room temperature 3

[JTBuer]

We have a hydraulic system to raise and lower 6' gates in a dam. The manual for the dam states that the control building temperature should not be allowed to drop below 50 degrees farenheit to keep the hydraulic systems warm. The dam was built in 1967. Now I'm wondering why the temperature has to be maintained since many machines work outside in much colder temperatures.

 

[hydromech]

The main reason would be oil viscosity.

Performance of the system would degrade as the oil became thicker. The primary risk would be to the pump as it would not be able to fill as easily as it would with warmer, less viscous oil. Pumps that cannot suck enough oil in tend to die very quickly.

Other machines that work outside are designed with low temperatures in mind. Bigger pump inlets, flooded pump suction lines, reservoir heaters.

it is often the case that such notices are placed in the manual retrospectively. That is someone forgot to install a heater and rather than spend some money they just draw up a quick warranty "get out".

'hope this helps..

Adrian

 

[hydtools]

Adrian covered it. The system may become sluggish. You should be able to warm the system before you have to operate the gates if your system is very much below 50F. Running the system without operating the gates will warm the system. The circulating losses will warm the system.

Mobile systems do startup at lower temperatures. General practice is to run the system without doing work until the system warms.

What fluid are you using? The temperature caution statement may no longer apply for the fluid you currently use.

Ted

 

[IceStationZebra]

There is also the potential for water in oil issues. The higher temp would help prevent this. I'm sure the additives available 40 years ago weren't as good.

I also agree with hydtools on the viscosity. You should be able to switch to a multi-viscosity oil to help run in cold conditions.

ISZ

 

[JTBuer]

Thanks
I was hoping a better oil would allow us to lower the temperature but wasn't sure if there might be some other problem that wouldn't occur to this civil engineer. It costs us about $1600 a month to heat the control building so pehaps we can save a few dollars.

 

[hydtools]

When you select an oil consider the maximum viscosity at cold startup. Generaly, pump manufacturers recommend no higher than about 4000 to 5000 SSU, 800 to 1000 cST. Knowing your minimum startup temp, you can select a hydraulic fluid which will work for your temperature range from cold to working system temperature.

Here is a piece of literature from Chevron.

https://www.cbest.chevron.com/generated/MSDS/PDS7669415.PDF

Other suppliers can provide information too.

Ted

 

[hydtools]

Here is a sample viscosity chart showing three ISO grade of oil. ISO32 what we use in mobile systems for most outdoor uses. It has a high VI(viscosity index)and good low temperature startup viscosity.

http://www.hydrosafe.com/products/viscosity.htm

Ted

 

[IceStationZebra]

I was curious about some details.
- Does the pump run all the time or just as needed, and if so how often is this?
- Does the oil run out to each lock? If so is it in the elements or protected?
- What kind of pump do you have? (gear, piston, etc.) If piston is it fixed displacement or variable?
- What pressure does the pump see at stand-by?

Piston pumps do not like to have inlet vacuum. It pulls the slippers off of the swash plate and can cause havoc. A variable displacement pump could be a little better if there is no flow demand at start-up. Gear pumps can generally tolerate some vacuum for ~30 seconds during the occasional cold start. My experience with engine driven pumps shows that the oil acts live a viscous plug - during cranking it doesn't want to move a causes high vacuum, but once it starts moving (10-30 seconds) the vacuum drops quite a bit and becomes acceptable. An electric motor application would be similar but you don't get the luxury of the slow cranking period.

ISZ

 

[kcj]

I take it the problem is cold temp at pump start.
More modern fluids and a tank heater might be a fairly easy fix there.

Slightly OT, but if the issue is cold oil in the lines, and line volume is more than the cylinder volume, the oil never comes back to the tank. It just shuttles back and forth in the lines and stays cold. I've seem aplications that use 4 lines, 2 for A and 2 for B, with checks at each end. Oil goes out in one line and back in the other so it cycles through and warms up. Also used in extremely dirty applications where dirt builds up in cylinders from rod seal ingression if it doesn't cycle and flush.

kcj

 

[JTBuer]

The entire system is in a vertical concrete shaft about 60' high and sheltered from the elements. There are 3 gates and each one has a seperate pump. I think it is a piston type pump but we're not really sure. We'll find out. The system is off most of the time. We just turn it on when a gate change is required. In the spring that can be daily but the rest of the year it is just once every month or two.

 

[budt]

Change he oil to 10W30 Engine Oil and forget the temperature problems.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[JTBuer]

I appreciate your information. Just to correct my earlier commen. The pumps are Denison vane type pumps. They run at 800 psi.

 

[budt]

A setup I have used on long lines that are already installed is a Manual or Solenoid Operated Normally Closed Valve Teed in across the actators ports that can be opened and allow oil to circulate through the long lines until flushing the lines of stagnant fluid.

The Actuators still have old oil but can be cycled once or more and then reflush that oil back to tank.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING