I have a cat backhoe I recently acquired. My first piece of equipment tbh. After a few days of use, I lost the right steering. I couldnt find anything that explained anything as thorough as your video. I wish I saw it before I paid an arm to have dealer service come out for a diagnosis and a leg for them to get me to replace the orbitrol on my own which didn't fix anything. ( the new one actually goes right slower than the older one and will kick back a bit). Your video gave me a couple new avenues to look into and it should save me the last 3 limbs i have 😅.
Thanks buddy for this insightful tutorial ,its actually a good pointer for one project i am working on .i haev got a CAT forklift DP40KL , which has a stiff steering problem which started after the hoist contol valve was changed and i presume there is indeed something wrong with the circuitry and most probably the hydraulic pump could be a FDP and no priority valve in the circuit .
EXCELLENT video but I hoping for a troubleshooting section for priority valves because Ive been having an issue I cant figure out on my Allmand TLB. Maybe you can steer(/pun) me in the right direction. Im here because I think Ive narrowed it down to the priority valve but want some reassurance before I break into it. The machine starts fine and runs fine. The minute I touch the orbitrol steering wheel the engine bogs down hard and all other TLB functions slow to a crawl and it stays that way until I actuate the loader valve in anyway. Then the engine picks up and full function is restored until I touch the steering wheel in anyway again and I have to repeat the process. The hydraulic fluid also seems to get really hot after some use. So far Ive had the steering hydraulic cylinder rebuilt. It was leaking and it started a slow leak again right after rebuild. I checked all the orbitrol lines for blockage. I tore apart the orbitrol to look for problems. Looked clean. The only thing I think I have left to check is the load-sensing priority valve on the pump itself. Its an Eaton Series 26 Single Gear. Its referred to in the Eaton manuals as a load-sensing priority valve and the description of it mentions that "the excess flow(EF) is available for auxiliary circuits". Could the issue be related to the priority valve or the loader valve or either/both? Which should I attack first?
Hi it's quite more understanding , thank you sir , I have question or doubt , what is the consequences if the priority valve load sense relief is blocked by debris or the port is blocked manually ??
In the Alberta Apprenticeship books, they show an HMU from a CAT scraper with just 3 hoses hooked up and the bottom left port plugged. All the 3 hoses could be a 3/4 ID and run from the HMU under the cab floor through the frame. The top left port has a sort of nipple. I have no idea why it's set up like that. The bad thing is that I'm studying on my own and don't know anybody with that king of expertise... Anyway great video
Interesting they would choose a scraper. Cat scrapers i worked on had a very unique steering system with a follow up cylinder that sort continually re-entered the system. I'd have to dig into it.. been years. Are there that many Cat scrapers in Alberta? Scrapers are nearly extinct in eastern Canada. Replaced by 6wd trucks and mass excavators. Something that specific to one family of machine from one manufacturer should not be in apprentice curriculum imo
The bigger units like a 657 very likely use flow amplifier steering where the HMU is only controlling pilot oil to a remote valve that handles large volume flow to the steering cylinders
@@hydraulics There are hundreds of scrapers (20 years old or brand new) especially in Calgary and Edmonton to build roads outside the city and level new subdivisions, many gravel pits use them to strip the overburden. Recently there are buggy scrapers hooked up to rock trucks like CAT 740 or Volvo AD 40: they remove the box and connect the scraper hitch onto a fifth wheel on top of the rear truck frame. The company making this buggies is called KTec. I'm studying for my Red Seal and there is a pile of stuff to review... Thanks for your interest !!!
I think your video answered one of my questions regarding using EF on the priority valve. My Case 570M XT appears to supply the loader control valve and then uses a power beyond kind of set up that runs to a 0-8gpm flow control valve for the 3 point hitch control valve. Specs for the hydraulic system is around 28.5gpm at 3000psi with a gear driven pump. Does this mean I will have 20+gpm with a possible 3000psi available to use from the EF port to run an Oliver 1615 backhoe attachment I recently picked up? Its a fairly big backhoe and right now has a 540 PTO pump hooked up to it which I would assume makes it open center. The Case 570 does not have a PTO on it but if I am understanding this correctly its possible to plumb the backhoe to EF as well as add a hydraulic PTO motor and quick connects up front for skid steer attachments using the EF and correct diverter/control valves etc? Any help is appreciated!
