Flashpoint of Hydraulic oil

int mind blowing anware....

nilesh from MRPL, INDIN.

It can become flamable if the vapor temperature is high enough. The atomization has as effect only a drastic increase of the contact surface between oil and air. But only if the temperature is high enough it will burn. It is necessary to start the chemical reaction and this can be done only if athreshold is reached.

The oil is being heated the effects of being pressurized by the pump. Hydraulic oil can get very hot as its worked. The size of the tank is usually determine by this heat build up. A larger tank has more surface area to dissipate the heat and more oil will hold more heat. If the fluid level drops then there is less surface of the tank to dissipate the heat an less oil to hold it. I have seen where hydraulic oil has gotten so hot that it melted the plastic that the sump filter had been made of. At this temperature you would have flammable gases being expelled from the tank breather as the fluid level changes. In a enclosed environment they could build up enough to be ignited by the spark at the contacts of a motor starter. Even with out the excessive heat a small rupture in a line could spray oil in fine enough particles to cause the same out come.

Hydraulic oil is aways flammable just a takes a little more to get it going. Its in this heated and atomized state that it become explosive.

Thanks alot for this information it is very helpful.

In your explanation there is an error you let yourself be guided by what happens in a compressor where effectively the air is heated by compression. The heat source in hydraulic systems is the pressure drop in restrictions. This the reason systems with a motor directly connected to the pump will have less heat problems. All leaks are as well sources of heat. What you said with respect to the low level in tanks is correct and usually there is a level control which warns if for any reason the level is too low.

In systems where control leads to high losses (servo valves for instance) it is recommended to have the benefit of a controlled cooling with help of a heat exchanger oil-water or oil-air.

FLASH point and FIRE point.

Both are part of the lubricant or hydraulic oil product's specifications, and are given by the manufacturer's tech sheet.

1. FLASH POINT: is the lowest temperature to which a lubricant must be heated in order to vaporize. At this temperature and with the addition of air it will ignite but will not sustain fire.
2. FIRE POINT: Is the lowest temperature in which the lubricant will vaporize, and with the addition of air will ignite and will sustain fire.

The difference between the two points, is usually 8-10%. A way to determine the quality of the lubricant, is to heat it up to the flash point. If it ignites below it's specified flash point, it means that this is either a low quality oil or lubricant, or it has passed it's useful life. Another good reason to thoroughly bleed all hydraulic systems, and if open to the atmosphere, make sure these temperatures are not reached.

Hope it helps.

Wangito.

The flash point of the fluid we use (and many others) is 227 Deg C (440 deg F) depending on the grade, yours may be different. My memory Que is the title of the Fahrenheit 451, By Ray Bradbury. The flash point for paper.

The test we use is the open cup method. That is: the sample is heated in an open cup in the presence of a hot wire or flame. When it reaches the flash point it goes poof, or something like that.

Hope it helps.

Thanks very much I could not have asked for a better answer. All of the machine rooms for hydraulic elevators are supposed to be ventilated. When I do inspections on new equipment I find alot of Mechanical Engineers and Architects miss this requirement and sometimes it can cost alot of money to fix.Thanks again

The flash point is where the fluid vapor or il is at a combustable level should an ignition source be present. The fire point is the temperature at which the fluid will self ignite.

First of all you should never be runnning a hydraulic system over 155 deg for industrial applications and 180 deg F for mobil application...which is well below the flash point of any oil. If your operating temperatures are above this you have a poorly designed system or there are components that are not properly adjusted...such as relief valves, reducing valves, flow controls, etc. The pump compensator could be set lower than the relief valve, which would create a big heat source.

If you still have problems with high oil temperatures, you should consider a larger air to oil cooler. Even if it doesn't have a fan, simply adding a source for heat dissipation will help reduce heat and the heat loss can be easily calculated.