chromatography (UHPLC) is similar to HPLC. It is used to separate different constituents of a compound and to identify and quantify the different components of a mixture. 

Operating Conditions

HPLC pumps operate in conditions with variable flow rates and small shaft diameters. They have tight leak criteria and operate under a wide range of pressures. HPLC pumps have a medium-speed reciprocation.

Seals in HPLC pumps must withstand the solvents used to separate compounds dissolved in the liquid sample. Solvents used in HPLC include 

  • MeOH (Methanol)
  • ACN (Acetonitrile)
  • H2O (Water).

The expected lifetime for seals in HPLC pump environments is a minimum of one million cycles. Seals may last longer depending on the flow rate, pressure, and media.

Seal Designs

HPLC seals prevent leaks from occurring. Should the mile phase lack into the back of the pump, it will impact consistency, accuracy, and pump precision. To effectively prevent leaks, seals should have effective leak resistance in pressures up to 20 kpsi.

Seal Geometry

The geometry of the seal is an important factor. For HPLC pumps, a flange design helps reduce the pump’s pulsation. HPLC spring energized seals have a longer seal ID lip and a polymer backup ring to increase the amount of contact stress.

UHPLC seals have a non-flange design and a shorter seal ID lip. Instead of a polymer backup ring, it uses a ceramic or metal backup ring. These seals have a concave back for higher-pressure distribution.

Jacket Materials

HPLC pumps’ seals have a PTFE or UHMW PE jacket. The UHMW PE material is used in systems with pressures greater than ten kpsi. UHMW PE is an FDA-compatible material for both food and pharmaceutical analysis.

PTFE jackets are the most chemical resistant of the common materials. The PTFE jackets are filled with graphite or polyimide. These fillers are heat and wear-resistant and work well in liquids and steam.

Performance Factors

Sealing performance factors are affected by the different surfaces in the HPLC pump. The housing surface has a suggested static sealing surface between 9.1 to 14.5 μin Ra.

On the plunger surface, a smoother surface is best. For virgin PTFE or UHMW PE, a minimum shaft hardness is 40Rc. The suggested dynamic surface is 7.3 – 14.5 Ra μin.

 

Medium Dynamic Surface Static Surface
Reciprocating Rotary
RMS  Ra μin  RMS Ra μin  RMS Ra μin 
Liquids 8 to 16 7.2 to 14.4 8 to 12 7.2 to 10.8 16 to 32

14.4 to 28.8

Plunger alignment needs to have a minimal shaft-to-bore misalignment with tight concentric guidance between the wash body and pump head. For best sealing performance, the shaft-to-bore misalignment should be kept to a minimum. 

Shaft To Bore Misalignment at the Seal Area
Shaft Diameter (in inches) Shaft to Bore Misalignment (in inches)
0.000 – 0.750 0.0020
0.751 – 1.500 0.0025
1.501 – 3.000 0.0030
3.001 – 6.000 0.0035
6.001 – 10.000 0.0045

 

HPLC Spring Energized Seal Recommendations

The HPLC spring energized seal requirements should be considered during the pump design process. Designers should collaborate with seal engineers early in development. Contact us today to get a quote on your next custom seal needs. 

 

PTFE Seals for the Oil and Gas Industry
by Jackie Johnson Jackie Johnson No Comments

The Benefits of PTFE Spring Energized Seals for Oil and Gas

In the oil and gas industry, having seals that can withstand the extreme environments found in the industry is imperative. PTFE spring energized seals provide the wear resistance and more needed, which is why many engineers are turning to PTFE spring-energized seals for oil and gas operations.

In this post, we are going to take a look at why based on the three key factors for seal selection: temperature, pressure, and media.  

The Problem with Oil and Gas Seals

As competition for natural resources increases, petrochemical companies have begun to look to new locations that pose new challenges, from arctic operations with low ambient temperatures to subsea equipment with high pressures and extreme temperatures.

In addition, companies face higher demands for safety, reliability, and environmentally-friendly designs and processes. On top of that, there is also the challenge of reducing the footprint of structures and equipment for exploration and production of oil and gas. All of these factors combined have driven up the costs involved in exploration and production, and made the design of oil and gas systems far more complex.

The design and selection of appropriate seals is key to many of these issues…

When seals malfunction, unpleasant things result:

  • personal safety hazards,
  • explosions and fires,
  • damage to local ecosystems,
  • downtime,
  • and repair costs.

The solution? PTFE spring energized seals!

Wide Range of Temperatures

Temperature is one of the key aspects of selecting a seal in the oil and gas industry. High temperature steam can cause a seal to become brittle and crack.  Temperatures below the glass transition temperature of a seal can cause a seal to behave as a brittle material, resulting in unexpected failure.

Polytetrafluoroethylene PTFE (Teflon) behaves differently from other plastics when it comes to its behavior at extremely high and cryogenically low temperatures.  There is still considerable debate over what its glass transition temperature is, but researchers agree that it can hold its strength at higher temperatures than most polymers, and still behave in a ductile manner at lower temperatures.

There are several different types of PTFE polymer seal jackets are available for spring-energized seals.  They cover a range of temperatures; for example, polyimide filled PTFE can function in temperatures down to -450° F while glass/moly PTFE can operate in temperatures up to 500° F.

Key Factor #2: Pressure Issues

Pressures between 1,500 psi and 15,000 psi are becoming commonplace, with some applications pressures are up to 25,000 psi. PTFE seals offer excellent performance at both low pressures, where the spring energized seals support sealing even at low temperatures and high pressures.

Pressure specifications for a seal are not just limited to the sealing capabilities, but can affect other properties as well.  For example, pressure can affect the glass transition temperature of a polymer: high pressures can drive down the glass transition temperature of a polymer, causing it to exhibit unexpected brittle behavior.  This is especially critical in sub-sea environments.

Another issue with pressure is extrusion.  There are certain types of filled PTFE that offer extremely high resistance to extrusion: Moly-Filled PTFE, Glass-Moly PTFE, and Polyimide-Filled PTFE.

Key Factor #3: Media

In the oil and gas industry, seals are going to be exposed to chemically aggressive media.  Sour gas and acid gas are some of the most chemically aggressive materials encountered in this industry, but PTFE spring energized seals are resistant to their attacks.  When media such as this are combined with high pressures and extreme temperatures, PTFE still performs well. And the energized springs in the seal help keep it’s form even when exposed to such harsh chemicals.

Conclusion

Oil and gas companies are faced with increasingly complex challenges, and to meet those challenges they need cutting edge equipment with reliable components. PTFE spring energized seals are one of those components, providing a leak-tight seal, excellent performance over a wide range of temperatures, and compatibility with many corrosive chemicals encountered.