Can I use a propane hose in my CNG system?

[srhaas]

Hi!

I am currently getting my CNG stove set up. As a note, I have a nautical shop near by that has a CNG rotation program so I have plenty of gas.

As you can see in the picture, I have a CNG regulator with a 2 ft propane gas line. This hose will run to a solenoid, which will run to the oven.

All the fittings are snug and the individual at the hardware store I went to noted that the use of this line should be fine for CNG...

I dont want to install until I am certain, so I wanted to reach out and see if anyone sees any issues in this system?

[Westcliffe01]

What is the pressure of the CNG you have to work with ? Surely the pressure of the gas in the CNG tank will be much much higher than any propane system ???


Usually the working pressure for an appliance is 0.25psi with NG. But the pressure in the CNG tank may be thousands or tens of thousands of PSI, more like what you get in an oxygen cylinder...

[GordMay]

According to Parker Industrial Hose:
Compressed Natural Gas (CNG) and LP Gas Hose
Do not use LP Gas hose in any CNG application, including fuel dispensing, on-board vehicle fuel lines, and fuel transfer.
➥ http://www.squibbtaylor.com/uploaded...ty%20Guide.pdf

[srhaas]

Thanks Gord! I'll take my business to https://www.centralstateshose.com/ for anyone else that is looking for hoses for their gas systems!

[Dsanduril]

Do note that in Gord's linked document Parker makes a distinction between NG (natural gas) and CNG (compressed natural gas). For NG they say:

Natural Gas and LP Gas Hose
The molecules of natural gas are small, enhancing their ability to permeate through standard rubber or PVC hose constructions. The permeation process is more rapid as the working pressure increases, and natural gas accumulates with potentially dangerous consequences. Series 7132, 7132XTC, 7170, 7231, 7232, 7233 and 7243
LP Gas hoses may be used for natural gas service to a 350 psi maximum, but ONLY under ALL of the following conditions:
• Use only in a well-ventilated environment: Outdoors, or indoors with significant continuous air movement.
• Do not use LP Gas hose to replace fixed/rigid pipe where that material is more appropriate due to reduced permeation, overall strength and durability. Use rigid pipe, non-permeable tubing or hose with barrier constructions to convey natural gas whenever possible.

I suspect that in the OP's case Parker would consider the downstream side of the regulator to be NG, since their discussion of using propane hoses for NG service goes to 350psi. Downstream of the regulator, LPG or NG should be less than 1 psig.

There are certainly hoses out there that are dual-rated (Amazon shows a fair number of hits at quick glance) so the prudent thing might be to select on of those.

[kmacdonald]

My CNG system uses gray push on fittings and hose. Very easy to work with and repair. No clamps.

[srhaas]

Hi! Would you mind sending a picture of your system?

[kmacdonald]

It's the same gray hose and connectors as between you first and second stage regulator shown in your picture.

[kmacdonald]

On the second stage regulator, where the gray hose attaches, there should be another gray hose attached to the same fitting and vented overboard. If the regulator fails, gas is vented out there. Your black hose can be replaced with the gray push on hose and fittings.

[srhaas]

The regulator actually had (still have in toolbox) the extra grey hose, but it was cut at the end and didnt have a vent attached.

[guyrj33]

I was told the gray CNG hose shrinks when exposed to fire, cutting off the flow of low pressure gas in the hose.
CNG tanks we're familiar with fill to 2200lbs/sq in.