Hydraulic Oil 2

[KyEngrSara]

Hey everyone!
I need help on hydraulic oil! I am very green - just out of school, and having a hard time finding out the right information on hydraulic fluid.

I have 3 fluids I am choosing from. I need to know the temperature range that these were designed for...

The thing is, everywhere I go, it seems to reiterate that what I REALLY need to know is the optimum viscosity my hydraulic system was designed for.. and from that I can look at my desired system operating temps and pick the grade from a chart.

Is this all correct? Any help would be greatly appreciated!!! Thanks!!!

 

[MintJulep]

The manufacturers' of hydraulic fluids want you to use the right stuff for your application, and all have web sites where extensive technical data is available. If you don't see what you need on the web, there is generally a phone number to call where you can speak with a person knowledgable about the product.

This holds true for many similar products.

You need to learn how to ask questions. Your post asked only one question. The answer to that is "no".

 

[BillPSU]

There are cases where the normal operating temperatures are not maintained within a system such as in an aerial device which uses pilot operated valves. The problem for these cases is the ambient temperature you are working in. The pilot valve flow very little oil at low pressures with long 40'-60' lines. Talk with the oil supplier and have an idea of either your operating temperature or ambient temperature and what controls your viscosity. It will probably take real world experience to pick the best oil.

 

[KyEngrSara]

I have talked with 1800-lube-tek and with amsoil technical support. and visited many websites. they all state that they can't give me a range for their oil. It seems they are baffled that i even ask that question.

My supervisor tells me that all over the web there are operating ranges, and that that is how oil companies design their oil.

I can't get this information from the suppliers. I don't know who else to talk to, and my reference books aren't helpful either. they all say that i need to know the viscosity, and from that i see if the oils i have fall within that range.

so i have one question:
1) is synthetic oil designed/tested based on temperature range to see what temperature it can withstand before oxidation occurs?? because that is the "range" i need.

as i mentioned above, i have read technical data sheets, manufacturer's recommendations, msd sheets, and talked with several suppliers. i can't get the answer anywhere.

thanks.

 

[CoryPad]

Amsoil? You should be talking with larger suppliers with real technical capabilities. BP, Chevron, Conoco, Exxon, Houghton, Mobil, Shell and Texaco all supply industrial hydraulic oils.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[maytag]

The heart of your system is the hydraulic pump and any hydraulic motor-if you can get the model numbers of the componets you should be able to access online the needed info. All the pumps I have installed have a viscosity chart showing the ideal range. A well designed system will have the needed heat exchanger and heaters to maintain correct operating temp. There may be other factors that you have to consider when choosing a hydraulic oil-pump RPM,suction setup,biodegradeable fluid,fire retardant fluid,etc. As I am in a steel mill almost all my systems are run on water glycol and componets are sized to maintain 100-120F.

Maytag

 

[KyEngrSara]

I have spoken with "engineers (according to the phone directory) at texaco, shell, mobil, and chevron. again, the issue isn't who i've spoken with, the question is regarding the design of hydraulic fluid.

thanks maytag, i will go check the pump to see if i can get any info from that! appreciate your help!

 

[JJPellin]

The manufacturer of the hydraulic pump should specify what ISO grade of oil they recommend. Your conditions will dictate whether you need a mineral or synthetic. The pour point of the oil needs to be well below the lowest temperature that the oil is every expected to see. If the highest temperature in the system is hotter than about 250 °F, you should probably use a synthetic for oxidation resistance. If the temperature range you expect in your system is too great, you could use a reservoir heater to keep the oil from getting too cold and a cooler to limit it from getting too hot. Most of the time we end up using a synthetic for one reason or the other. We use Automatic Transmission Fluid in a lot of systems and ISO 32 synthetic turbine oil in others. A few systems have pumps that require a heavier oil and so we use an ISO 46 or 68 synthetic.

 

[IceStationZebra]

Generally the viscosity is a trade off between pump inlet vacuum at cold temps and lubriaction and oxidation at high temps.

Most gear pump manufacturers want <10inHg at start up and <5inHg during normal operation. So this takes into acount inlet piping, oil viscosity, inlet screen, lowest expected temp, ect. I think that piston pumps can't handle as much vacuum, but I'm not sure.

On the high end you risk excessive wear if the oil is too thin during "normal" operating temperatures. If the oil gets too hot oxidation gets out of hand, but of course that depends on what you want for a service period. I have never found solid data, but a rule of thumb is that oxidation doubles for every 10deg F. And most hydraulic seals and rubber components are designed for ~220 deg F. Above that you will start to get more cases of leakage, etc. Its a catch 22 where the suppliers keep supplying componts designed for 220F because the machines are designed for 220F max ..... because the components are designed for 220F.

ISO 32, 46, etc are fairly generic oils and can vary quite a bit, especially if you take shear-back into account. Synthetic oils will generally get you better viscosity at higher temps, the negative being cost. I have also used ATF as a cold temp oil. Tractor hydraulic oil is fairly crude.

As was mentioned before...it all comes down to viscosity. You need to find an oil that will satisfy both cold and hot temp conditions based on your system. Good luck.