Powered by Blogger.
Monday, 18 November 2013

What is a phosphate ester fire resistant fluid?

Phosphate ester fire resistant fluid has excellent anti-wear and fire resistance properties.

Phosphate ester fire resistant fluid is primarily used as a fire-resistant basestock in applications such as hydraulic systems, turbines and compressors.

Phosphate esters were formerly a common derivative of coal tar and as a result consisted of a mixture of isomeric aryl phosphates, including the neurotoxic orthotolyl phosphate.

However this production method has declined along with the commercial use of coal tar. Today, phosphate esters are commonly derived from the reaction of phosphorus oxychloride
with an alcohol.

Phosphate esters produced in this way are widely used in hydraulic fluids for aircraft, ships, tractors and other vehicles, and as flame-retardant additives for polyurethane foam and similar products.

Modern technology also promotes better control of the manufacture of phosphate ester fire resistant fluid, with a low level of toxicity.

Why use a phosphate ester fire resistant fluid.

Phosphate esters are the most fire resistant of the non-aqueous synthetic basestocks in common use. Their high ignition temperatures, excellent oxidation stability and very low vapor pressures make them difficult to burn, while their low heats of combustion result in self-extinguishing fluids.

Phosphate ester fire resistant fluid displays good thermal stability, excellent boundary lubrication, low volatility and acceptable hydrolytic stability (chemical stability when contaminated by water).

The triaryl version used in the phosphate ester fire resistant fluid is relatively unique among hydraulic fluids because it’s self-extinguishing. The fluid doesn’t create enough energy to support its own combustion in a fire. Other lubricants can burn readily once they reach their ‘fire’ points. In addition, this hydraulic oil has higher flash and fire point, higher autoignition temperature and performs better in spray flammability and wick-type fire propagation tests.

This characteristic makes this the correct hydraulic oil for use in steel and aluminium production, pressure die-casting, glassmaking, polymer forming and many other high fire risk industries.

Disadvantages of using a phosphate ester fire resistant fluid.

The use of phosphate ester-based products in hydraulic applications is still principally dictated by fire-risk considerations. Although inhibited phosphate esters possess excellent oxidation stability and inherently good anti-wear properties under critical loading conditions, they suffer from somewhat inferior hydrolytic stability, low viscosity index and extreme chemical aggressiveness toward many conventional seal and coating materials. These weaknesses limit the use of phosphate ester to specialized applications where a high degree of fire resistance is required.

Other challenges to using phosphate ester fire resistant fluid include:
  • Relatively high cost 
  • Frequent oil changes 
  • Contamination related servo valve failures 
  • Gelling & deposit formation (dissolved metal catalyst) 
  • Expensive system flushing 
  • High acid number 
  • High moisture content 
  • Dark fluid, foul odor (thermal degradation) 
Unfortunately, phosphate esters can also be hard on some elastomers such as Buna-N or nitrile, PVC coatings and paints. However, they are not as hard on butyl, nylon, PTFE, EPR, Viton and epoxy-based paints. Because phosphate ester degradation products can catalyze further degradation, they require vigilant condition monitoring and specialized reconditioning.

Maintenance of a phosphate ester fire resistant fluid.

The user of a phosphate ester fire resistant fluid must accept the need for greater vigilance with respect to fluid maintenance than is normal for conventional mineral fluids.

No longer is it sufficient to periodically change filters, repair the occasional leak and top off the reservoir. On average, phosphate esters also cost five times more than their mineral counterparts.

The majority of fire-resistant fluids display a considerably greater degree of detergency than mineral fluids. Consequently, dirt particles or wear debris do not settle out in the sump as readily. This tendency promotes abrasive wear of pumps and other components along with affecting valve function.

Because phosphate ester fire resistant fluid is a specialised fluid you need to make sure that if your hydraulic system operates under conditions that requires a flame resistant hydraulic fluid, you choose the best. Habot Synthetic Lubricants have products that our professionals can assist you with.