Hello everyone. Today, let's discuss a term that might sound a bit like a tongue-twister: Ash-free Anti-wear Hydraulic Oil.
Let's break it down first. "Anti-wear Hydraulic Oil" refers to hydraulic fluid designed to prevent wear-a concept familiar to most, as it is widely used in hydraulic systems. Its primary functions are power transmission, lubrication, rust prevention, and cooling. But what exactly does "ash-free" mean? To answer this, we must look at the two main types of formulations used for anti-wear hydraulic oils.
Ash-containing vs. Ash-free: What is the Difference?
Anti-wear hydraulic oils generally fall into two categories: ash-containing types and ash-free types.
The ash-containing type is also known as the "zinc-containing" type. Its primary anti-wear additive is Zinc Dialkyldithiophosphate-commonly abbreviated as ZDDP. This additive offers excellent anti-wear performance and is particularly well-suited for use in vane pumps. However, therein lies the problem: the zinc within the fluid can trigger electrochemical reactions with copper and silver components inside the hydraulic system. This process displaces the silver, leading to corrosion of the system's parts.
The ash-free type, conversely, contains either no zinc at all or an extremely low concentration of it (the industry standard typically sets the threshold at 0.03%; anything below this level is classified as ash-free). Instead, it utilizes ash-free additives-typically based on sulfur, phosphorus, and nitrogen compounds-to provide its anti-wear properties.
What are the Benefits of Ash-free Oil?
First, it protects components containing copper and silver. Many precision hydraulic systems feature silver-plated valves or copper-alloy parts; using zinc-containing oils can cause these components to corrode. Ash-free oils do not pose this risk. For this reason, ash-free hydraulic oil is also sometimes referred to as "anti-silver hydraulic oil."
Second, it offers superior hydrolytic stability. It is virtually inevitable that some moisture will find its way into a hydraulic system. Zinc-containing oils tend to decompose easily in the presence of water, generating sludge that can clog filters. Ash-free oils demonstrate much greater stability and resilience in such conditions.
Third, it provides excellent oxidation resistance and extended service life. Ash-free formulations possess superior thermal stability; they are less prone to forming sludge or acidic byproducts under high-temperature conditions, thereby extending the overall service life of the hydraulic fluid.
Where is it Used?
Simply put: whenever a hydraulic system contains copper or silver components, the use of ash-free oil is mandatory.
Specific applications include: precision hydraulic systems equipped with silver-plated valves, piston pumps featuring copper-alloy components, servo valve systems, and similar equipment. Additionally, ashless oils are frequently used in forestry, agriculture, and marine equipment-sectors where environmental protection standards are particularly stringent.
In Summary
Ashless anti-wear hydraulic oil is, quite simply, zinc-free anti-wear hydraulic oil. It sacrifices a slight degree of extreme-pressure anti-wear performance (compared to high-zinc oils) in exchange for safe protection of copper and silver components, as well as superior hydrolytic stability and oxidation resistance. If your equipment contains silver-plated or copper parts, do not hesitate-choosing an ashless oil is the right decision.
