BS ISO 7745:2010 pdf free download – Hydraulic fluid power一 Fire-resistant (FR) fluids – Requirements and guidelines for use.
Emulsions with a particularly small oil droplet size and usually lower mineral oil content are commonly known as micro-emulsions and, depending upon the hardness of the diluting water, may be translucent in appearance.
The finished fluid is usually alkaline, with a pH typically in the region of 9,0 to 9,5.
6.2.1.2 Viscosity
Due to the very high content of water in unthickened fluids, their viscosities are close to that of pure water (approximately 0,8 mm2/s at 40 °C). Accordingly, hydraulic components designed specifically for use with low viscosity fluids are normally used in hydraulic systems filled with unthickened HFAE fluids. Thickened HFAE fluids have viscosities comparable to mineral oil (e.g. ISO VG 32 and ISO VG 46), allowing more conventional hydraulic components to be used; however, the components are still required to operate reliably with the reduced lubricating properties of these fluids.
6.2.1.3 Lubrication properties
The lubrication properties of HFAE fluids are generally poor. The oil present in the fluid provides basic protection for lubricated contacts, but specially designed hydraulic components are usually required for use with these fluids. The lives of rolling element bearings within components tend to be short.
6.2.1.4 Corrosion protection
In order to ensure adequate corrosion protection, it is important that at all times the recommended proportion of the concentrate in the finished fluid be maintained.
6.2.1.6 Working temperature
The reservoir temperature of an HFAE system should not normally exceed 50 °C to avoid excessive loss of water. Lower working temperatures are preferred. The minimum working temperature is 5 °C to obviate the risk of freezing.
6.2.1.7 Fluid maintenance
Dilution of an HFAE concentrate should normally be with potable mains water unless the chemical hardness is particularly high, in which case softened or demineralized water should be used. Ideally, the properties of the finished product should be assessed by the supplier, with the water to be used by the customer for dilution, to ensure that the mixed fluid meets all the technical requirements.
As loss of water from the system is likely to occur over time, the fluid shall be regularly monitored to ensure that the concentration remains within acceptable limits. This is normally assessed by measuring the refractive index of the fluid. It is preferable that water lost through evaporation is replaced using demineralized water to avoid an increase in the concentration of salts in the fluid.
After extended use, cream, free oil, and residues formed from interactions between the hardness salts in the dilution water and the additives in the concentrate, can separate from HFAE fluids. Where significant phase separation occurs and free water can be observed, the cause should be investigated and rectified without delay.
The pH of the fluid shall be regularly monitored and maintained within the fluid supplier’s recommended limits.
The fluid should also be monitored regularly for the presence of microbiological contamination (e.g. bacteria, yeasts, and moulds). If left unchecked, high populations of microbes can shorten the service life of the fluid (e.g. by fluid destabilization and additive depletion), cause offensive odours, and present a health hazard to persons who come into contact with it.