AN to Plastic

[Eric]

To all of you very knowledgeable folks:

If you're running braided hoses/AN fittings, how do you connect to something that has a plastic slip-on fitting? In this specific example, it is a Bosch pump and the inlet/outlet tubes are plastic with a bead clearly intended for a hose to slip on and be secured by a hose clamp. Is there even a way to do this, or do you just use hose clamps and hide the device so nobody can see the clamps?

I apologize, but I am very slowly learning about all of this AN stuff. And, by the way, if somebody were to post a nice set of instructions for working with this stuff in the site's "how to" section, I and I'm sure others would be very grateful.

I wasn't sure which forum to post this in, but this seemed the most likely. Move it if you need to, Ron.

Eric

 

[Al Wohlstrom]

To all of you very knowledgeable folks:

If you're running braided hoses/AN fittings, how do you connect to something that has a plastic slip-on fitting? In this specific example, it is a Bosch pump and the inlet/outlet tubes are plastic with a bead clearly intended for a hose to slip on and be secured by a hose clamp. Is there even a way to do this, or do you just use hose clamps and hide the device so nobody can see the clamps?

I apologize, but I am very slowly learning about all of this AN stuff. And, by the way, if somebody were to post a nice set of instructions for working with this stuff in the site's "how to" section, I and I'm sure others would be very grateful.

I wasn't sure which forum to post this in, but this seemed the most likely. Move it if you need to, Ron.

Eric

Can you thread (NPT) the pump outlets to accept AN fittings? AN makes NPT to AN fittings.

 

[Julian]

Are you using AN fittings for aesthetic purposes or for security and piece of mind? If it's the latter your bets option is to ditch the Bosch pump and find one with a metal body and NPT/AN ports, otherwise it's always going to be a weak link.

If your not too concerned with the security aspect you can use a short section of hose to a barb to AN fitting or as suggested try and modify the pump, but personally I'd prefer not to tap NPT into plastic as the fitting will stress the plastic thread and body as it is tightened.

 

[Seymour Snerd]

To all of you very knowledgeable folks:

...if somebody were to post a nice set of instructions for working with this stuff in the site's "how to" section, I and I'm sure others would be very grateful.

The back of the Aeroquip catalog covers most of what you need to know about making up hoses and fastening torques, etc.:

http://hydraulics.eaton.com/products/pdfs/A-SPPE-MC001-E5_Catalog.pdf


There is also a video on hose assembly here:

YouTube - #6 Swivel Seal Assembly=

And then of course Carroll Smith's books "Engineer to Win" and "Carroll Smith's Nuts, Bolts, Fasteners and Plumbing Handbook".

 

[Alex]

I would advise against just band clamping an AN hose onto something, especially something involving fuel - i've tried it twice, had the hoses fail twice (once it failed in a few weeks, another it take several months). One failure was just a tube with a bead on it, another was a barbed tube.

 

[Dave]

I have used these a few times except in the blue / red not the polished

Spectre Performance 2268 - Spectre Performance Magna-Clamp Hose Clamps - Overview - SummitRacing.com

I have AN fittings one end and these on my fuel pump. Seem to seal ok and keep the AN look.

 

[Mark]

Whilst Albany's suggestion would work, my personal choice would echo Julian above. Ditch the Bosch unit and get a pump with a metal body and NPT/AN fittings.

 

[Eric]

Thanks for the responses.

I've also run across this:
JEGS Hard-Line AN Adapter Fittings - JEGS
It would be easy to cut off the bead from the inlet/outlet (shortening each by about 1/8") and then use this ferrule-type setup. Seems like this might be a solution.

Thoughts?

Eric

 

[Seymour Snerd]

I've also run across this:
JEGS Hard-Line AN Adapter Fittings - JEGS
It would be easy to cut off the bead from the inlet/outlet (shortening each by about 1/8") and then use this ferrule-type setup. Seems like this might be a solution.

Compression fittings in general depend on the enclosed tubing being of a rather precise specified outside diameter. Furthermore, these particular fittings are intended for aluminum tubing I believe, not plastic, although compression fittings for plastic are not unusual. I don't know, and I don't know how to reliably determine, if that compression fitting would be safe on your plastic tube.

You should probably also consider the effect of the weight, mass and stiffness of the hoses and fittings you are connecting to your plastic hose barb. It may not be designed to support that kind of hardware, as opposed to a typical street car's rubber or plastic hose.

Like some others, if it were my car I would use a fuel pump with interfaces designed for the intended application (eg AN plumbing). For example, the $75 Carter 4070 was recommended to me by Dennis Olthoff for use in my FE-engined GT40 Mk II.:

Carter P4070 Carter Competition Series Electric Fuel Pumps

I tend to be rather conservative in dealing with gasoline under pressure.

