Nylon air line and barb size matching?

[julianf]

So, I'm looking at something like this to go over a pre-existing barb -

METRIC Flexible Nylon Pneumatic Air Line Tubing Compressed Airline Plastic Pipe | eBay

Automotive, Agriculture, Aviation, Material Handling, Marine, Mining & Quarrying, Plant & Construction, Rail & Utilities ++. COLOUR & CORRECT SIZE. LONG HOSE . WHY COMPROMISE FIT THE BEST! Audi - BMW Mini - Citroen - Fiat - Ford - Honda - Hyundai - Jeep - Lancia - Mitsubishi - Nissan -...

www.ebay.co.uk

The barb has an OD of 9.06mm on the first ridge, and then 8.44mm on the subsequent ridges (where the hose clamp would locate)

Ive never had a lot of luck heating this stuff with a flame, so i would be planning on getting it over the barb using hot water and cursing alone.

I guess maybe i could use an electric hot air gun, but, again, ive found theres too fine a line between bending and shrivelling with these sorts of things before.



Can anyone with more experience than me tell me what ID i should be going for?

10mm OD in the listing given seems to come in IDs of 7, 8, or 9mm. I guess the "stretchiness" must be a function of wall thickness also?


Im guessing id have issue with stretching 7mm ID up to 9mm to go over the initial barb, so it 8mm ID would be the one, right? Or is there some trick i should be doing?

Thank you.

 

[Trevorleach]

I would use 8mm id.
I fit loads and you never ever heat it, put fitting in a vice pointing up, bit of spit on the barb and a bloody good grip on the pipe and press hard with a gentle wiggling motion and it will fit a treat.

 

[m_c]

If the above doesn't work, put some thick gloves on, dump the fitting and just the end of the hose in some boiling water, and try again.

 

[premmington]

When repairing VAC pipes on cars - I tend to use short lengths of 4mm bore silicon hose as joiners and make new pipes up with hard airline.

What is the application for your project? (fuel pipe I would guess from the size).

I have struggled like #### in the past to do what you are trying to do?

Heat - hot water - never seems to work for me.

 

[julianf]

What is the application for your project? (fuel pipe I would guess from the size).

Yes, it's fuel system stuff. I can't use silicone as it suffers hydrocarbon migration with methyl esters.

(Layman's - they wiggle through it)

I've done the nylon bits before, just not with much enjoyment.

I'll go with 8mm ID upon recommendations here.

Thanks to all.

 

[Robert Weaver]

The options in that eBay ad gives both Id and od. A 8mm pipe has an Id of 6mm.
The 10mm has 7mm id and the 12mm has 9mm id.

 

[8ob]

In the absence of the proper tool you can use a brake pipe tool for pushing on the barbs. No need to heat the pipe, all you reallly need is a straight push, a bit more than you could achieve pushing by hand without screwing the pipe up.

Take another bite.

Job done.

 

[julianf]

The options in that eBay ad gives both Id and od. A 8mm pipe has an Id of 6mm.
The 10mm has 7mm id and the 12mm has 9mm id.

The 10mm has multiple ID options that are, probably, the closest applicable to this job -

10mm OD in the listing given seems to come in IDs of 7, 8, or 9mm

 

[Bornfree]

i always heat the pipe with a flame or hot air gun. but you only heat the very end 1/4" at the most

 

[Woody.v8]

In the absence of the proper tool you can use a brake pipe tool for pushing on the barbs. No need to heat the pipe, all you reallly need is a straight push, a bit more than you could achieve pushing by hand without screwing the pipe up.

View attachment 361260

View attachment 361259

Take another bite.

View attachment 361258

Job done.

View attachment 361257

That's half way how I do them on hgv stuff, I grip the pipe with the collects in the vise then tap the fitting with a rubber hammer as daf recommend, it works surprisingly well.

 

[premmington]

In the absence of the proper tool you can use a brake pipe tool for pushing on the barbs. No need to heat the pipe, all you reallly need is a straight push, a bit more than you could achieve pushing by hand without screwing the pipe up.

View attachment 361260

View attachment 361259

Take another bite.

View attachment 361258

Job done.

View attachment 361257

What a good idea @8ob

 

[8ob]

The 10mm has multiple ID options that are, probably, the closest applicable to this job -

The reason you have options on tube wall thickness is because the tube you are looking at is for push fit fittings ( external) that use the same O/D, the wall thickness is down to the pressure rating for different applications. The type of tube used in cars for vac/fuel is thin wall and the internal size of the barbs matches the I/D of the tube.

Bob

 

[julianf]

The reason you have options on tube wall thickness is because the tube you are looking it is for push fit fittings ( external) that use the same O/D, the wall thickness is down to the pressure rating for different applications. The type of tube used in cars for vac/fuel is thin wall and the internal size of the barbs matches the I/D of the tube.

Bob

Thank you - so i should measure the minor diameter of the barb, not the major, and then match the ID to that... Id entirely overlooked that.

 

[8ob]

Thank you - so i should measure the minor diameter of the barb, not the major, and then match the ID to that... Id entirely overlooked that.

 

[julianf]

Minor diameters are -

7.83mm after the first, initial, barb hook, and then 7.95 after all the subsequent ones.

 

[julianf]

Ive just looked at the sale page for the item, and its listed as "for 8mm (5/16) hose"

The rest of the fitting is UNF, so ill go with 5/16, which is 7.9375 mm

I guess its clearance (just about 0.1mm is less than the thickness of a thick human hair) on the minors and the majors seal?

 

[seriesonewelder]

Method I was shown is to half insert a suitable size drill bit into the pipe and gently clamp in a vice (using protectors) with the open end of the bit vertical and tap the fitting down. The bit guides the fitting into place.
Hope this makes sense.

I've done it a couple of times including on a HGV which was stranded at the roadside with the brakes locked on.

 

[Woody.v8]

From the DAF manual

 

[Ruffian]

10mm pressfit
Usually 1mm (ish wall thickness)

Would warm that up gently and then once over the first barb gently roll it to the fitting.

 

[knighty]

this for bio/veg Julian?

I'd be looking to use larger bore hose than that?