Scroll pump

Tip seal

One of the biggest issue of owning a scroll pump is tip seals wear out fairly quickly and can be expensive to replace. Many scroll pumps are essentially totaled if kits can't be found readily. This section is about evaluating the merits of making DIY tip seals

Understand wear profile of different materials. Ex: for hobby use a lower grade material may be good enough for low duty cycle

How to know when tip seal is running low without opening / hearing grinding? What it be helpful to install hour counter?

Summary:

• Bush black: 1:1 mix of PTFE and graphite
• Yellow (ex: Edwards XDS 10): probably some Rulon variant
• Someone has tried PU foam, UMHW PE film w/ moderate success

Person Comments:

• We have made our own tip seals before
• Stopped since they seemed to last a little under half as long as the proper ones
• https://www.mcmaster.com/86375K162/
  • Resilient Polyurethane Foam Sheet
  • with Adhesive-Back, Medium, 12" x 12" x 1/16"
• https://www.mcmaster.com/1441T21/
  • Slippery UHMW Polyethylene Film
  • Adhesive-Back, 12" x 12" x 3/64"
• then it's just held in the frame pictured above and waterjet
• the little bit we have left says UH-9, PORON
• I mean we also run 24/7
• so tip seal replacements after about a year of runtime instead of 2-3
• also the DIY ones definitely produced more "dust"

Made-in-China

• Tip Seal PTFE Filled Bronzed Wear Strips Special Designed for Scroll Compressor
• PTFE + Bronze
• Also used in hydraulic cylinders
• "it seems like you can get them in a mix of bronze, carbon, and MoS2"

Anything quick to try?

• https://www.mcmaster.com/o-ring-cord-stock/cross-section-shape~square/
  • Roughly the right size but too high friction
    

Commercial

Sample commercial pricing. Keep distributors anonymous unless they explicitly list pricing

Vendor	Pump	Kit	Price	Notes
Busch	FO 0018 C OHO	Tip seal	$545.00 2021-04
Busch	FO 0018 C OHO	Full	$3928.00 2021-04	How much does a pump cost..
Edwards	nXDS6i nXDS10i nXDS15i & nXDS20i	Tip seal 73501801	$220 2021-05-19
Edwards	XDS10		$353 2021-06-16	Link Anticipated Arrival:  121 on 2021-07-11

Compatibility between these? Could we match one of the less expensive kits to one of the more expensive pump rebuilds?

Manufacturing gaskets

Some suggested that these can only be injection molded

Suspect these can be (waterjet?) cut from sheets or simply applied as strips

Laser cutting probably isn't precise enough and would produce nasty fluorinated fumes

Milling might work (with enough support) but will waste a lot of expensive material

Material (black)

EDS + FTIR analysis indicate this is a 1:1 mix of PTFE and graphite

Busch black gasket material analysis

• Suspected to be bronze filled PTFE
• FTIR has confirmed PTFE is primary organic
• EDS analysis pending

Busch gasket dimensions

• Maybe 2.5 mm => 0.0098" square
• Height
  • Channel: maybe 0.075"
  • Gasket (worn): around 0.080"
• Width
  • Channel: maybe 0.095" wide
  • Gasket: maybe 0.096" wide
• Scroll area: around 7"
• Length needed: around 276" (23')
  • Gasket length: around 69"
  • Gaskets: 4

McMaster-Carr has bronze filled PTFE sheets

Material (yellow)

Edwards XDS 10

• Per pump need:
  • 0.090" wide
  • 0.1055 thick
  • Length: 115"
• New rebuild kit
  • 0.0900" wide
  • 0.1055" thick
  • Remainder: qty 2, 2.5" long each
  • Estimated length: 55 + 2.5 => 57.5"
• Used / near EOL
  • 0.0900" wide
  • 0.0990 to 0.1015 thick
  • Qty 2, 54-55" long each

Scrolls [walls] are anodized aluminum

[gasket] likely Class 3 PTFE filled

that 1045 is even more likely

Rulon J can be made in thin film form

Looking at some rebuild kits

• official kit has green viton orings not brown [for general gaskets]

Other option could be use something like PTFE bronze that could wear off easier but it's 10X cheaper so you would endup changing the seal more frequently but without custom built orders

Yellow gasket

• Suspected Rulon J or XL
• XL - is polymers only
• J has something else
• Rulon 142 has bronze
• New edwards pumps dont use black tip seals
• https://www.idealvac.com/Varian-V70-Turbo-Molecular-Vacuum-Pump-Rebuilt-Repair-Kit/pp/P105145
  • Red stuff is Rulon LR
• https://www.youtube.com/watch?v=ZTUvP2FnfR4
  • Identifying Rulon variants
• https://www.youtube.com/watch?v=zWkPf-5k9RU
  • About Rulon 142

https://info.seals.saint-gobain.com/blog/avoiding-counterfeit-rulon-products