 

[Alex]

Thanks for the responses.

I've also run across this:
JEGS Hard-Line AN Adapter Fittings - JEGS
It would be easy to cut off the bead from the inlet/outlet (shortening each by about 1/8") and then use this ferrule-type setup. Seems like this might be a solution.

Thoughts?

Eric

I think that's a bad idea - it's meant for metal tubing.

It seems to me your best bet is to either replace the pump or use a piece of rubber hose on it that terminates into a custom welded up adapter - one end is bard'd, the other end has an AN fitting welded onto it, like this

 

[Eric]

Again, thanks for the responses. It's always good to get input from others. FYI, this application is for coolant, not fuel.

Eric

 

[Seymour Snerd]

Again, thanks for the responses. It's always good to get input from others. FYI, this application is for coolant, not fuel.

Eric

Oh! Don't know why I assumed it was a fuel pump. That changes things considerably since the fluid is not flammable and you have a reasonable chance of recovering from a failure.

Bosch makes a coolant pump? Can you provide details?

 

[Alex]

Again, thanks for the responses. It's always good to get input from others. FYI, this application is for coolant, not fuel.

Eric

I see. Here's what happens on a coolant line when you use an AN hose and clamp him onto a barb'd plastic fitting. (i'd imaigne similar to your pump)

Took about 10mths to fail. The above welded guy replaces this piece.

 

[Eric]

...Bosch makes a coolant pump? Can you provide details?

Alan

It's actually an intercooler pump. Here's the data sheet from Bosch.

Eric

 

[Eric]

Alex

Why do you think that failure occurred? It seems to me that unless you overtightened it, the plastic should not have collapsed by that much. Curious.

Eric

 

[Seymour Snerd]

Eric --

I see the Bosch hose barb is dimensioned at 19mm, which is only 0.002" smaller than 3/4". I'd sure be tempted to try a 3/4" compression fitting on there, but going easy on tightening it (relative to whatever they recommend for aluminum).

Or, McMaster has a compression to FNPT adapter made of brass designed for 3/4" nylon tube: part #50915K234. ($33). The male NPT version is about 1/3 as much money. Apparently the difference is they use a plastic sleeve. Then you could from that brass NPT to whatever AN you want.

And of course McMaster doesn't mfr. this stuff, so if you can figure out who made it (like Parker or Swagelok) you might find that they make a plastic compression to 37-degree flare fitting so you could do it all in one step.

Like you I don't understand the way Alex's hose barb failed. It's almost as if it expanded and then folded into itself.

 

[Alex]

Like you I don't understand the way Alex's hose barb failed. It's almost as if it expanded and then folded into itself.

No clue - maybe the heat (coolant) caused it to slowly expand/contract/expand/contract and it just failed?

Or maybe it has something to do w/ the fact aeroquip says NOT to hose clamp their braided AN hoses onto a carb (can cause hose failure ... but doesn't explain barb failure)

Oh well, in any event I won't be doing that again.

It worked for about 8mths, then for 2mths I got a very tiny drip (no clue where it was coming from). Then one day that drip turned into a spray of coolant anytime the system was pressurized (i.e., engine running)

 

[Howard Jones]

I think I would treat the complete hose assembly as if it had plastic on both ends. What I mean by that is a tipical steel braided hose is very stiff and not intended to be attached to a fragile plastic fitting. I would ude a quaility rubber hose of the correct size and a quailty band clamp on each end and be done with it.

This will allow the hose to flex and asborbe movement without transfering the stresses to the plastic fitting.

 

[Eric]

I see the Bosch hose barb is dimensioned at 19mm, which is only 0.002" smaller than 3/4". I'd sure be tempted to try a 3/4" compression fitting on there...

Alan

That's what I'm thinking. Pressure will be in the 12 to 16 psi range. Very tempting to try (even if Alex will yell at me).

By the way, I'm using braided nylon hose instead of braided stainless steel hose. I don't know if it is more forgiving or not as far as flex.

Eric

 

[Alex]

Alan

That's what I'm thinking. Pressure will be in the 12 to 16 psi range. Very tempting to try (even if Alex will yell at me).

By the way, I'm using braided nylon hose instead of braided stainless steel hose. I don't know if it is more forgiving or not as far as flex.

Eric

hehe

I still think your best bet, if you are determined to use the pump, is to start off with a piece of regular rubber hose that is meant to be clamped on then terminate it into a custom AN/barb'd fitting like I posted above. Then from there run your AN hose. It is a tad bit more onerous (because you have to make the fitting) but I think that's worth it for peace of mind.