Zinc has long been used as an effective additive in hydraulic oils to prevent wear and oxidisation, but zinc-based hydraulic oil has often performed badly in some manufacturers’ tests for sludge formation. However, a new offering from Shell, a zinc-based hydraulic oil based on its gas-to-liquids (GTL) technology, has changed this by passing a number of industry tests.
Shell’s GTL technology is based on producing fluids from natural gas, rather than crude oil, meaning it is almost entirely free from impurities like sulphur, nitrogen and aromatics. In addition to making crystal-clear base oils for lubricant products, GTL technology can be used to make various products, including an alternative fuel that can be used in heavy-duty diesel engines without modification to lower hydrocarbon, NOx, particulate matter and carbon monoxide emissions.
The new oil was subjected to the Bosch Rexroth piston pump test (JCMAS P 045), which, under operational conditions, assesses a hydraulic fluid’s oxidation stability. Even after 2,400 hours of operation, the oil was within testing limits, which suggest the oil has serviceable life in excess of 9,600 hours.
When subjected to the 1,000-hour ASTM D4310 TOST test, Shell’s product was found to cause sludge formation well under the 200mg DIN limit for the test, and it even beat a zinc-free commercial multi-grade (ISO HV) synthetic hydraulic fluid.
The product also performed well in Shell’s in-house test for the formation of varnish, which can lead to pump failure and premature wear of significant hydraulic components, further supporting the value of GTL technology for zinc-based fluids.