OXYGEN LINE TO CABIN GAUGE CAME OFF - ANY IDEAS?

**LANCECASPER** · February 14, 2016

While re-installing my interior I was gently straightening the line going to the gauge so I could re-install the gauge to my side panel. I heard a hissing and before you know it, the line shot off and of course my oxygen depleted.

Any ideas on how to repair this?

Edited February 14, 2016 by LANCECASPER

Marauder · February 14, 2016

It looks like an 1/8" Swagelok fitting. You will need a tubing cutter (without any cutting oils on it), front and back ferrule and you can re-use the nut.

The last picture shows the front ferrule stuck in the fitting. You will need to remove it. Be careful you don't damage the elbow fitting.

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Marauder · February 14, 2016

Use a small needle nose plier to remove the front ferrule.

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Marauder · February 14, 2016

If the nut is not messed up, you will need to cut the end of the tube, put on the nut, a new back ferrule and a new front ferrule. Here is what the back and front ferrules look like: https://www.swagelok.com/en/catalog/Product/Detail?part=B-200-SET&item=

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Marauder · February 14, 2016

What you are seeing in picture 1 is the broken off copper tube and the brass front ferrule. I would replace all 3 components if you can't tell the quality of the nut. The front and back will need to be replaced. And since this is carrying O2, it needs to be free of oil and any other contaminants.

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Marauder · February 14, 2016

This is the nut: https://www.swagelok.com/en/catalog/Product/Detail?part=B-200-P&item=

I can't tell from the pictures if this a Swagelok fitting. Parker Hannefin also makes these. Swagelok usually puts there name on the nut. Like in the picture.

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**N201MKTurbo** · February 14, 2016

That is a Parker fitting.

I beleve the ends on those fittings are silver soldered on. Aircraft Spruce sells the fittings, but you have to dig deep to find them.

**carusoam** · February 14, 2016

That is the kind of simple failure that keeps me from wanting to fly at the really high altitudes without a solid O2 Plan B.

Looks like the copper tube cracked and broke similar to a stress fracture started by the ferrule that was compressed Around it. Is there a 1/8" piece of copper tube sticking out the other side of the ferrule left in the elbow?

Saw a similar stress crack happen in a soft Aluminum MP line... The crack initiated at the tiny seep hole though... odd how the crack propagates through a soft metal...

Chemical engineering generally allows for the re-use of the threaded parts. the smooth surface compression parts are a one time use only kind of thing. They get lines in their surfaces that would make it difficult to reseal properly a second time.

When you take the threaded parts out, look for any lines in the smooth surfaces of the threaded parts that may cause difficulty sealing when re-using, the threaded part. (Being Really clear about re-using the threaded parts, not the compression parts). Sometimes, the assembly of these parts goes awry. It may take following instruction, some practice, and some paying attention when putting them together. Buying an extra set of ferrules is a good idea in the event the first set gets used up 'practicing'.

Also note, on compression fitting use... These are built by companies that use their own design standards. Mixing ferrules with nuts from different companies may cause some unexpected challenges. Consider buying the whole elbow, nut and ferrules as a unit to minimize design and size issues. It probably costs a few dollars, not AMUs.

I got my training on compression fittings by a Parker Hannefin sales engineer...(1986: Mark Dinnerman if he's watching)

Best regards,

-a-

**carusoam** · February 14, 2016

Swagelock fittings currently get their name molded or laser etched on the side of the brass elbow...

https://www.swagelok.com/en/search?Ntt=90°%20Elbows&language=en

Parker Hannefin puts a nice catalog together where you can probably find the exact elbow you have photographed...

http://www.parker.com/literature/Brass%20Products/3501E-G.pdf

I would think the MM will say exactly what manufacturer and part that is.

I am more impressed each day with the skills that Marauder comes with!

Keep in mind I am only a PP, not a mechanic.

Best regards,

-a-

Marauder · February 15, 2016

If it is a Swagelok fitting, it will have "Swagelok" embossed on the nut like this;

I don't have a 1/8" copper tube to show how they are assembled but I put a set on a paper clip in the correct orientation.

Make sure the end is cut flush and the opening is open. Assemble the tube through these fittings in this orientation. The tube should bottom out in the bigger fitting. Push everything towards the fitting and start tightening it. Just don't over tighten.

