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Anonymous Poster

Hydraulic Hose Sizing

06/20/2009 11:39 AM

Hi,

I am specing out a hose ( Suction line) for one of my pumps. The suction flow is about 15 gpm. I do understand that the thumb of rule is that the hose size should be big enough such that the speed does not exceed 4 ft/s. In order to achieve that, i need to have a hose size that should be at least 1/1/4 inch diameter. The suction port on the pump is 3/4 inch opening. Currently the port on the reservoir tank is 1 inch. My question is

1) Should i use some adapters to increase the port size on the pump, so that i can fit a 1/1/4 inch hose? By doing this, the flow through the pump would still exceed 4 ft/s. Is it alright to do that?

2) Should i go with a 1/1/4 inch port on the reservoir? Would it help in any way? or it doesnt really matter, since there is still a restriction on the pump side. Thank you.
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tcmtech
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8376
Good Answers: 775
#1

Re: Hydraulic Hose Sizing

06/20/2009 1:34 PM

It would depend on how far your sucking the fluid, the coldest operating tempurature and the viscosity of the fluid as well.

I have ran 20 GPM pumps with an 18 inch lift on 5 feet of 1 inch line with no cavitation problems even at starting tempuratures of -15 F.

Ideally the 1 1/4" should be used but thats more of a suggestion than a law. If its a short run 1 inch will work fine.
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vanuta
Commentator

Join Date: Jun 2009
Posts: 88
#2
In reply to #1

Re: Hydraulic Hose Sizing

06/20/2009 2:14 PM

Is the hose selection, to protect the pump or is it to protect the hose itself? or both?
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2
BudT
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Join Date: Mar 2007
Location: Newburgh, IN
Posts: 283
Good Answers: 10
#3

Re: Hydraulic Hose Sizing

06/20/2009 2:29 PM

If it was my system I would go with te 1.25 Port and SUCTION HOSE and reduce it down at the pump.

That way the Flow Velocity is within the range desired fro Suction Lines and only the short section at the Pump Inlet is undersized.

The 1.25 line will eliminate cavitation and increase pump life.

Be sure to use Hose Rated for Suction and keep it as short as possible.

There is only ONE ATMOSPHERE of PRESSURE, at Sea Level, to push the Oil through the Suction Line so it is limited.

A pressure line can be udersized since the pump will just increase pressure to force oil through it. NOT A GOOD PRACTICE SINCE ANY PRESSURE DROP IN A CIRCUIT REDUCES THE AMOUNT OF WORK AT THE ACTUATOR and CAUSES THE ENERGY LOSS from the PRESSURE DROP TO PRODUCE HEAT.

It's a One Time Deal to make the Suction Line right but can be a long time problem if done wrong.

You can read my full take on Plumbing in a book I use to teach Basic Fluid Power here: http://www.hydraulicspneumatics.com/200/eBooks/ Look in Ch. 3, pages 4-5.

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Tim in Mexico
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Join Date: Jul 2008
Location: Anywhere I may be at the time
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#4
In reply to #3

Re: Hydraulic Hose Sizing

06/21/2009 11:20 AM

GA...
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Oliver Dunthorne
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Join Date: Nov 2008
Posts: 116
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#5

Re: Hydraulic Hose Sizing

06/21/2009 1:23 PM

Hi,

You should stick to the old rule of thumb. 1 m/sec for suction, 3 m/sec for return and 5/7 m/sec for pressure. 5 m/sec for pressures below 200bar and 7m/sec above 200 bar.

You should not have the pump suction which requires a lift of more than six inches and preferablly a postive head of oil is always benefical. Distance is an other factor and long runs are to be avoided (try to keep it at less than 6/8 feet. Temperature is a factor or rather viscosity, the two are related. If you have heavy fluid, above 60 cst and are starting at below zero centigrade then increase the size of the pipe. Always avoid sharp bends etc.

I have an Excel spread sheet which enables you to slot in various parameters to give you power required, flows, pipe diameters etc. I would be happy to forward it to you but I don't know how to acheive this as I cannot see how to do an attachment with this reply.

If you can contact the editors of this site and forward your E mail address i would gladly send it to you.

Regards

Oliver Dunthorne

Hydraulic engineer
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vanuta
Commentator

Join Date: Jun 2009
Posts: 88
#6
In reply to #5

Re: Hydraulic Hose Sizing

06/21/2009 8:48 PM

Hi,

Thank you very much, you can mail it to me at the following E-mail address:

vanforum0407@gmail.com

I do very much appreciate ur help.
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GreyeTech
Member

Join Date: May 2009
Posts: 7
#7

Re: Hydraulic Hose Sizing

06/24/2009 2:06 PM

A general rule with hydraulic pumps is the inlet and outlet pump port sizes are speced by the manufacturer to suit the inlet velocity of 0.5 - 1.5m/s therefore based on your info that the pump inlet port size is 3/4" ( 19mm ) and a maximum velocity of 1.5m/s to ensure that no cavitation occurs, by calculation the pump displacement is about 25.5lts/min this would tie in with manufacturers specifications.

velocity in m/s = L/s x 1273.2/d* we have Vmax is 1.5m/s, d is 19mm( 3/4" )

therfore Pump flow = 19* x 1.5/1273.2 = 0.425l/s x 60 = 25.5l/min.

hope this is helpful
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Users who posted comments:

BudT (1); GreyeTech (1); Oliver Dunthorne (1); tcmtech (1); Tim in Mexico (1); vanuta (2)

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