I want to run a brake booster off the steering circuit of a forklift. Orbital motor is open center. Would going to a "power beyond" orbital be best, or would you just use a priority valve, favoring steering (booster demand is very minimal 700 psi max and flow is low too)
Hi, I have a doubt. If you block CF, the pressure increases and the spool allows the oil to pass to EF, right? My question is how much is the maximum pressure in CF and what determines it?
maximum pressure at CF is effectively limited by the LS relief. The relief limits Load Sense therefore limiting maximum. Maximum will be limited to LS plus spring value. Some systems may also include a second relief valve for protection. There may also be port reliefs built into some Hand Metering Units (Steering Control Valve)
@@hydraulics Thanks for your reply! I have another question, in the video, you mention that the spring preload is about 200 psi over that the spool starts to move, which is the pressure that moves the spool fully to EF? is the spring maximum force, but I don't know if it is low or hight. If you connect EF to the tank, just a little pressure over 200 psi moves the spool, so the pressure at CF in a way is determined by EF. What am I missing here?
@@matiasquaglia5021 sounds like you have it. But that spring chamber becomes pressurized when you steer and the load sense pressure comes in and floods the spring chamber. Then the spool must overcome pressure plus the spring.
@@hydraulics thank you very much! I already understand how it works. I'm working on a numerical model of a priority valve, I can't find a numerical value of the spring constant. I need it to know the pressure that moves the spool fully to the EF. Do you know any approximate value of the spring stiffness?
@@aidwilli pretty much. The sequence valves I have encountered will send oil to the secondary circuit at a fixed, set pressure. Whereas the priority valve adjusts itself based on load. Good question!
Hi Sir, I dont understand something in your explanation. Let say we are at standby and oil coming from the pump and going to the Orbitrol is dead ended at the closed center position, it goes through the small hole and then to the back of the spool and then flows through the spool to the spring chamber back to the LS port , which will end up in the orbitrol case. With no steering that spool is never going to shift, because all the pressure coming from the pump is then dumped in the orbitrol case. There will be no back pressure to shift the spool. Please clarify.
I think I got it. Inside that spool there should be a pilot hole. So that at standby the pressure on the spring side is orbitrol case drain plus spring pressure and as soon as the pressure at the other side of the spool is going to match case drain pressure plus spring pressure there should be spool shift. Thanks in advance Sir from Canada.
@@cecilendamb7935 there are two orifices in the spool. The orifice to the pp plug side is a bit larger than the orifice that feeds oil to the ls side. I forget the orifice sizes but definitely creates a pressure imbalance at the spool to help it shift. I'm in Ontario
just wondering, by dumping excess flow, does the valve creates heat? i mean if the standby is too long, its going to heat up right? asking because i have not use the priority valve before
I have never worked on a JCB, but I found a free schematic on scribd. looks like priority valve is at or built in to the steering control valve. Also looks like that machine has 2 pumps. One dedicated implement pump and then the steering priority valve adds the second (steering) pump's flow when not steering via the priority valve to the implement system. cool. Also looks like they make Load Sensing Steering right in that valve - we have a Link Belt D16 truck with that same steering valve with the priority valve built in to it. Truck is made in UK, so probably the same deal.
![[Hydraulic Steering] Orbital Valve Rebuild and How it Works](http://i.ytimg.com/vi/kflK40LN2XI/mqdefault.jpg)
Already an old video but couldn't be explained better , thanks a lot
Very useful explanation. Many thanks
I agree with Warren, you should have many more views on this channel,great explanation thank you. I’ve subscribed 👍
I have a cat backhoe I recently acquired. My first piece of equipment tbh. After a few days of use, I lost the right steering. I couldnt find anything that explained anything as thorough as your video. I wish I saw it before I paid an arm to have dealer service come out for a diagnosis and a leg for them to get me to replace the orbitrol on my own which didn't fix anything. ( the new one actually goes right slower than the older one and will kick back a bit). Your video gave me a couple new avenues to look into and it should save me the last 3 limbs i have 😅.
Excellent explanation using the components too. Thanks
Thanks buddy for this insightful tutorial ,its actually a good pointer for one project i am working on .i haev got a CAT forklift DP40KL , which has a stiff steering problem which started after the hoist contol valve was changed and i presume there is indeed something wrong with the circuitry and most probably the hydraulic pump could be a FDP and no priority valve in the circuit .
