MACHINERY LUBRICATION- INDIA NOVEMBER-DECEMBER 2019 | Page 18

PERSPECTIVE
SILICONES (SYNTHETIC)
POOR
MODERATE
BEST
OXIDATION AND THERMAL STABILITY
LOW VOLATILITY
as to achieve increased varnish or
deposit control, extended relubrication
intervals or enhanced lubrication
properties. Assess the pros and cons of
switching lubricants in terms of cost,
compatibility, change-out procedures,
etc.
HYDROLYTIC STABILITY
ADDITIVE SOLUBILITY
BIODEGRADABILITY
LOW-TEMPERATURE BEHAVIOR
HIGH VISCOSITY INDEX
SEAL COMPATIBILITY
LOW COST
MAXIMUM OPERATING TEMPERATURE
correct the root cause of the issue. New
operating conditions or the use of a
newtechnology may also be motivation
for
favoring
high-temperature
lubricants, along with simply desiring to
enhance performance for improved
reliability.
Lubricant Selection
The first step in the lubricant selection
process for a high-temperature
FLUID
Polyalphaolefins
(PAOs)
application is to estimate the average
operating temperature or temperature
range. At this point, a temperature-
control initiative may be implemented,
such as installing a heat exchanger,
insulant or additional ventilation. Also,
be sure the OEM requirements and
current machine conditions match the
lubricant’s specifications.
The
expected
performance
improvement should be specific, such
WEAKNESSES APPLICATIONS
High VI, high thermal oxidative stability,
low volatility, good flow properties at low
temperatures, nontoxic and compatible
with mineral oils Limited biodegradability, limited
additive solubility, seal shrinkage risk Engine oils, gear oils, bearing oils, com-
pressor oils, high-temperature grease,
lube-for-life applications
Low viscosities only, bad hydrolytic
stability, limited seal and paint
compatibility Compressor oils, high-temperature grease,
co-base stock with PAOs, bearing oils, gear
oils, oil mist, jet engine oils
Low VI, limited seal compatibility, not
miscible with mineral oils, moderate
hydrolytic stability Fire-resistant hydraulic fluids used in power
plants, factories, marine vessels, mining,
aircraft and mobile equipment
Excellent lubricity, nontoxic, good
thermal and oxidative stability, high VI Additives marginally miscible, not
miscible with mineral oils, limited
seal/paint compatibility Refrigeration compressors, brake fluids (water
soluble), fire-resistant fluids (water soluble),
gas compressors (low gas solubility), worm
and high-temperature gears, chain lube (clean
burn off), metal-working and quenchants, H1
food-grade lubricants
Highest VI, high chemical stability,
excellent seal compatibility, very good
thermal and oxidative stability Worst mixed and boundary film
lubrication properties, not miscible
with mineral oils or additives High-temperature fluids, specialty
greases, lubricant-contacting chemicals,
some brake fluids
Nontoxic, biodegradable, high VI, good
low-temperature properties, miscible
with mineral oils
Phosphate
Esters Fire-resistant, biodegrades quickly,
excellent wear resistance, scuffing
protection
Silicones and
Perfluoropoly-
ethers (PFPEs)
Please note that synthetics are not the
only suitable lubricants for high
temperatures. Mineral oils with strong
refining and additive packages may
work as well. Synthetic lubricants must
STRENGTHS Diesters and
Polyolesters
Polyalkylene
Glycols (PAGs)
To obtain the desired results, you may
need to be more specific in terms of the
lubricant’s technical properties. The
suggested parameters or attributes to
consider include the viscosity required
by the machine or components at the
operating temperature, the film
strength properties, the oxidation
resistance, the compatibility of the new
lubricant with the current lubricant as
well as with the synthetic materials in
the machine, the potential impact of
typical contaminants around the
machine, and any OEM or industry
standards.
16 | November - December 2019 |
www.machinerylubricationindia.com