How to choose hydraulic oil for high temperature open flame occasions?

March 29, 2024

How to choose hydraulic oil for high temperature open flame occasions?

What hydraulic oil does high temperature open flame hydraulic equipment use? Fire resistant hydraulic fluids/fluids should be used in high temperature and flammable situations.

There are mainly the following types of fire resistant hydraulic oil/fluid:
HFAE: oil-in-water emulsion type flame retardant hydraulic fluid (water content greater than 80%)
HFAS: Water-based flame retardant hydraulic fluid (water content greater than 80%)
HFB: oil-in-water emulsion type flame retardant hydraulic fluid (less than 80% water content)
HFC: non-flammable hydraulic fluid containing polymer aqueous solution (less than 80% water content)
HFDR: Ester type flame retardant hydraulic fluid

1.HFAE oil-in-water emulsion due to the water content of more than 80%, therefore, it has high specific heat, good fire resistance, excellent cooling performance, and cheap, harmless to the human body, and good adaptability to general non-metallic materials. However, because it is a water-bearing liquid, the steam pressure is high, and the lubrication is poor, the use temperature cannot exceed 50 ° C, and the system pressure cannot exceed 7.0MPa. It is suitable for coal mine hydraulic support hydrostatic hydraulic system and other hydraulic systems or mechanical parts that do not require recycling waste liquid and do not require good lubricity, but require good flame retardant liquid.

2.HFAS water-based flame retardant hydraulic fluid, also known as high water-based fluid, is usually composed of 95% water and 5% water-soluble chemicals. It is non-combustible, non-compressible, has high heat capacity and thermal conductivity, and has good cooling effect. The operating temperature of the system is usually lower than that of oil systems. Low viscosity, dirt precipitation fast, cheap (only 1/5-1/10 of the cost of mineral oil), non-toxic, pollution-free, easy to handle. The use temperature is best in 4 ~ 50℃, the temperature is too low may freeze, too high, evaporation too fast. The lubrication of water is poor, so the system pressure it runs cannot be higher than 7.0MPa. In addition, it is not suitable for aluminum, magnesium, lead, zinc, galvanized steel (material), cadmium metal materials, and cork, paper, butyl rubber, leather, most coatings and coatings are also not suitable. Pay attention when using. Suitable for low-pressure hydraulic systems and machinery such as metal processing that require non-flammable liquids.

3.HFB oil-in-water emulsion is composed of 60% mineral oil and 40% water, and fine water particles are dispersed in the continuous phase of mineral oil, and water is a fire-resistant component. Water-in-oil emulsions have relatively low lubrication properties compared to mineral oils, which limits their use in high-pressure systems. Due to the water content, the steam pressure is high, and the maximum temperature used can not exceed 65 ° C. One of the main problems in the use of water-in-oil emulsion is its stability. Long-term standing, high temperature and pollution will cause phase separation, and the emergence of phase separation accelerates premature damage to the pump. The main advantage of water-in-oil is that it can use the same non-metallic materials as mineral oil, including seals, hoses and coatings. In addition to magnesium, can be adapted to general metal materials. Suitable for medium and high pressure, high temperature and flammable systems in metallurgy, coal mining and other industries.

4.HFC water-glycol liquid is also a kind of anti-fire hydraulic fluid with water as an anti-fire component, which is composed of 30-55% water and 25-45% glycol, glycerol or its polymer and water-soluble thickener, anti-wear agent, anti-rust agent, anti-foam agent, etc. The liquid has excellent fire resistance, high viscosity index, good stability and fluidity, and is a transparent true solution. However, the use temperature can not exceed 65 ° C, generally used in a pressure system not higher than 10MPa, it can use the same sealing materials and hoses as mineral oil, but it is incompatible with zinc, cadmium, magnesium, silver and untreated aluminum, and can not use leather and cork. It can soften ordinary paint and can only be used on epoxy based paint or vinyl paint. Ethylene glycol has certain toxicity and should be prevented from entering the mouth, but it does not harm the body. Suitable for low and medium pressure hydraulic systems in metallurgical and coal mining industries.

5.HFDR ester type synthetic fire resistant hydraulic fluid. This kind of fire resistant hydraulic fluid has high spontaneous ignition point, low volatility, good fire resistance, and lubrication performance is comparable to the best mineral oil. Can adapt to most metal materials. However, because of its large polarity and strong solubility, usually mineral oil can adapt to the general non-metallic materials such as nitrile rubber, neoprene rubber, asbestos rubber sheet, polyvinyl chloride plastics, plexiform glass and vinyl paints, it is not suitable, and must be carefully selected to match the material. There are mainly two kinds of ester type flame retardant hydraulic oil, one is phosphate ester type, the other is fatty acid ester type, of which phosphate ester type has a long history, the use of temperature range of -50 ~ 135℃, suitable for metallurgy, thermal power generation, gas turbine oil and other high temperature and high pressure operation hydraulic system. However, due to its poor hydrolytic stability, highly toxic hydrolytic products and greater harm to the environment, it has been gradually replaced by fatty acid ester type flame retardant hydraulic oil.

How to choose hydraulic oil varieties according to special needs
In addition to considering the working pressure, temperature, and use environment, there are some more detailed factors in the choice of hydraulic oil varieties:

1. According to pump type
For example, according to the working pressure and temperature: pressure <7.0Mpa, temperature <50℃, use HL; The pressure is 7.0 ~ 14.0Mpa, and the temperature is 50 ~ 70℃ HL or HM; Pressure >14.0Mpa, temperature >70℃ use HM.
Depending on pump type: vane pump is recommended to use HM high zinc content (Zn > 0.05% in oil); The plunger pump uses ash-free anti-wear hydraulic oil, and the general pressure can be HL hydraulic oil; Both the plunger pump and the vane pump use HM low zinc (Zn < 0.03% in oil); Gear or screw pumps use HL or HM.

2. According to special parts
The hydraulic system contains silver-plated parts with special anti-silver hydraulic oil; CNC machine tool oil although in indoor work to choose HR high viscosity index hydraulic oil; Some hydraulic systems have high precision servo valves to choose clean hydraulic oil; The feed system of the machine tool requires the oil to have good stickiness, so HG hydraulic guide oil is selected.

3. Hydraulic transmission system
PTF-1, also known as automatic transmission fluid (ATF), is used for automatic transmission systems of cars and light trucks; PTF-2 is used for heavy duty truck, off-road vehicle transmission system; PTF-3 is also known as hydraulic, transmission dual-purpose or hydraulic, transmission and brake three oil for agricultural and construction field machinery hydraulic transmission system.

4. Environmental factors
Biodegradable lubricants include: HETG belongs to vegetable oil type; HEPG is polyether based oil; HEES is a synthetic ester based oil. HEPR is a polyalpha-olefin synthetic oil.

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