Hyd hose diameter

[jake98]

How does the diameter/length of a hose affect a hydraulic cylinder's performance? I'm planning on using some long thin hoses on a 4"x34" cylinder and was wondering if it makes a difference..

 

[AKKAMAAN]

How does the diameter/length of a hose affect a hydraulic cylinder's performance? I'm planning on using some long thin hoses on a 4"x34" cylinder and was wondering if it makes a difference..

In a Constant Flow system, CF, (fixed displacement pump), smaller size crate more pressure and flow will stay the same till Pressure Relief Valve, PRV, opens, or flow get diverted while feathering the Control Valve, CV.

In a Constant Pressure system, CP, (variable displacement pump), smaller size hoses will reduce flow.

In both systems, smaller size hoses will cause a pressure drop during flow, and that pressure drop will make a loss of power into HEAT. In other words, smaller size hoses ALWAYS causes inefficiency and excessive HEAT.

What flow are you planning to run through this hose?
What size of hose are you planning to use?

You can find hose size by using a Nomogram, from Parker Hydraulics, like this

or using my online spread sheet like this

This spread sheet is based on the Parker Nomogram recommendations

 

[jake98]

Thanks.
So, basically, the full pressure is gonna get there eventually, one way or the other, right? I'm talking about 30' hoses.

 

[J_J]

AKKAMAAN,

Is there a large difference between say a 1/4 in hose, 3/8 in hose and a 1/2 in hose to extend a cylinder?

Are we talking about time and heat?

 

[J_J]

Thanks.
So, basically, the full pressure is gonna get there eventually, one way or the other, right? I'm talking about 30' hoses.

The pressure is developed by the end product on the end of the hose, be it a cyl, or motor.

 

[Chilly807]

In my experience, which is limited, you need at least as large a hose as you already have on the tractor for the supply to the valve which controls the implement.

As an example, if you have 1/2 inch hoses everywhere else, you need at least 1/2 inch for the new cylinder.

For a 30 foot run, you may want to consider larger cylinder hoses in view of the added friction. You'll probably be ok with 1/2 inch in this example (cylinder as opposed to a motor), but definitely don't go any smaller than what you already have.

If the cylinder will see limited use, you can get away with smaller hoses, but it's not good practice.

Sean

 

[AKKAMAAN]

Thanks.
So, basically, the full pressure is gonna get there eventually, one way or the other, right? I'm talking about 30' hoses.

Yes....but lets say the load on cylinder itself takes 1000psi of pressure to move at 17.14 gpm pump flow, the power required to move the cylinder will be
>> 1000x17.14/1714=10hp
if the resistance in the hose creates a pressure drop of 500psi, that will add another 5hp to move the cylinder, it will show that that extra load will labor the motor/engine more, to a total of 10+5=15hp and a pump pressure of 1500psi.

If but rpm drops due to this extra resistance from the hose....well then you can say the hose "reduce the flow"....

As long there is flow, there is always some amount of pressure drop through the lines, fittings, ports and valves. By up sizing components we can reduce the fluid velocity and the pressure drop.

Note that the lenght of hose will become a larger factor when they are that long as 30', so that will probably push you to choose another 1-2 sizes bigger, to reduce pressure drop.

But this pressure drop do not necessary have to be a great bother, if your prime mover have enough power, and your cycling is more intermittent than continuous. But if it causes PRV open then you have a real problem.

EDIT:Another very important thing is the return flow from the capped side when retracting the cylinder, it will always be significantly larger than the pump flow. That flow have to be the nomogram INPUT when calculating hose size.
2nd EDIT:Example. Pump flow 10gpm and we use a 4:3 ratio DA cylinder (4"bore and 2"rod, or 5" bore and 2.5" rod etc), "return to tank" flow from capped side when retracting, will be 4/3x10gpm=13.33gpm

 

[AKKAMAAN]

AKKAMAAN,

Is there a large difference between say a 1/4 in hose, 3/8 in hose and a 1/2 in hose to extend a cylinder?

Are we talking about time and heat?

All three will extend the cylinder at full speed as long as prime mover keeps up rpm and PRV do not open.....the difference is the extra power/fuel that have to used for the smaller hose option. The extra fuel is burnt to create heat.

 

[AKKAMAAN]

The pressure is developed by the end product on the end of the hose, be it a cyl, or motor.

It is not only the "end product" the resist to the flow.

We have discussed this before, and I get back to it!

If we push an object with a solid piece of material (steel bar or 2x4 lumber), the tension aka pressure is caused by the prime mower, AGREE! The object moves because we have applied a FORCE larger than the opposing RESISTANCE.

Now when we talk hydraulic all suddenly it is the object that causes pressure.

IMO, the proper way to look at what causes pressure is that PRESSURE IS CAUSED by the source of FORCE, which is the prime mover (torque)

 

[jake98]

for my application heat or speed isn't an issue, just that it makes the full power. thanks for the info. Happy Thanksgiving.

