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.