Cold hydraulics

[WVBill]

Mike:
Is the hydraulic reservoir for your loader in the right-hand FEL upright member like mine? I was thinking of just wrapping that upright with heat tape (like they make for keeping pipes from freezing) and leaving it plugged in all the time. There's probably almost as much fluid out in the lines and cylinders as there is in that "reservoir" but I'm thinking that having that fluid "pre-warmed" would be a big help.

I don't know how hot those heat tapes get. Any idea?

Paul got the description right as to why I think the pump is cavitating.

 

[SteveNY]

Thanks all for the info. My tbl had transmittion fluid in the reservoir when I boutht it. For great fear of the 0-rings and seals not being compatiable and having to replace them, I changed to the recommended Hytran (thats right $30/5gal.) oil. When first started at cold temps. the pump makes louder than normal noises when operating the levers and the arms make jerking movements. I think the jello explanination sounds like what is happening. There are magnet type oil pan heaters but I'm afraid that they might be too hot and hurt the oil. I just built a garage with 11 foot high overhead door but it is with out heat. Maybe I can talk my wife into letting me bring my tractor in the house?????

 

[Soundguy]

Re: Cold hydraulics & pump cavitation

In hydraulic systems, cavitation can occur when there is an obstruction in the suction line. The suction on the low pressure side lowers the vapor pressure and any moisture and disolved gasses in the oil can boil out. I soppose depending on the fluid, you might even reach the vapor point of the pumped fluid as well. In any case.. cavitation is bad for the system.. it will start to erode all contact surfaces... that is a real basic explanation
In more specific terms for the other engineering types out there, fluid is not really sucked into the pump, it is pushed in under pressure.. generally atmospheric pressure.. this fluid pressure floods the pump. A pump will have a NPSHR number as determined by the manufacturer ( net positive suction head required )( minim fluid energy needed at the pump inlet for correct opperation ). The NPSHA ( net positive suction head available ) is the force pushing the fluid into the pump. NPSHA must exceede NPSHR or cavitation will occur. Again, cavitation is vaporization of the liquid in the suction line. If the fluid pressure is less than the vapor pressure of the fluid in question, pockets of vapor will form. Once these pockets reach the impellor or piston surface, they will again be acted on by the high local pressure of the pump, and will collaps.. this will cause vibration.
Per the Civil eng/ ref. manual, the following situations can cause cavitation:
"discharge heads far below the pump's calibrated head at peak efficiency.
suction lift higher or suction head lower than the manufacturer's specifications.
Operating the pump at speeds higher than the manufacturers recomendations.
pumping liquids at higher temperaturers than manufactureres spec's ( higher temps will have different vapor pressures..etc )

Soundguy

<font color=green>And how does a full system cavitate if maintained with the proper fluids and filters? I am not questioning that it's cavatating or not but I would like to know how and why now.


I could be wrong, but here is why I think it happans. When the oil in the system is cold it gets a lot thicker. The pump trys to suck the oil from the tank, but the oil is so thick, it does not flow to the pump. Think of