Page 69 - Fluid Power Engineering

46 Cha pte r T w o

2.2.15 Environmentally Acceptable Hydraulic Oils
Recent years have been marked by efforts to combat serious threats
posed by industrial pollution of our environment. Hydraulic fluids are
naturally included in these threats. They are utilized in large amounts by
excavating machines, bulldozers, mobile cranes, and other outdoor
equipment. An oil leak may result in considerable pollution of the sur-
roundings and ground water. Mineral oils are composed of relatively
stable hydrocarbon compounds, and are only very slowly broken down
by microorganisms in the environment. Thus, pollution by conventional
mineral hydraulic oils can disturb the ecological balance for long peri-
ods. This fact led to a growing interest in biodegradable products. Micro-
biological degradation is the process where by microorganisms, with the
help of oxygen, break down organic material and extract nourishment
from the decomposed products. The following are the basic specifica-
tions of commercially available and environmentally acceptable hydrau-
lic oil. It is a synthetic base oil designed to biodegrade to its natural
state when subjected to sunlight, water, and/or microbial activity.
ISO VG 32/46 Viscosity at 100°C, 7.3 cSt
Viscosity at 40°C 40.1 cSt Viscosity Index (VI) 149
Specific Gravity 0.965 Flash Point 256°C
Fire Point 282°C Pour Point −56°C
Biodegradability; percentage biodegradable within 21 days 80%

2.3 Classification of Hydraulic Fluids

2.3.1 Typically Used Hydraulic Fluids
The following are typically used hydraulic fluids:
• Noninhibited refined mineral oil
• Refined mineral oil with improved anti-rust and anti-
oxidation properties
• Refined mineral oil with improved anti-rust, anti-oxidation,
and anti-wear properties
• Refined mineral oil with improved anti-rust, anti-oxidation,
and viscosity-temperature properties
• Refined mineral oil with improved anti-rust, anti-oxidation,
anti-wear, and viscosity-temperature properties
• Synthetic fluids with no specific fire-resistant properties
• High water-based fluid (up to 20% combustible materials
+ min 80% water)
• Chemical solution in water (more than 80% water content)
• Water-in-oil, water droplets in a continuous oil phase (60% oil
+ 40% water)