Table of Contents

Various male fittings used in vacuum applications. Upper left: Swagelok tube fitting, upper right: NPT, lower left: VCR, lower right, VCO

Connector comparison

Swagelok tubing postfix codes [Vacuum Tubing Products]

End Connection(s) Designator
VCR female one end only FR
VCR female both ends DFR
VCR female one end, VCR male other end FMR
VCR female one end, XBA adapter other end FRB
VCR male one end only MR
VCR male both ends DMR
VCR male one end, XBA adapter other end MRB
VCO female one end only FO
VCO female both ends DFO
VCO female one end, VCO male other end FMO
VCO female one end, XBA adapter other end FOB
VCO male one end only MO
VCO male both ends DMO
XBA adapter one end only -B1
XBA adapter both ends -B2

Installation

Tube fittings require simple hand tools as do VCR fittings. VCO are probably just as easy if not easier than VCR

Seal

My guess is that VCR fittings seal best. Tube fittings probably seal pretty good the first time used but may lose their seal if not carefully re-installed.

VCO likely doesn't seal as well as VCR but probably worse than a properly installed tube fitting as well.

Reusability

VCR gaskets should be used fresh for each install but you can probalby get away with reusing the same gasket a few times for most applications. Swagelok tube fittings can be re-installed to the same location as long as they are installed in the same orientation. However, to get a proper tube fitting seal on a new surface with used fittings I imagine you'd have to replace the ferrule which is probably more expensive and labor intensive than replacing a simple VCR gasket.

VCO gaskets/fittings can be reused many times. Gaskets are inexpensive to replace if damaged.

Pressure

Didn't see ratings specific to particular connector types. However, [Vacuum Tubing Products]:

Temperature

[Vacuum Tubing Products]:

Custom builds

Tube fittings are relatively easy to cut and crimp on new fittings.

Unfortuntaley, because VCR glands are special ends larger than the tube itself, they must be TIG welded in place as needed. TIG welding requires equipment and a reasonable amount of skill. I'm guessing that pro shops use orbital welders

Swagelok tube fitting

Above: male Swagelok tube fitting

Very common in many applications, usually with 1/4“ OD tube size.

Components of a connection:

Installing

Steps [STFI]:

  1. Ensure that tubing is bur free
  2. Insert ferrule into mating service
  3. Attach nut but don't tighten it (just needs to guide tube at this point)
  4. Insert tubing into nut against ferrule
  5. Tighten using wrench
    • 1/4”: 1-1/4 turns
    • 1/16“, 1/8”, 3/16“: 3/4 turn
    • Support other side using another wrench or vice

Tip: mark nut with a pen before turning to make it more obvious where in the turn you are

Use Swagelok gap inspection gauge to inspect distance: it should not fit if the fitting is sufficiently tight [STFI]

Re-installing

When disassembling, strip the connection so that original position can be determined

Steps [STFI]:

  1. Insert tube + ferrule assembly into mating service
  2. Slide down nut and finger tight to original position
  3. Tighten it “slightly”

Do not use gap inspection gauge [STFI]

Sourcing

Include:

VCR

Above: male VCR fitting (no gasket installed)

Uses a knife edge on consumable metal gaskets to achieve seal. Most of the part numbers user 1/16's of an inch to indicate size.

Components of a connection [Installing VCR]:

Body has drilled out holes for leak testing.

Since these are knife edges they must be protected against damage. Above: cap to protect edges when not connected

Gasket types

Above: used retainer gasket

Look like washers. Ex:

Types [Installing VCR]:

Materials [Installing VCR]:

Installing

Retainer gasket [Installing VCR]:

  1. Snap gasket onto male gland
  2. Tighten female nut finger tight
  3. Use pair of wrenches to tighten

Side load gasket [Installing VCR]:

  1. Slide gasket onto male gland
    • Tool available to pick up
  2. Tighten female nut finger tight
  3. Use pair of wrenches to tighten

Non-retain gasket [Installing VCR]:

  1. Place gasket into female nut
    • Tool available to pick up
  2. Tighten female nut finger tight. Should engage to last thread if installed properly
  3. Use pair of wrenches to tighten

Flexible tubing

Part numbers:

Because of the gland nature it would seem hard to convert the more readily availble Swagelok tube adapters to VCR fittings without using a separate tube fitting to VCR adapter

Naming seems to follow MAT-OD-X-LENPFX

Naming examples:

VCO

Above: male VCO fitting (no gasket installed)

VCO is similar to VCR except that instead of using consumable metal gaskets it uses o-rings.

References