What kind of hydraulic flow restrictors do I need?

[Jim Miller]

Thanks J_J! I'm printing out the picture you posted and I will also take the hose connector that this restrictor will screw into so I'll have the exact treads. We have a local Tractor Supply as well as several shops that make hydraulic hoses and stock "some" fittings. Maybe I can get really lucky and find these restrictors locally!! I'll be sure and post what I find and how this turns out. It's a shame when folks don't ever let you know how the problem gets resolved.

 

[AVFDmedic]

Old thread, but really helpful to me, as I had the same concern with my new bucket grapple. Took the advice and installed a pinhole flow reducer (Tractor Supply....$5.49) in one line only. Yes, it did settle the grapple down - in both directions. I did need to enlarge the hole slightly. Thanks for the help!

 

[S854]

No sense in letting a good thread wither on the vine… bumped once in 2010… again in 2013… AGAIN in 2017… now here we are running headlong at 2023, time to revisit an, IMHO, excellent thread…

reading through the posts, brain surgery or not, provided the information and reasoning I was looking for to (hopefullyj correct a hydraulic issue I’m experiencing…

although I’m using the info for a runaway 3-point top link (which operates smoothly when not connected to a load)… when I tilt my box blade down, I get considerable chatter from the hydraulics… reversing the flow to tilt it back up results in smooth, albeit rather rapid movement…

Using the logic provided in this thread, and the space constraints imposed by my CUT, I’ve decided to place a singe orifice flow restrictor on the rod end of my top link… if I read, and understood, this thread correctly… the weight of the BB is pulling on the top link faster than the fluid can be supplied… causing the chatter… placing a restrictor in the BASE side supply line will further exacerbate the chattering… a side benefit to the chatter remediation would be the tilt angle will slow down…

SO… did I read and apply all this info correctly?

 

[MechanicalGuy]

Hydraulics typically restrict supply of fluid, pneumatics the exit of the fluid (gas).

This is due to the compression of gas and the stiction of the cylinder in an air or pneumatic situation.

Flow is typically restricted in one direction and free flowed in the other direction on commonly available restrictors.

I can't believe that your grapple moves too fast that you are having to install restrictions.

 

[NewmanGrove]

Great thread.. I will add my 2 cents. Cavitation can be a big problem, not only in the pump area, but also in the hydraulic lines. I have a CAT 216B skid steer with a grapple that keeps blowing a tiny hole in the 5000 psi hydraulic hose about 3 inches from a pin hole flow restrictor. The restrictor is located in the line that goes (to/from) the rod side of the cylinder. The hose will fail if I continue to supply pressure to open the grapple after it is fully open. I mean, all of this fluid and pressure is going to the rod side of the cylinder. I suspect a cavitation bubble is being compressed by the full pressure and then explodes when I stop applying the hydraulic pressure, and it rips a tiny hole in the inside rubber of the Hydraulic hose. I'm drilling out the flow restrictor from .062 to .120 to see if this helps. It might make it worse.

 

[ruffdog]

Great thread.. I will add my 2 cents. Cavitation can be a big problem, not only in the pump area, but also in the hydraulic lines. I have a CAT 216B skid steer with a grapple that keeps blowing a tiny hole in the 5000 psi hydraulic hose about 3 inches from a pin hole flow restrictor. The restrictor is located in the line that goes (to/from) the rod side of the cylinder. The hose will fail if I continue to supply pressure to open the grapple after it is fully open. I mean, all of this fluid and pressure is going to the rod side of the cylinder. I suspect a cavitation bubble is being compressed by the full pressure and then explodes when I stop applying the hydraulic pressure, and it rips a tiny hole in the inside rubber of the Hydraulic hose. I'm drilling out the flow restrictor from .062 to .120 to see if this helps. It might make it worse.

Is there any way you can put the restrictor on the other side of the cylinder (non rod end)? Restricting on the rod end allows the piston end (more sq in surface) to put more pressure (amplify) on the restrictor. Also, if there is an elbow or bend near the restrictor orifice, it may cause erosion of pipe or hose.

 

[kennyd]

Wow, old thread!

We offer a lot of different restrictors now, and will be carrying more styles soon:

Hydraulic Parts - BoltOnHooks LLC

Bolt-On Hooks and Hydraulic accessories for compact tractors.

www.boltonhooks.com

 

[NewmanGrove]

Is there any way you can put the restrictor on the other side of the cylinder (non rod end)? Restricting on the rod end allows the piston end (more sq in surface) to put more pressure (amplify) on the restrictor. Also, if there is an elbow or bend near the restrictor orifice, it may cause erosion of pipe or hose.

Thanks for the suggestion. There is no bend or elbow in the area that keeps developing the leak. The hose is almost straight in that location, but you are correct that that the amplified pressure is causing the erosion and cavitation. I have drilled the orifice out to .120 and the new hose is holding up so far. Below is something I copies from the internet that shows the cavitation down stream from the flow restrictor. I'm still having trouble wrapping my mind around the conflicting views of Amplified Pressure, and the Reduction in pressure from Bernoulli's principle.
NEUTRIUM.. Cavitation in Restriction Orifices and Valves..
In the case of a simple concentric restriction orifice the fluid is accelerated as it passes through the orifice, reaching the maximum velocity a short distance downstream of the orifice itself (the Vena Contracta). The increase in velocity comes at the expense of fluid pressure resulting in low pressures in the Vena Contracta. Downstream of the Vena Contracta in the recovery zone, the fluid decelerates converting excess kinetic energy into pressure energy as it slows. Therefore the intermediate pressure in the Vena Contracta is lower than the final system pressure and thus the highest chance of experiencing cavitation as demonstrated in the figures below.