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Check out Dual Vespel® Ring Inlet Seals

By
  • Linx Waclaski
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Inlet seals are a critical component for ensuring a leak free seal at the base of a GC inlet.  For those of you who are using standard inlet seals on Agilent or Thermo Trace instruments, Restek also offers an alternative known as the Dual Vespel® Ring seal.  This seal features a Vespel® ring on each side and comes in the same finishes as the standard OEM style inlet seals (gold, steel, Siltek®).  There are a few advantages to using the Dual Vespel® seals over the regular style seals:


Location of the gold dual vespel inlet seal with the arrow pointing to the location of the outside of the liner. Notice the edge of the injection port making contact with the Vespel material.
Figure 1: Location of the gold dual Vespel inlet seal with the arrow pointing to the location of the outside of the liner. Notice the edge of the injection port making contact with the Vespel material.

No separate washer required:

Standard inlet seals require you to place down a spacing washer, followed by the seal in the reducing nut.  With the Dual Vespel® seals, the built in Vespel® ring on the bottom serves as the washer.  One less inlet component to deal with!

 

Requires less torque to seal:

The Vespel® ring on the top provides a softer surface than metal, which allows it to more easily form a seal with the bottom of the lower inlet weldment.  You no longer have to tighten it so hard your whole GC shakes with that last heave!  This also ultimately reduces variability between different operators.

 

Reduces damage to base of inlet weldment:

Because of the higher torque required with the standard seals and the metal on metal contact, you can eventually start to damage the bottom of your inlet weldment.  This can lead to leaks, due to a failure to properly seal. In addition, the Vespel® material is outside of the liner, eliminating potential bleed and activity (See Figure 1).

 

Stays sealed over multiple heating and cooling cycles:

The Vespel® seal has a low thermal expansion coefficient, which helps it to stay sealed over multiple inlet heating cycles.  Metal seals, if not torqued very tightly, can loosen up and introduce leaks.

 

Equivalent cost:

Dual Vespel® seals are priced equivalently to their traditional counterparts, so switching will not increase costs.

 

Disadvantages?:

We have had some customers complain about the seal sticking to the bottom of the inlet (which is another indication of how well this product works!)  If this happens, removal is not difficult.

 


Dual Vespel Inlet Seals come in several different surface finishes.
Figure 2: Dual Vespel Inlet Seals come in several different surface finishes.

 

Technical article: http://www.restek.com/adv009

Product pages: 

Agilent Dual Vespel Inlet Seals: http://www.restek.com/catalog/view/5134

Thermo Dual Vespel Inlet Seals: http://www.restek.com/catalog/view/39954

 

Comments

Tue, Mar 01, 2016

Ok, so that means this seal must withstand a lot of force if someone would use - for example- a vespel ferrule.. I can imagine the ferrule can push-up this seal a little, creating an open pathway or even crushing a liner or create a leak? If graphite ferrule is used, is there not a big chance that graphite gets into the bottom of my liner? I judt like to visualize where the actual seal is made using this dual vespel ring seal..

Sat, Feb 27, 2016

If the seal sticks, how do i remove it?

Sat, Feb 27, 2016

I understood you can use this seal on both sides. So instead of replacing it, flip it first.. It extende life time by another factor 2. Jaap

Tue, Mar 01, 2016

Hi Alan, These will work up to 400 degrees C, Agilent's max injection port temperature. There was no damage done to the inlet/seal or any major off-gassing occurring in the experiments I've performed, though I haven't used them extensively at such high temperatures. If anyone has used these at temperatures greater than 350 deg C, I'd be happy to hear feedback. One thing to keep in mind is that the higher you take the inlet, the more thermal expansion you will get. If you then cool it down to room temperature to change a liner, the chance of the seal loosening increases from such a great change in temperature. So if you do set your inlet to very high temperatures and cycle the inlet temperature, I would check for leaks the first few cycle times and re-tighten if necessary. Thanks for your question! -Linx

Mon, Feb 29, 2016

Hi Jaap, The standard Dual Vespel Ring Inlet Seal cannot be used on both sides, as there is a special seat for the column ferrule on the bottom side, like standard inlet seals (you can see this in figure 2 above). You are thinking of the Flip Seal (<a href="http://www.restek.com/catalog/view/10665">http://www.restek.com/catalog/view/10665</a>), which also has Vespel rings on both sides but does not have the ferrule seat. In order to use the flip seal, you must first purchase a Flip Seal kit, which comes with a special reducing nut that allows the column ferrule to seat to the bottom of the reducing nut, rather than the gold seal. For more info on Flip Seals, check out this FAQ: <a href="http://www.restek.com/Technical-Resources/Technical-Library/General-Interest/general_APP_0066">Flip Seal Inlet Seals Frequently Asked Questions</a> As for removal of a stuck seal, in the simplest case, you can just get a hold of it with your fingers and pull it off. Alternatively, you may be able to use a septum puller style tool to grip it from the bottom and pull it off. If trying to remove it from the bottom doesn't work, you can carefully put a long object like a torx/screw driver down through the inlet (careful not to scratch up inlet walls!) and give the handle a light tap and it should pop right off. If you are frequently getting the seals stuck to the inlet pretty good, you may be over-tightening. Remember, these do not need as much torque as the standard all-metal seals to be leak free. -Linx