EXCELLENT video but I hoping for a troubleshooting section for priority valves because Ive been having an issue I cant figure out on my Allmand TLB. Maybe you can steer(/pun) me in the right direction. Im here because I think Ive narrowed it down to the priority valve but want some reassurance before I break into it.
The machine starts fine and runs fine. The minute I touch the orbitrol steering wheel the engine bogs down hard and all other TLB functions slow to a crawl and it stays that way until I actuate the loader valve in anyway. Then the engine picks up and full function is restored until I touch the steering wheel in anyway again and I have to repeat the process. The hydraulic fluid also seems to get really hot after some use.
So far Ive had the steering hydraulic cylinder rebuilt. It was leaking and it started a slow leak again right after rebuild.
I checked all the orbitrol lines for blockage.
I tore apart the orbitrol to look for problems. Looked clean.
The only thing I think I have left to check is the load-sensing priority valve on the pump itself. Its an Eaton Series 26 Single Gear. Its referred to in the Eaton manuals as a load-sensing priority valve and the description of it mentions that "the excess flow(EF) is available for auxiliary circuits".
Could the issue be related to the priority valve or the loader valve or either/both? Which should I attack first?
I really liked your explanation. Keep up the good work!
best teaching so far
Thank you for making this videos with your effort i subscribed to your Hystat channel and like all your videos
Great video and waiting the complete steering circuit
Hi it's quite more understanding , thank you sir , I have question or doubt , what is the consequences if the priority valve load sense relief is blocked by debris or the port is blocked manually ??
Dziękuję Ci bardzo za ten film i życzę wszystkiego dobrego
You should have way more views than you do.
Feel free to link or mention whatever and all the best in 2020
@@hydraulics I will, thank you.
@@hydraulics pretty impressive that someone with the skills that Warren has in complex equipment repairs sees high value in your videos!
@@byronmill yeah. And I'm about ready to pull all my videos. RUclips for whatever reason really buries my content. Almost no views
@@hydraulics I'm really glad you didn't! One of your videos from several years ago helped me out.
Now for the rest of the catalog :-)
Thank you for very goooooood information 🙏 u the best 👌 👍
great...thank you for such brief explanation
Can u explain how excavator pump regulation system works?
High quality video. Thank you
Good explanation! Thanks a lot sir!
In the Alberta Apprenticeship books, they show an HMU from a CAT scraper with just 3 hoses hooked up and the bottom left port plugged. All the 3 hoses could be a 3/4 ID and run from the HMU under the cab floor through the frame. The top left port has a sort of nipple. I have no idea why it's set up like that. The bad thing is that I'm studying on my own and don't know anybody with that king of expertise... Anyway great video
Interesting they would choose a scraper. Cat scrapers i worked on had a very unique steering system with a follow up cylinder that sort continually re-entered the system. I'd have to dig into it.. been years. Are there that many Cat scrapers in Alberta? Scrapers are nearly extinct in eastern Canada. Replaced by 6wd trucks and mass excavators. Something that specific to one family of machine from one manufacturer should not be in apprentice curriculum imo
The bigger units like a 657 very likely use flow amplifier steering where the HMU is only controlling pilot oil to a remote valve that handles large volume flow to the steering cylinders
@@hydraulics There are hundreds of scrapers (20 years old or brand new) especially in Calgary and Edmonton to build roads outside the city and level new subdivisions, many gravel pits use them to strip the overburden. Recently there are buggy scrapers hooked up to rock trucks like CAT 740 or Volvo AD 40: they remove the box and connect the scraper hitch onto a fifth wheel on top of the rear truck frame. The company making this buggies is called KTec. I'm studying for my Red Seal and there is a pile of stuff to review... Thanks for your interest !!!
Good video ! thank you !
Excellent tutorial! Cheers
I think your video answered one of my questions regarding using EF on the priority valve. My Case 570M XT appears to supply the loader control valve and then uses a power beyond kind of set up that runs to a 0-8gpm flow control valve for the 3 point hitch control valve. Specs for the hydraulic system is around 28.5gpm at 3000psi with a gear driven pump. Does this mean I will have 20+gpm with a possible 3000psi available to use from the EF port to run an Oliver 1615 backhoe attachment I recently picked up? Its a fairly big backhoe and right now has a 540 PTO pump hooked up to it which I would assume makes it open center. The Case 570 does not have a PTO on it but if I am understanding this correctly its possible to plumb the backhoe to EF as well as add a hydraulic PTO motor and quick connects up front for skid steer attachments using the EF and correct diverter/control valves etc? Any help is appreciated!
