Fluid Gas Handling

Frequently Asked Questions About Seal-Lok for CNG Fittings

Seal-Lok for CNG provides reliable connection in the Alternative Fuel MarketSeal-Lok for CNG Fittings and Adapters provide reliable natural gas fuel conveyance in CNG applications with an O-ring face seal design that incorporates an elastomeric seal compound made of hydrogenated nitrile. Tested and certified by TUV for applicable industry standards, these O-ring face seal fittings offer many benefits like, zero clearance for easy plumbing, resistance to over-tightening and vibration, and unlimited remakability, which make it an ideal hydraulic fluid connection solution. Seal-Lok for CNG leak-free connections reduce warranty costs and maintenance expenditures while providing a competitive advantage for customers in the CNG market.

Below are the most frequently asked questions about Seal-Lok for CNG to give you a better understanding of this reliable leak-free connection solution.


9 Frequently Asked Questions About CNG O-ring Face Seal Fittings - Download the CNG O-ring Face Seal Fittings FAQ Sheet - Parker Tube Fittings Division

Download the full Seal-Lok for CNG Fittings and Adaptors FAQs additional technical information.




Q: What is the O-ring material and stats used for Seal-Lok for CNG?

HNBR compound, 85 durometer, rated for -58ºF to 300ºF (-50ºC to 148ºC).  Parker also has other CNG approved compounds available as specials. Please contact TFD directly if you have specific compound requirements at 614-279-7070.

Q: What fitting materials are approved in this industry?

316 Stainless Steel and Carbon Steel with Parker’s XTR (Zinc-Nickel) plating are both approved.

Q: Is Seal-Lok for CNG NGV 3.1 approved?

Yes. It is approved in -12 and smaller by ANSI NGV 3.1-2014/CSA 12.3-2014 for on-vehicle applications.

Q: What are the part numbers for Seal-Lok for CNG fittings?

  • For Seal-Lok -12 and smaller, add “CNG” suffix to the part number.
  • For Seal-Lok -16 and larger, add “NGO” suffix to the part number.
  • Part numbers can also be built online: Seal-Lok for CNG O-ring Face Seal Fittings and Adapters.
  • For Triple-Lok 37° flare fittings or other fittings requiring the special O-ring material, add the “NGO” suffix to part number.


Q: How do you form the end of the tubing to use with Seal-Lok for CNG?

One of Parker’s three Parflange machines will need to be used to flange the end of the tubing:

  • Parflange 1025, table-top model, automatic, very easy to use.
  • Parflange ECO 25, small table-top hand-pump model, recommended for CNG projects as it is capable of flanging most sizes of SS tubing.
  • Parflange PRO 50, large free-standing production model, is best for hundreds of flanges per day of repeatable operation.

Q: Where can I buy the product or Parker’s Parflange machines?

Through your local Parker distributor. Find the nearest Parker distributor now: Parker Distributor Locator.


Q: Can I use a Parflange machine to flange coiled tubing? What sizes are available?

Yes. Parker has specifically designed one-piece pins for CNG coiled tubing.

  • 3/4" x .104 (ECO 25 or PRO 50).
  • 1" x .139 (ECO 25 or PRO 50).


Q: Can standard stainless steel Parflange pins be used for coiled tubing?

No. Use Parker’s special CNG pins for coiled tubing.

Q: Are the Parflange machines and tooling available to rent?

Yes. Both Parflange machines and tooling can be rented directly from a local Parker distributor.

Q: Are replacement CNG O-rings available?

Yes. Replacement O-rings can be purchased from TFD. Available O-rings are in Parker Catalog 4300. CNG O-rings will need the CNG suffix added to the p/n. For example, 2-014 CNG or 3-906 CNG.


Q: Having passed the bonfire test, Seal-Lok for CNG fittings are approved for use on refuse trucks. What is the bonfire test?

This is a required test for the Pressure Relief Devices (PRD) used on CNG pressure cylinders. At a customer’s request, this test was adapted by Parker TFD to test the performance of Seal-Lok for CNG
fittings in a similar scenario. Seal-Lok fittings were tested with the CNG HNBR seals in a worst-case (1200ºF) fire, followed immediately with a cold-water purge while being continuously monitored for leaks.

Seal-Lok for CNG PASSED the requirements of no leaks and held pressure throughout the required duration.

For more information on bonfire test and specifics about why this was needed, please see our blog post with a test summary: Seal-Lok ORFS CNG Fittings Pass On-Vehicle Fire Safety Test.

Q: Where can I find instructions for how to assemble Seal-Lok CNG fittings?

Refer to the Assembly Section of Parker Tube Fittings Division Catalog 4300. You can also refer to blog post and video “Assembly Instructions for Ensuring Leak-Free O-ring Face Seal Fittings.”

Q: Do the stainless steel fittings have any lubricant on them? What are the recommended lubricants to use for stainless steel fittings?

Yes. Parker’s stainless (SS) Seal-Lok for CNG fittings come with pre-applied Lube-SS on the tube nuts to prevent galling. In addition to the pre-applied product, it is always good practice to use anti-galling lubrication where connecting two SS threaded connections.




Seal-Lok for CNG connection solutions for natural gas


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Cody Yarletts, product manager at Parker Tube Fittings Division

Contributed by Cody Yarletts, product manager, at Parker Tube Fittings Division




Related articles:

Seal-Lok ORFS CNG Fittings Pass On-Vehicle Fire Safety Test
New O-ring Face Seal Fitting Promotes Environmental Sustainability with Alternative Fuel Compatibility
Assembly Instructions for Ensuring Leak-Free O-ring Face Seal Fittings
Tube End Preparation Best Practices for Leak-Free Hydraulic Tube Fitting Connections

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