Hello everyone, We are expecting problems with the hydraulic Vane pump of a CAT wheel loader. We have changed it for two times about every 1000 working hours (from the last change) because it has structural damage mainly in the rotor and port place seizures. Pump number is 146-5076 and serial number of the truck is 3BS00338 of Caterpillar 962G. Can anyone please help in determining what can be the problem that damages this pump. Pump has been changed from Caterpillar official dealer with original parts? Thanks in advance
Have you had any oil samples done? Also any pictures of the previous damage as well as condition of filters, suction lines etc. What are the symptoms when it starts to fail and also what is the machine used for as far as operating conditions?
Guess I would add to this list what oil are you using and any chance of a picture of the failed parts?
I would agree with ksh that details of the oil you are using and some photo of the inside of the failed pump (even the 1st failure if you have them) would be very useful. Before expressing an opinion, a few questions: - 1. Do you have oil samples taken from the hydraulic system on a regular basis and analyzed for particle count..? 2. You state that the first pump failure was replaced using a genuine Cat pump 146-5076. Who actually carried out the work, the local Cat dealer or someone else..? 3. Was the first failed pump disassembled to establish how (and maybe also why) it failed and more importantly to see if there was any chance of metal particles from the failed pump entering the hydraulic system..? 4. Was any type of cleaning done to the hydraulic system after the first failure apart from changing the oil and installing new filters..?
Ensure the hyd tank is sealed and can hold pressure. Ensure the filler cap and breather (it will hold pressure but never a vacuum) are properly sealing and the tank has some pressure when warmed up. All check all suction lines and clamps. We once had a 950 that failed 2 pilot vane pumps before the hyd cap was found to not be sealing properly when installed. They have a hard time pulling hot thin oil from the tank so the head pressure is needed.
Good advice from all of the above. Without any facts to go on, my first two guesses are: A) Restricted suction line B) Sucking air to the intake somewhere Bonus answer: Pressures set too high. Vanes typically are pretty tough.
Bearing in mind it was a vane-type pump (whose wear rates are extremely sensitive to contamination in the system) and depending on maintenance practices and how many hours the machine had worked up to the point of the first pump failure I'd speculate that the 1st failure was probably a combination of old age and less-than-optimum maintenance practices, and the 2nd failure was most likely a result of not cleaning out the system thoroughly after the 1st failure. My 2c - YMMV ..........
Agree with Nige,,, the first pump wore out and who ever replaced the second pump was guilty of not decontaminating the system. If you would put on another new pump without a thorough cleaning one could expect the exact same results. Only at 800hrs or LESS this time.
Also, if the chrome plating is coming off on any of the cylinder rods that would create constant contamination.
Thank you all of you for the replies. I will reply to all of you one by one. Also I will upload some photos for the damaged parts for the first and and the second pump parts! @Bill G The filters and oil have been all changed with original ones. Small parts have been found inside in the first pump damage. Truck suddenly had no hydraulic power, no other symptoms. The wheel loader works in the Port of Durres and is mainly used for moving coal and ramdonly chrome. @kshansen The oil used is BP Vanellus A Multivehicle 15W-40. Photos I wil upload soonly of the both pumps. @Nige Yes I will post the photos of both of them. Time to find the old parts in warehouse and upload parts of first and second pump! We haven t make and contenet particle count of the hydraulic oil. All the work outs and original parts have been carried out from the official dealer CAT! Maintenance have been carried out as the manufactured has programmed. Hydraulic system from the first pump change has been cleaned every part. @Big ben Hydraulic tank is sealed, filler cap and breather looks ok. @lantraxco Suction lines like all the hydraulic system have been cleaned, we will check again for the intake presence of air or dimensions of the hoses. @grandpa System was cleaned. All parts one by one, also changed filters and oil. @partsandservice Yes also, it could be. I will upload some photos.
PHOTOS of first damaged pump
PHOTOS of second damaged pump :
I'd pretty well stand by the comments I made in post #7 regarding maintenance prior to the first failure and also the fact that there was no cleaning of the system carried out after the first failure, especially in view of what the first failed pump looked like ........ Vane-type pumps in my experience react very badly to hydraulic systems that are sucking in dust, usually via leaking cylinders. The leaking cylinders suck dust in via the head seals, also dust can be introduced into the hydraulic tank as a result of the need for frequent top-ups of oil that are a direct result of the leaking cylinder(s).
What pressure is the main relief set at. The 980g quit using a vane pump because of high failure rates. They were running the pumps at 3000 psi but the large size of that pump made it only safely rated to 2500 psi.
Here's what it says in test and adjust section for main relief: "Increase the engine speed to high idle. Observe the pressure gauge and move the lift control lever to the RAISE position. On a standard machine, the pressure setting of main relief valve (5) should be approximately 20700 ± 340 kPa (3000 ± 50 psi). On a logging machine, the pressure setting of main relief valve (5) should be approximately 20700 ± 340 kPa (3000 ± 50 psi)."
I was going to say, I've never seen the rotor fracture like that unless it was a case of overpressure or shock loading, YMMV.
Yes, I have seen rotor crack like that when a directional valve was placed before the relief
Back "in the day" when just about all the front end loaders we had in the company, Houghs and Cat among others, ran Vickers vane pumps I replaced dozens of those cartridges. Actually I believe there are a couple spare ones out in the back shop right today! Anyhow out of all those 99.9% of them had very worn cam rings and don't recall any failures like that. However as some one mentioned 980 Cat pumps got me to thinking, we did have a pump failure one one of those. Did some checking and see where it failed just short of 10,000 hours at five years old. Even with those hours on it Cat did go "halves" on the up date to gear pump. Below is a picture I have of the center showing the smearing and crack in the rotor. It does look like it was heading for a major failure like the original poster had with his pump. All I can say is our operator stopped running the loader when he felt a vibration in the lines and avoided even more damage. Despite the condition of the pump it was able to make it through a relief valve test before it was opened up.
Would also like to mention, anytime a pump is replaced the suction line should be also. VAne pump don't develop much vacuum and air under pressure will erode th surfaces of the pumps internals and the valves down ******
I have pulled a pump out of a G that looks just like the second pump all full of cracks That hydraulic tank pressure relief was full of dust and not pressurizing the tank
Another thought on hydraulic tank breaker relief valves, especially on machines with a vane-type implement pump (not so much with gear pumps, they are a bit more tolerant). On a lot of our machines we are replacing the tank breaker valve on a 2000hr PM simply because it's easier to spend a few $ on replacing the valve while you know it's still good as opposed to chasing your tail via pump failures, etc, etc, only to find that the root cause of failure was a $50 tank relief valve that nobody ever thought to check "because it looked OK from the outside" .......... yea, right ............