I want to run a brake booster off the steering circuit of a forklift. Orbital motor is open center. Would going to a "power beyond" orbital be best, or would you just use a priority valve, favoring steering (booster demand is very minimal 700 psi max and flow is low too)
Very well explained ! Mucho gracias!!
Hi, I have a doubt. If you block CF, the pressure increases and the spool allows the oil to pass to EF, right? My question is how much is the maximum pressure in CF and what determines it?
maximum pressure at CF is effectively limited by the LS relief. The relief limits Load Sense therefore limiting maximum. Maximum will be limited to LS plus spring value. Some systems may also include a second relief valve for protection. There may also be port reliefs built into some Hand Metering Units (Steering Control Valve)
@@hydraulics Thanks for your reply! I have another question, in the video, you mention that the spring preload is about 200 psi over that the spool starts to move, which is the pressure that moves the spool fully to EF? is the spring maximum force, but I don't know if it is low or hight. If you connect EF to the tank, just a little pressure over 200 psi moves the spool, so the pressure at CF in a way is determined by EF. What am I missing here?
@@matiasquaglia5021 sounds like you have it. But that spring chamber becomes pressurized when you steer and the load sense pressure comes in and floods the spring chamber. Then the spool must overcome pressure plus the spring.
@@hydraulics thank you very much! I already understand how it works. I'm working on a numerical model of a priority valve, I can't find a numerical value of the spring constant. I need it to know the pressure that moves the spool fully to the EF. Do you know any approximate value of the spring stiffness?
@@matiasquaglia5021 in our Volvo G976 grader for example, the spring specification is 245 psi
Awesome video 👏
Hi, I love your content - thank you for producing these videos. My question is this: how does this priority flow valve differ from a sequence valve?
To answer my own question, the difference appears to be the load sense line to the pressure compensation spring.
@@aidwilli pretty much. The sequence valves I have encountered will send oil to the secondary circuit at a fixed, set pressure. Whereas the priority valve adjusts itself based on load. Good question!
@@hydraulics thanks again
thankyou sir☺️ very detailed information
would be clearer if you show the complete circuit. but its good enough. thank you
Great video
keep it coming sir
thanks you very much
Hi Sir, I dont understand something in your explanation. Let say we are at standby and oil coming from the pump and going to the Orbitrol is dead ended at the closed center position, it goes through the small hole and then to the back of the spool and then flows through the spool to the spring chamber back to the LS port , which will end up in the orbitrol case. With no steering that spool is never going to shift, because all the pressure coming from the pump is then dumped in the orbitrol case. There will be no back pressure to shift the spool. Please clarify.
I think I got it. Inside that spool there should be a pilot hole. So that at standby the pressure on the spring side is orbitrol case drain plus spring pressure and as soon as the pressure at the other side of the spool is going to match case drain pressure plus spring pressure there should be spool shift. Thanks in advance Sir from Canada.
@@cecilendamb7935 there are two orifices in the spool. The orifice to the pp plug side is a bit larger than the orifice that feeds oil to the ls side. I forget the orifice sizes but definitely creates a pressure imbalance at the spool to help it shift. I'm in Ontario
@@hydraulics currently I am in Montreal!. Thanks Sir
Nice definition, thanks🌺
pro tip: watch movies on Kaldrostream. Been using them for watching all kinds of movies during the lockdown.
@Enrique Briggs yea, I've been watching on kaldroStream for months myself :D
just wondering, by dumping excess flow, does the valve creates heat? i mean if the standby is too long, its going to heat up right? asking because i have not use the priority valve before
Yes. Holding oil back at standby will create some heat.
Sir make the complete steering hydraulic circuit ...it's urgent sir plzzzzz make
Fucking amazing
i cant find this valve in jcb 3dx backhoe.. plz help
I have never worked on a JCB, but I found a free schematic on scribd. looks like priority valve is at or built in to the steering control valve. Also looks like that machine has 2 pumps. One dedicated implement pump and then the steering priority valve adds the second (steering) pump's flow when not steering via the priority valve to the implement system. cool. Also looks like they make Load Sensing Steering right in that valve - we have a Link Belt D16 truck with that same steering valve with the priority valve built in to it. Truck is made in UK, so probably the same deal.
Plise xplic for jcb 3cx 2014
Like add thnk you.