 

[kennyd]

Smaller hoses are fine between the valve and the cylinder since they are not continuously flowing fluid. They can also help keep the cylinder speed slower for better control. 1/4" hoses for example work great on TnT setups.

What is this cylinder controlling, and what size is the pump?

 

[jake98]

Under pump capacity in the manual it says:
Max. flow rate 12.9/ 1st: 8.3, 2nd: 4.5
So I guess that means two pumps?

I'm going to chain the cylinder between stumps and see if I can pull some out.

 

[Chilly807]

The larger number is the main pump for general hydraulics, usually the smaller number is devoted to power steering only.

Sean

 

[kennyd]

1/4" hose sounds perfect for your project: It's cheaper, lighter, easier to store.

 

[AKKAMAAN]

AKKAMAAN,

Is there a large difference between say a 1/4 in hose, 3/8 in hose and a 1/2 in hose to extend a cylinder?

Are we talking about time and heat?

Time basically the same as long as PRV is closed, heat differs, engine labor too

 

[J_J]

Time basically the same as long as PRV is closed, heat differs, engine labor too

The original post by jake98 wanted to know if the size and length of the hose made a significance difference. So, your answer is no, is that right. I think the reason he was asking is because of cost. However I haven't seen a lot of 4 in cyl use 1/4 hose.

 

[AKKAMAAN]

The original post by jake98 wanted to know if the size and length of the hose made a significance difference. So, your answer is no, is that right. I think the reason he was asking is because of cost. However I haven't seen a lot of 4 in cyl use 1/4 hose.

jake98 did NOT use "significance" in his post, that is your own interpretation...:laughing:
OP asked

if it makes a difference..

...and I try to explain the difference....

Obviously it depends on what values one put in the phrase "significance difference". Some posters seems to think any hydraulic design is OK as long as PRV is closed during operation....:confused2:

Choosing the "right" size hose, is most of the time a negotiation between the investment budget and the operation cost (fuel) budget. Especially when an up size force you to choose 4 wire instead of 2 wire due to pressure rating. 1/4" is cheap, and many times you can get away with 1 wire hose (up to 2750psi)

I would love to see Bill (wdchyd) or someone else with a "shop", to set up his pump and flow meter test rig, and push 0-20 gpm through a 10ft long 1/4" hose with 2 straight fittings. Same test with a 20ft hose to determine the impact of length. Same test with 1/2"x10ft to determine impact of size. Pressure gauge T'd in front of the hose and the other end into the the tank fill hole. Document oil viscosity grade and operating oil temperature. That video documentation would show the truth!

With a 1/4" hose, I guess somewhere between 250-500psi pressure at 12 gpm...

power loss??
12x250/1714=1.75hp
12x500/1714=3.5hp


We are talking heat power like a furnace....

A 1/2" has 4 times larger cross section area than 1/4".

if it makes a difference..???

Does it?

 

[J_J]

Your numbers are probably right, but like you said, if the HP is there,and there is sufficient cooling of the fluid, then what. It comes down to expense. I would also like to see the test, using different hoses, pressure and volumes. I had thought you had the hyd simulation software that you could plug in the components. I appreciate your knowledge and assistance in helping us all, understanding hydraulics.

 

[glastron23]

Hi guy's AKKAMAAN we have some 55 foot bucket trucks that had a similar problem, we were experiencing very high return back pressures at the bucket (450 to 600 psi) that was interfering with same of the hand held hydraulic tools they using, the trucks were using 5 gpm OC pumps with throttle advance for 7 gpm. From the pump through the boom to the bucket controls and then back to tank we had about 165 feet of #8, 518c plastic hose ( if you want a light,some what of a tight radius,corrosion proof,cheap hose check it out) . the pressure and return were both #8, to resolve the high back pressure we had to install a second #8 return line from the bucket controls to the tank. this dropped the back pressures to 225/275 psi. as far as the flow, rates the were the same in both. Jim

 

[AKKAMAAN]

Your numbers are probably right, but like you said, if the HP is there,and there is sufficient cooling of the fluid, then what. It comes down to expense. I would also like to see the test, using different hoses, pressure and volumes. I had thought you had the hyd simulation software that you could plug in the components. I appreciate your knowledge and assistance in helping us all, understanding hydraulics.

Thx J_J!
I have been looking into HYD SIM SOFTWARE, but they are still not the "real" thing....
I used to have a "sorta complete" education lab at the school I worked for till year of 2000........

I know there are some online calculators for pressure drop, but they will always be questioned too....and I don't trust them when I can't track the formula programming....this Gates pressure drop calculator shows this result for a 1/4" 10ft hose...see the jump in numbers compared to 3/8" and 3/16"

AutomationStudio is the ultimate simulation software, but so expensive...