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Do I need a flex line?

Do I need a flex line?

Do I need a flex line?

My back-up pump came in today.

My primary lift power unit (still waiting on a few valves for this) is mounted in a room right behind my lift (this will keep the noise, any oil, the two batteries and such in the utility room).

I want to mount the back-up unit right beside the lift (with some luck I will only use it every three months or so to test it ... always want to know if it will work when you need it).

Then I started thinking (dangerous) .... when I mount the back-up power unit (vertical power unit off a two post auto lift) do I will not need a flex house? For that matter, when I mount the main power unit do I need a flex?

Every unit I have ever worked on had a flex hose on it, but that is because every unit had a cylinder had had to move (snow plow, log splitter that changed from vertical to horizontal, ....). I worked on a cheap Chinese tow behind back hoe that was completely plumbed with flex hose. I am sure this was done because it is much easier for an unskilled laborer to rout a hose than tubing but I have a good quality tubing bender and don't mind taking the time to bend and mount tubing.

I did some reading and the only reason given to use a flex was 1) movement 2) noise reduction

The article seemed to suggest that flex hoses were actually a week point in the system as they can wear out or deteriorate over time.

So, do I need a flex hose?

Thanks so much again for all the help and advice!!!!!!


RE: Do I need a flex line?


Hoses are, as you say, a poor alternative for rigid pipework, but also necessary where there is movement that needs to be allowed for.

If there is relative movement between the units the you need to connect, then use hoses, but keep them as short as possible as they do have higher pressure drop than rigid pipework.

The noise attenuation benefits of hoses are often overstated. If they are really working to remove noise, then they will be absorbing energy and they therefore wear out.

Hoses are not exactly the weak point in a system as most hose factor of safety ratings are 4:1, so they rarely fail. None the less, they are not to be used as a convenient replacement for rigid pipe work.

If you are able to use rigid tube, then my advice would be to do so. By all means use a hose as appropriate, but be aware of the limitations that hoses have.

Good luck


RE: Do I need a flex line?

Thanks ...

In my case, as the pump is permanently mounted and the lift if permanently mounted (and as I stated in earlier posts, there should be minimal temperature rise so I should not need to worry about expansion in the tubing), I will plumb everything with rigid tubing.

You guys (and a lot of reading on the web) have taught me a lot over the last few months.

In order to make the most reliable system possible and to eliminate as much restriction as possible, I am planning to use bent tubing and not fittings where possible.

I am also trying to use SAE (o-ring) fittings on all the new parts I order. Unfortunately the cylinder and pump being 30 years old have NPT ports on them.

Thanks again ...... Mike

RE: Do I need a flex line?

You can adapt NPTF to SAE straight thread. It does add another fitting.


RE: Do I need a flex line?

Exactly what I am going to do! I just put up a post asking about NPT sealant. I want to change the NPT to SAE right at the device if possible. If I need to do any work, I can take things apart at the SAE connections and not touch the NPT connections.

Funny, I do the same thing when I work on a house with aluminum wire (we did this up in Canada back in the 70's) ... and had a lot of houses burn down.

I take every connection and pigtail a new piece of copper off them. I use approved high pressure connectors and "no-ox" the connections. This way all I have to work with in the future is new copper wire .... not the original aluminum wire.

If it was up to me, I would just rewire the house but I have had a few family member who didn't want to spend the money or time so this is a good way of making the house "safe".

Thanks so much again!!!!!!!!!!!


RE: Do I need a flex line?

If there is some relative motion between the hard line and the device it connects to, then a flexible section of tube/hose is needed to provide strain relief.

The most important consideration is minimizing the potential for leaks in the circuit, and in this regard fewer joints is usually better. Both metal tube and flex hose can work well and provide good service life if the installation is designed properly. NPT connections are a poor choice if reliability is a concern.

RE: Do I need a flex line?

"If they are really working to remove noise, then they will be absorbing energy and they therefore wear out."
There is a difference between "removing noise" and isolating noise by preventing power unit vibrations transferring along rigid pipework to other components. A "spring" will perform this function without absorbing any energy.

je suis charlie

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