Cat pumps and some more pumps!!!

[Noob_Technician]

hello world

i am still in school studying and ive been thinking about what types of pumps Caterpillar uses for hydraulic and fuel......now this may be a difficult question to answer because there are a wide range of machines but im mostly curious about, bulldozers, backhoes, excavators, articulated haul trucks loaders and skid steers and hell if someone knows what type of pumps those huge mining trucks use you can also let me know :bouncegri

from my knowledge the fuel pumps are : vane, gear, hand primer, diaphragm, and plunger
for hydraulic i believe it is: radial piston, axial piston, vane, gear, and bent axis piston

if i missed any pumps feel free to correct me and i hope to get some answers about the different pumps

 

[John C.]

I don't recall ever seeing a Cat using a radial piston pump. Axial piston, vane and gear pumps are the usual culprits. Most everything nowadays used some sort of axial piston pump either open center or closed center with some type of load sensing system.

 

[repowerguy]

I agree with you John, radials are pretty much Deere territory, noisy things are tough though!

 

[partsandservice]

Here is a question to research:


Which options make a group ( there may be more than one correct answer)?

A. Vane pump, open center valve, charge pump

B. Bent axis piston motor, vane pump, axial piston pump

C. Charge pump, axial piston pump, bent axis piston motor

D. Gear pump , closed center valve, actuator

E. Gear pump, open center valve, actuator.


2. Define hydrostatic.



Kind of a joke, but seriously if you can answer these you will be much further along than many.

 

[Noob_Technician]

well im not really sure what you mean by "make a group"..................

A- sounds like it can be correct
B- i cant see this one being possible
C- i think this is possible, because i believe this one is used in some skid steers
D- i never really seen a gear pump in a closed hydraulic circuit, but maybe there are
E- :beatsme and sure why not

2- Hydrostatic idk how to explain this but ill try...... most hydrostatic systems are closed looped, and use a charge pump which is close to the hydraulic pump, they also use hydraulic motors for their final drive as a way of movement, so instead of a machine having a transmission, it has those things i just said. I know Hydrostatic is used in skid steers, some bulldozers, and i guess excavators as well

im not too sure how well i did, but i tried and also remember im still in school lol :yup

 

[partsandservice]

You did fairly well. I intended this as food for thought rather than an actuall test. Researching each type in the answers is the point rather than actually answering the question that is why I put it as a research question with you being in school and all. C. Is correct , it describes the components of a hydrostatic system and yes a hydrostatic system is closed loop. E. Is also correct. More knowledge can be gained in personal research combined with schooling.

 

[Noob_Technician]

thanks for the help, things like that will help me out and test my skills

also E, what or where would you see this type of application ?

 

[partsandservice]

E. Is a standard type hydraulic system. Some skid steers have this for boom and bucket . Some log loaders and old excavators , farm tractors, log splitter. So a gear pump makes flow anytime it is turning and has no internal regulation and cannot be deadheaded . An open center valve is always nessesary with a gear pump. When the hydraulics are in neutral the flow just passes through the valve and returns to tank. When the valve is moved the flow is then directed to the actuator( cylinder, motor, accumulator ). When valve is moved off center, pressure relief valve(s) prevent oil deadhead situation.

 

[John C.]

You should probably be a little careful in explaining some things. Gear pumps and closed center valves are used in all the excavators and wheel loaders I've worked on for the last twenty five years. That is how they make a pilot control system work. There are also plenty of combination gear pumps with regulators installed on them.

A hydrostatic system just means that hydraulic fluid is not in constant flow. Excavators, dozers and hydraulic driven wheel loaders are all examples with motors and actuators like cylinders. The opposite of a hydrostatic system is a hydrodynamic system which would include a torque convertor or fluid coupling. That oil is always in motion.

A closed loop system is a variable flow and possibly a variable direction pump and has a path directly to a motor on both sides. Making the motor turn one way means moving the pump swash plate in one direction. Move the swash plate in the other direction from center makes the motor turn the opposite direction. The oil goes from the pump to the motor and back to the pump. There is provision to pass excess oil back to the reservoir or take extra oil from the reservoir as temperatures rise and the components lose efficiency. Old excavator swing systems in Koering excavators and many drills today use the closed loop system. Even many types of hydraulic hammers for this like sheet pile drivers are closed loop systems.

The open loop system has multiple directional control valves to run multiple functions. The oil comes from the reservoir to the pump, to a control valve and back to the reservoir.

 

[Cmark]

OK so not a pump, but the same idea is a radial piston motor. Cat use them in one particular application I can think of. Answers anyone?

 

[Noob_Technician]

i have no idea, i thought cat doesnt use radial design

 

[fergy]

Scrapers?

 

[partsandservice]

John C, I have been through this on this forum before. I am a student and a teacher. I find discussion the best way to learn and teach. If I had not responded to noob I would not have had the opportunity to be schooled. As far as the snide " I better be careful" thing... Would your suggestion be that I no longer post on until I have as much wisdom as someone such as yourself. Help me understand how you regulate the flow of a gear pump with out going over a relief in a closed center. So would a closed center valve and gear pump system require a pressure reducing valve for the pilot and flow dump? Also when would a hydrostatic system not be closed loop and a closed loop not hydrostatic?

To answer Cmark. I think it is the CTL.

 

[partsandservice]

So I did some internet research. A gear pump and closed center valve is possible with an unloading valve but would typically need an accumulator in the system.

 

[John C.]

The comment wasn't snide in any way. I was pointing out that there are plenty of uses for what you were saying isn't done. I was concerned about a newbie perhaps being confused in the future when he runs into systems that are commonly used throughout the industry today. The fascinating thing about hydraulics is just how wide and deep it is today. What was set in stone that couldn't be done twenty years ago are common systems in use today.

As to your question about a open loop or closed loop system it was explained above. The pump outputs are directly connected to the motor and oil flowing through the motor flows directly back to the pump and not to a reservoir. Both open and closed loop systems are hydrostatic.

 

[Cmark]

To answer Cmark. I think it is the CTL.

Good answer. I wasn't actually thinking of CTLs, I've never had a drive motor from one apart but I checked it out and yes, radial piston motor.

What I originally had in mind was the front wheel drive motors on 6x6 graders.