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Filter on molbloc inlet flange, prevent contamination

Current model laminar molbloc elements have an integrated filter in the inlet flange to prevent contamination. It is held in place with a snap ring and is visible when looking at the inlet flange. Applicable molbloc elements are serial number 6000, or higher or have been upgraded with their serial number now ending with a +. Note that the 1E5 laminar molbloc element does not have this filter because its flow paths are large enough to not trap particles of this size.

If you have an older molbloc you can add a similar filter, but it will be external to the molbloc. These are the same filters that are included as part of molbloc mounting systems. They are available for purchase from Fluke Calibration, or from Swagelok. A VCR union and sealing gasket are also used.

See Section 2.3.4 in the molbox1+/molbloc manual regarding gas supply requirements with laminar molbloc elements. From that section:

  • The gas supply must be clean and dry (especially free from oil and particulates) to avoid contaminating the molbloc.
  • Gases with purity of 99.9 % or better are used for molbloc measurements.
  • The test gas should be free of any humidity (dewpoint less than – 40 °C).


0.5 micron filter for low flow molstic-L, 1/4 inch VCR male fittings (flow to 2 slm in air or nitrogen)
Part Number: 3136763
Description: (102457) FILTER,SS,0.5 MIC, 4VCR, SS-4FWS-VCR-05
Swagelok part number: SS-4FWS-VCR-05

2 micron filter for mid flow molstic-L and 1/4 inch molstic-S (flow to 50 slm in air or nitrogen)
Part Number: 3138194
Description: (102857) FILTER,SS,2.0 MIC, 4VCR, SS-4FW-VCR-2
Swagelok part number: SS-4FW-VCR-2

Here are part numbers for o-rings and/or metal gaskets used with molbloc elements and molstic mounting systems. Metal gaskets can be used for connections that are not often changed, or for connections that will be used in excess of 700 kPa (100 psi).

Part Number     Description
3071123              O-rings, 4 VCR (1/4 inch VCR), size 2-202, brown Viton, kit of 50
3071138              O-rings, 8 VCR (1/2 inch VCR), size 2-207 , brown Viton, kit of 50
3135759              102183,Seal,SS,4VCR (1/4 inch VCR) with retainer tabs. Swagelok PN SS-4-VCR-2-GR.
3138203              102858,Seal,SS,4VCR (1/4 inch VCR) without retainer tabs. Swagelok PN SS-4-VCR-2.
3138599              102923,Seal,SS,8VCR (1/2 inch VCR) with retainer tabs. Swagelok PN SS-8-VCR-2-GR.
3135744              102181,UNION,SS,4VCR F-F (1/4 inch VCR). Swagelok PN 4VCR F-F.

See this article for more information on molbloc connections and sealing elements, molbloc and molstic o-rings, and metal gaskets

One more note on preventing contamination of molbloc elements... molbloc elements can be placed upstream of any test devices to prevent contamination - but this is not always possible.

If you believe that your molbloc is contaminated see the article, Purge molbloc - clean contamination from molbloc


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