Based on the picture you are showing, these are not silver soldered ends. Just a straight compression fitting.

If these are Sawgelok, let me know and I will send you the fittings I showed in my photo.

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kortopates · February 15, 2016

2 hours ago, carusoam said:

I would think the MM will say exactly what manufacturer and part that is.

Exactly right Anthony, but IPC rather than MM. It may not say Swagelock but it will have the fitting part no's that will match one of the manufacturers.

If it every happens again, or to someone else, the loss of O2 out of the tank could have been prevented by disconnecting the HP line at the tank, A HP needle valve on the regulator prevents the tank from discharging. Its such a restricted orifice that would take several minutes to discharge anyway.

Edited February 15, 2016 by kortopates

**Deb** · February 15, 2016

The expertise of the respondents is amazing!

As Marauder said, since this is carrying 100% oxygen, all the components need to be free of oil (hydorcarbon) contaminants. In the dive shop, we use Dawn or a similar detergent.

**N201MKTurbo** · February 15, 2016

Most of the high pressure fittings used in Mooneys are AN-800-3 cones with AN-805-3 nuts braised to 3/32" soft copper tubing.

ive never seen Swagelok fittings in an OEM installation. But the thread pitch of that fitting looks strange, it doesn't look like a Swagelock or an AN 805.

**wpbarnar** · February 15, 2016

Reiterating what Carusoam mentioned it is very important not to mix components of the two manufactures (Parker Hannefin and Swageloc). They look similar and a Parker nut will make up on a Swageloc fitting and vice verse. Swageloc uses a two piece ferrule were Parkers is a single piece. Mixing components will often work initially but inevitably fail later.

I am curious why your's failed like it did. A properly assembled compression fitting will not let the tube blow out of the fitting. After the initial make up, the ferrule will be permanently attached to the tube. If the nut becomes loose, the fitting will leak but the tube and ferrule will still be contained in the fitting.

Bill

**N201MKTurbo** · February 15, 2016

The IPC says the fittings are Scott B200 series. Can't find any info on them.

PTK · February 15, 2016

I could've sworn I've seen compression fittings at Home Depot...!!!

Where's Jose´ when you need him!

**LANCECASPER** · February 15, 2016

Here's what the M20M Parts book shows - Part #46 is the fitting. Then if you google that part number (B-200-8-2), it shows that it's a Swageloc.

Edited February 15, 2016 by LANCECASPER

**LANCECASPER** · February 15, 2016

1 minute ago, PTK said:

I could've sworn I've seen compression fittings at Home Depot...!!!

If they had 1/8" Swagelok high pressure compression fittings, I'd be going to the Aviation Dept. at Home Depot today.

**LANCECASPER** · February 15, 2016

3 hours ago, Deb said:

The expertise of the respondents is amazing!

As Marauder said, since this is carrying 100% oxygen, all the components need to be free of oil (hydorcarbon) contaminants. In the dive shop, we use Dawn or a similar detergent.

Mooneyspace is a great resource!

**N201MKTurbo** · February 15, 2016

Wow, it actually is a Swagelok:

http://www.swagelok.com/en/catalog/Product/Detail?part=B-200-8-2

Yetti · February 15, 2016

Somewhere I am remembering that over tightening a compression fitting like those will cause them to fail like that one did right at the ferrule.

Marauder · February 15, 2016

Somewhere I am remembering that over tightening a compression fitting like those will cause them to fail like that one did right at the ferrule.

I probably have installed 10,000 Swagelok fittings in my career as a service engineer. The two failures I have seen are like you pointed out, over tightening and the second is trying to move or bend the copper tube after the connection is made.

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Marauder · February 15, 2016

Wow, it actually is a Swagelok:
http://www.swagelok.com/en/catalog/Product/Detail?part=B-200-8-2

Yeah, Lance and I figured that out last night. I am sending him some extra fittings I have. Hopefully, it will get him up and running.

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**LANCECASPER** · February 15, 2016

1 hour ago, Marauder said:

I probably have installed 10,000 Swagelok fittings in my career as a service engineer. The two failures I have seen are like you pointed out, over tightening and the second is trying to move or bend the copper tube after the connection is made.

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Trying to move or bend the copper tube is what caused mine to fail

Marauder · February 15, 2016

Lance -- do you know if the post office will take the pre-paid envelope if I drop it in the outside mailbox of the Post Office?

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