Tag Archives: spring energized seals

Spring Types and Materials in Sealing Systems

Springs are an integral part of all sealing systems. A simple air cylinder has O-rings to seal in the air, and the O-ring exhibits spring-like qualities to ensure a good seal over a broad temperature range.

But what are the different types of springs and materials in sealing systems? And how do you choose the best for your application?

image of metal spring types

Metal Springs

Metal springs, such as the Cantilever and Canted Coil spring, are used to energize polymers such as Teflon and ultra high molecular weight polyethylene (UHMW) to allow sealing in a wide range of temperatures. Selecting the correct spring material is critical to the life of the seal.

Metal energized seals are often subjected to a wide variety of fluids and temperature ranges, which then requires the correct material choice for the life of the seal in the application.

One of the earliest metal springs was the flat band or marcel expander, often made from common materials like 300 series Stainless Steel or heat treated 17-7 Stainless Steel.

These materials are often chosen for their tensile strength. But due to the cost to manufacture and the high volumes of spring required, these two expanders were often relegated to industrial or aerospace hydraulic systems.

If system fluids were not compatible with Stainless Steel, customers generally went to a different sealing system to avoid the high cost of short runs in these styles of energizers.

O-Rings cover a wide range of temperatures, and fluids, but generally not both. If there are multiple fluids involved, O-Rings often fail to provide compatibility over a range of fluids.

The use of Cantilever, Canted Coil or Helical coiled spring allowed for long runs and lower costs. The most common spring material is Stainless Steel, but these styles of spring lend themselves to materials that have a wide range of chemical and temperature range while maintaining tensile strength.

Alternative Spring Materials

Some of the more common alternative materials are Hastelloy and Elgiloy. While 17-7 is available, it’s seldom used because Elgiloy (while more expensive per pound) is often run at a higher volume, bringing the overall cost down making 17-7 less attractive due to cost.

Another style metal spring for polymers is the Garter spring. Garter springs are normally run on a per job basis, but because it’s made from wire, it can easily be wound from any material like Elgiloy or Stainless.

Garter springs are often used in rubber style lip seals, but we often find them coupled with polymer-style seals.

Mechanical Seals

Mechanical face seals typically marry a material with the fluids the seal will be running in. Mechanical seals have the overall body and internal springs made from specific materials capable of handling variations in temperature and fluids.

PEEK in Seals

Polymers are thought of as seal materials, but PEEK has been used as a spring in polymer-style seals. PEEK can be wound into helical style springs, and also formed into cantilever springs. As a Helical style, it can be wound into a diameter to energize Teflon or rubber lip seals.

If you consider radiation service, a PEEK spring makes an excellent choice keeping metals out of the seal.

How to Choose the Right Spring Material

While there are a variety of metals, often economics determine the practicality of specialty metals.

A consideration is reviewing the hardware used in the application as to what spring material is acceptable in an application. We often review what the customer is using in the rest of the service for determining a spring material.

Temperature is often a key factor in determining materials for spring. Elgiloy tends to do an excellent job in maintaining tensile strength at elevated temperatures.


The original article can be found on Eclipse Engineering’s website and was written by Cliff Goldstein.

Gallagher Fluid Seals is an authorized distributor of Eclipse engineering. For more information about choosing the right spring material for your application, contact our engineering department today.

Case Study: Replacing U-Cups with PTFE Spring Energized Seals in High Temperature Applications

Being commodity items, U-Cups are readily available in a number of materials and can be found on-the-shelf from multiple distributors and manufacturers in many standard sizes.

Named for the shape of their cross-section, a U-Cup’s design will be pressure energized increasing sealing effectiveness when compared to a standard O-Ring.

This means as pressure increases, the sealing lips are continually forced into the mating hardware surface, ensuring good contact at all times.

The simple and easily moldable design is an effective sealing solution to many systems in both hydraulic and pneumatic applications. Modifications in lip thickness and inclusion of an O-Ring Energizer can tailor sealing loads and wear life to specific situations.Spring Seal and U Cup

A key advantage to an elastomeric U-Cup is the relatively small and simple hardware space needed. Because of their flexible compounds, most U-Cups can be installed in a solid gland configuration.

A basic ID or OD groove is all you need for proper seal retention. Plus, no special tools or considerations need to be taken for correct installation.

U-Cups are available in many of the same compounds as standard O-Rings such as Nitrile, Fluorocarbon, and EPDM, but polyurethanes may be the most common material.

Urethane provides a good combination of elasticity/pliability and toughness. Therefore, it exhibits good sealing characteristics as well as, durability and wear resistance.

These desirable qualities make U-Cups an optimal solution for many sealing systems across multiple industries and they can be found in countless standard products. But Eclipse is approached many times a year with customers pushing the limits of standard U-Cups and in need of better solutions.

The Client’s Issue

Eclipse was approached by a leading pneumatic cylinder manufacturing seeking a sealing solution for a unique application.

While U-Cups typically provide optimal sealing performance in pneumatic cylinders, this application presented a difficult challenge.

The air cylinder was to be used as an actuator for a latch on a large industrial oven. While pressures, speeds, and cycle times were nothing out of the ordinary, the temperature at which it had to operate at was — a continuous 500°F.

Continue reading Case Study: Replacing U-Cups with PTFE Spring Energized Seals in High Temperature Applications

Preliminary Considerations for Spring-Energized Seals

springsealsToday we’ll continue our look at spring-energized seals by exploring some of the preliminary considerations to made when working with these seals.

A spring energized PTFE seal is selected to fit an exact set of service conditions found in your application.

Gallagher Fluid Seals recommends conducting a review of the entire sealing environment. You should use the Engineering Action Request (EAR) form before selecting a seal design.

Continue reading Preliminary Considerations for Spring-Energized Seals

New Video: Spring Energized Seals


 

Gallagher Fluid Seals is happy to introduce its latest video, which deals with spring-energized seals.

In the clip above, Gallagher Engineering Manager Craig Beil discusses these seals and the tools and materials used to manufacture them. Gallagher can meet your requirements for PTFE sealing in most, if not all, environments and operating conditions.

Be sure to watch our previous videos on GORE expanded PTFE seals and static seal gaskets to learn more about our products.

And don’t hesitate to contact Gallagher with any questions, whether they’re about spring energized seals or any other product or service. We’ll be happy to hear from you.

What is a Spring Energized PTFE Seal?

spring

Spring energized PTFE seals perform reliably in a variety of applications where conventional elastomeric seals fail due to chemical attack, extreme heat or cold, friction, extrusion or compression set.

PTFE seals have three basic design elements:

  • A pressure-actuated U-shaped jacket
  • A metal spring loading device
  • High performance polymeric seal materials

So what is a spring energized PTFE seal? It’s a spring-energized U-cup that uses a variety of jacket profiles, spring types and materials in rod and piston, face and rotary seal configurations. They are used when elastomeric seals fail to meet temperature range, chemical resistance or friction requirements.

Jacket profiles are made from PTFE and other high performance polymers. Spring types are available in corrosion-resistant alloys, including stainless steel, Elgiloy and Hastelloy.

Continue reading What is a Spring Energized PTFE Seal?