Reusing a Helicoflex gasket

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Can you re-use a Helicoflex gasket?  The answer is yes, sometimes.

A Helicoflex gasket uses the concept of plastically deforming to seal between two flat and polished surfaces instead of the much more common knife edge seal used with copper gaskets and CF flanges.

On Physical Electronics X-ray Photoelectron spectrometers Helicoflex gaskets are used on the monochromator, the SCA (spherical capacitive analyzer) and the LS specimen stage.

Here is a link to information on how a Helicoflex gasket works –  http://technetics.com/products/sealing-solutions/metal-seals/helicoflex-delta/

First of all, Helicoflex gaskets are designed to be used only once.   However,  since these gaskets are expensive it may be worth trying to reuse it as long as you have a new gasket on hand in case the trick I will show  you in this blog post does not work.  My success rate with this trick is about 50%.  RBD Instruments provides most of the Helicoflex gaskets used on PHI XPS systems.

For this example, I will attempt to make it possible to reuse a monochromator gasket as shown in the picture below.

monochromator_gasket

mono-chromator gasket

Note that once compressed, the center surface of the gasket is flattened out.

better_view_of_flat_area

Step one is to uncompress the gasket.   To do that, find a spot on the outside edge of the gasket where you can insert a small screw driver and gently spread open the two lips of the gasket enough to get a large flat head screwdriver inside.

insert_small_screwdriver

Then, carefully work the large flat head screw driver around the perimeter of the gasket until the entire gasket is un-compressed.  Try not to deform the edges of the slit.

insert_large_screwdriver

During this process the gasket will become deformed.  Use a round surface such as a Philips screwdriver to smooth out the bumps without re-compressing the gasket.

smooth_out

Next, using a very fine emery cloth (I used some 30uM 3M sand paper) smooth out the edges of the flat surface on the gasket.  You just want to break the edges, not make it round.

break_edge_on_flat

Clean the gasket with isopropanol or methanol to remove the small particles.

clean_with_IPA

Finally, use a small amount of Apiezon L or other HV or UHV vacuum grease to the surface of the gasket (on the flat area).   You want to use a very small amount and spread it out evenly.  The vacuum grease will help to fill in any small scratches.   Wipe off the inside and outside of the gasket.   You only want a small amount on the flat area.

small_amount_of_vacuum_grease

You are now ready to install the gasket.   Good luck!

The gasket that I used in this blog post did seal fine, so I got lucky.  🙂

 

 

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