Rubber hose life? Silicone hoses?

Hi Sean,

I do use the spring clamps on the 17mm coolant hoses. I should have made my post more clear. I was referring more to the fuel hose, the oil hoses and the 25mm (1") coolant hoses.  I didn't mention these because these come from Rotax already on the engine for the 17mm coolant hose (not the for the 25mm hose). Plus if you using these spring clamps then use of the proper hose is important. 

Hi all

The constant pressure clamps are standard automotive technology.  Rotax used to use screw clamps but the problem with those, execiay on cooling hoses, the rubber over time will off gas and this leads to shrinkage of the line.  This translates into leakage. 

Here is the text from one of the GATES hose websites about replacement.  it is not about aviation which we generally want to replace before problems, as Roger points out it is preventative maintenance.   

"When to replace coolant hoses

When inspecting cooling system hoses, a four-year replacement cycle is the basic rule of thumb, but is by no means precise. Vehicles operating under severe conditions or vehicles that are not driven often may require more frequent replacements. Therefore, it is imperative to periodically inspect hoses – even hoses less than four years old – for damage from the major hose enemies electrochemical degradation, leakage, heat, ozone, abrasion, and oil contamination whenever a vehicle comes in for service.

It should be noted that the number one cause of cooling system hose failure is electrochemical degradation. This is an electrochemical attack from the inside of the hose. It is impossible to detect this from a visual inspection of the hose. In our problem diagnosis section of this site you can read all about how to detect electrochemical degradation and how to prevent it.  "

Cheers

Hello friends,

the subject of hoses and hose clamps is getting more and more exiting!

The constant tension springs (CTS) are used because they are cheap and quick to fit. If no high demands are placed on the clamp, they are OK. Rotax already knows when such clamps can be used. The screw clamps (fuel injetion clamps and similars) can still be old technology. They were good and will always be good. For me there is no point in philosophizing about which clamps are better.

I actually meant the crimp clamps, which I replace with screw clamps. The CTS are OK. When Rotax assembles an engine (I was recently in the production at Rotax / Austria),  or a new engine is installed you can mounten from all sides. But it is not always easy to reach the hose clamps when the engine is fully installed at the airplane. If you then need pliers to loosen a CTS, it can sometimes be difficult or even impossible.

There was no problem with the hose clamps in the past, nor is there a problem today. CTS have to fit exactly, who has a whole portfolio of sizes in their workshop? Maybe a commercial company, a DIY mechanic like me uses the old clamps if they are still good, or makes do with screw clamps.

Of course, the ID of the hose must be slightly smaller than the OD of the tube. But what if it fits exactly? What do you do then? A clamp is not just there to prevent the hose from slipping down on its own. The clamp must clamp and seal.

50 years ago, when I was still a child, my father and others often had problems with the cooling water hose. That was yesterday. A lot has happened in the material sector for hoses in particular (at quality manufacturers). Today I drive my 20-year-old Mercedes and I'm not interested in hoses. I only go to the garage to change the gearbox oil and when something is broken. I can't remember anything about hoses. Maybe the mechanist will replaced some.

I take a closer look at my airplane, but I have never heard of hoses having to be replaced after 4 years. Either the company has its production in China or it wants to deny any liability. I am skeptical when a manufacturer writes something, he wants to sell and assume no liability. I do understand something about chemical relationships, but I think this is totally exaggerated.

For my understanding the topic has completely slipped away. Who dares to say how long hoses usually last? Just report your experiences. I'm sure there were some people like me who unknowingly flew with outdated tubes/hoses and only found out afterwards. Are there serious problems with hoses and hose clamps (installation errors do not count)?

It's not about disregarding regulations. Do what the manufacturer / authorities wants. The only question is how long hoses can normally be used without falling out of the sky.

Greetings - have a nice flight

Hi Roger

"I do use the spring clamps on the 17mm coolant hoses. I should have made my post more clear. I was referring more to the fuel hose, the oil hoses and the 25mm (1") coolant hoses.  I didn't mention these because these come from Rotax already on the engine for the 17mm coolant hose (not the for the 25mm hose). Plus if you using these spring clamps then use of the proper hose is important. "

Can't explain why,  I have always enjoyed the hose & clamp topic (weird! I know).

On my new (now124.9hr) 912ULS I have the original Rotax constant tension spring (CTS) clamps and automotive/aftermarket ones on my coolant radiator (25mm). So far so good.

Gates supply all of my hoses (exception being the little bent 17mm one on top of the engine) and they all fit (ID) perfectly, so the clamps are more for security than leak prevention.

Hi HKK

"The constant tension springs (CTS) are used because they are cheap and quick to fit. If no high demands are placed on the clamp, they are OK. Rotax already knows when such clamps can be used. The screw clamps (fuel injetion clamps and similars) can still be old technology. They were good and will always be good. For me there is no point in philosophizing about which clamps are better."

I actually think the CTS clamps are better than the screw clamps (for cooling systems). 

They are not particularly cheap (to me) but as you say quick to install/remove with the right tool/technique.

Unlike the screw clamp, the CTS can not be over tightened - a very common problem

They provide a constant 360 degree pressure, that is unaffected by engine heat/cooling cycles

Can, like the screw, be reused many times.

So far I only use them on the cooling system - my oil/fuel hoses are all secured with fuel injection type clamps.

Hose quality, correct fit, spigot/barb type (don't use the old multi toothed/serrated type) and clamp all work together. Done right there will be no leaks.

There is nothing wrong with "old technology" but when something better comes along you have the option to use it or not.

( I had a thing for MB W123's / 300D, had seven at one stage, one was a factory 5 speed manual, all gone now, sad!)😈