Insane Hydraulics
Bold and audacious blog about fluid power
The last time I had an opportunity to open and inspect a perfectly functioning pump with a proven service history was with a 7500 hour old Rexroth A10VO, and this week, due to another "lucky accident" (lucky for me but, of course, not for the owner) I received a unit twice as old - a Parker P1-100 medium pressure open circuit pump with almost 15,000 confirmed hours of operation.
This pump is the primary pump from an Atlas Copco CS10 drilling rig. The unfortunate reason why it had to be disassembled can be seen here - the shaft seal appeared to be leaking, and when the mechanic tried to remove the seal - it ended up inside the pump.
Here is the picture of the engine info screen from the previous service. I didn't have the opportunity to power the rig to check the current reading, but the machine has clocked at least five hundred hours since then, so it is safe to assume the total amount of running hours for this particular pump should be above 14,500.
The rig is powered by a diesel engine, the hydraulic oil in the system is common mineral anti-wear, 68 grade, working temperature between 60 and 70C, the system operates at 1800-1900 rpm, the pump compensator pressure is set to 280 bar and the delta P to 20, the drilling motor DCV spool draws about 160 liters per minute.
The rig has always belonged to the same company and had all the maintenance done by the same crew. Also - the mechanics who serviced it were very proficient with hydraulic systems - so the system's adjustments and correct operation have been verified regularly. No extras - like additional offline filtration, or improved air breathers - just "proper" regular and careful maintenance with quality consumables and experienced techs.
And now - we have a rare opportunity to see the result of it. 14,500 is a respectable amount of hours for any pump, especially in a mobile application.
Let us begin with the shaft. The front bearing and its race and the tail bearing and its race present normal wear marks. They look almost new to the naked eye. For this pump model, the B-10 bearing life is between 10,000 and 12,000 hours for 1800 rpm and an average pressure of 250 bar. The shaft seal surface has no wear whatsoever - just minor marks. This means the shaft seal area was clean, the oil was clean and the case pressure was normal. The splines that work inside the barrel look brand new, they are marked just enough to confirm the direction of rotation. The same goes for the main shaft splines, which tells me that the coupling was nice and tight.
Now let us move on to the swash-plate mechanism. The swash-plate surface looks untouched. Seriously. The cradle bearing liners do have some wear marks, which is normal, and of course, the liner from the pressure side did develop a groove, however in my opinion this is nothing for 15,000 hours. I have received several P3s this year with a couple of months of operation on them with similar amount of wear (I have a very, let us call it... strong, opinion about Parker's P2s and P3s, which I will publish another time). The respective surfaces on the pressure side and the suction side are well polished and free of scratches, which once again tells me that the filtration on this particular rig was kept pristine. The cam on the servo-cylinder side did suffer from wear, and, of course, there is a respective groove on the piston. This is to be expected, as well as some wear on the side of the piston and the liner. Now the bias side is spotless. Look at the bias piston - zero wear on its side, very little wear on the top (same goes for the respective liner). It seems that the black surface finish (Parkerizing?) does work!
Moving on to the rotary group components. First - the valve plate, which will tell us all about the oil quality. No deep scratches, no small scratches here. Some discoloration, and minor signs of cavitation. Again - for a 15,000-hour unit this is flawless. The suction line and the pump inlet are well designed, for sure.
The barrel tells us the same story. No scratches or groves - nothing but normal wear.
Now for the part that always wears out - the ball guide pins. Surprisingly, the wear is very small. The pins did leave marks on the ball guide, but I've seen worse. much worse! The ball guide looks clean, as well as the retainer plate. The wear to the spherical surface is minimal.
Let us have a look at the pistons. Clean side. Clean slippers. Almost new. I did feel a small play in the shoe - something I can't show in a picture, but again - the play was minimal, and the piston reusable. I am sure that it will run problem-free for another 5000 to 10,000 hours.
So - here you have it. A medium pressure unit that has clocked 15,000 hours in a mobile application with very little wear. Proper maintenance at its best!
I also think that the pump design helped here. I am not sure at all that, for example, a Rexroth A10VO100 with bronze piston slippers and swash-plate liners would show an equal amount of wear in this application.