Braided flex hose maximum allowable air velocity 1

[pegus]

Good day,

I was recently working with a 6in flex hose component (as shown in the link), it will work with compressed air at 650F, 80psig and a flow of 380 ft/s.

https://www.metraflex.com/product_cat/flexible-metal-hose/

I read that when the air flows over 150 ft/s, they place an inner liner to prevent the inner bellow excessive vibration and a possible failure.

But I wonder how high the flow can gets with this interlock liner? I asked the provider but couldn't get an exact answer, he gave me reference info.

Regards,

P.P.

 

[GregLocock]

"he gave me reference info" which you have read. What did that say?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[TugboatEng]

OP is asking a complicated question. The reference literature says 150 ft/s as a max without a flow liner. The literature likely doesn't reference a maximum velocity with a flow liner. I've had plenty of flow liners crack on the flange end so the tubes do fail. I don't know what my velocity was but I believe the failures had another cause.

 

[pegus]

Thanks GregLocock,

Regarding the reference info, is that they know the same type of flex hoses have work with air flow at 280 ft/s.

Regards,

P.P.

 

[EdStainless]

I have done failure analysis of a few of these, SCC or fatigue failures of both liners and bellows.
By the time that you get multi ply over braid and a liner these 'hoses' are only vaguely flexible.

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P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

Your link points to several different items - which one did you mean?

I doubt there is a defined limit, but those sorts of velocities are getting silly for a braided hose. Any particulate matter at all and you'll wear out anything in no time at all, especially at that sort of temperature. As for the pressure drop, well that's going to be not insignificant

What is this? A rocket engine or something?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

That's actually in the territory of a diesel engine exhaust. I crunched the numbers a while back for an 16 inch exhaust and got 9000+ fpm in the stack . That same mass flow passes through two 4 inch metal bellows on the turbocharger inlet. I don't know what the pressure ratio is there so I don't know the volume rate to calculate velocity.

We did operate a bellows at 150 fps for some time. Someone forgot to order the liner (me).

 

[pegus]

Thanks for the reply LittleInch,

This is for an engine exhaust testing.

Talking to a peer, he mentioned that a rule of thumb up is to not exceed 0.3 Mach. I checked the Mach number for this application and we will be around .2.

Most braided flex hose providers mention that above 150 ft/s is recommended to install a liner to protect the bellows from high vibrations, but I can not find data of velocity limit of these liners.

I hope this information helped to understand more the concern,

Regards,

P.P.