ASTM D6022 Standard Practice for Calculation of Permanent Shear Stability Index

ASTM D6022 Introduction

Fluidity index modifiers are additives that are sorely needed in modern lubricant formulations, especially in the case of multigrade engine oils, gear oils, and hydraulic fluids. All such additives permit lubricant viscosity to be maintained over wide temperature ranges, ranging from excessive thinning at extremely high to thickening at low temperatures. Various mechanical forces acting during operation can break down these polymeric additives and result in viscosity loss and imbalance in lubrication effectiveness. It has been widely accepted in different applications – automotive, industrial, aviation, and marine.

ASTM D6022 Test Method

ASTM D6022 Equipment and Sample Preparation

Results and Interpretation

 The presence of low PSSI (0-10%) indicates that the shear stability is very excellent and that the lubricant is considered for increased high-stress applications where retention of viscosity is of great importance. A moderate PSSI (10-25%), on the other hand, implies some degree of viscosity loss that could probably hinder long-term performance, although such lubricants can still serve in many applications but will have to take relatively shorter drain intervals. The value of more than 25% in PSSI represents a clear and considerable loss of viscosity. It is a situation that renders the lubricant inefficient for long-term protection, especially in high or low temperatures and often under high load conditions.

Tests Related to ASTM D6022

ASTM D5275 measures viscometric loss using a sonic shear device whereas shear stability is analyzed with the Kurt Orbahn test in ASTM D6278. Kinematic viscosity is measured before and after shear testing in ASTM D445 to serve as a baseline in the calculations of viscosity.

Use of ASTM D6022 Testing in Various Industries 

PSSI Testing goes a long way in different areas, like the automotive sector, where oils must withstand many repetitions of shear forces over time from the engine to the transmission in addition to providing extended wear protection and fuel efficiency. Oils in industrial applications are hydraulic fluids and gear oils under extreme mechanical loads, such as internal gear pumps, where shear stability is vital for maintaining lubrication effectiveness. However, the aviation industry demands lubricants with enormous shear resistance whenever possible for safe operational performance in jet engines and hydraulic systems.

Materials Commonly Tested with ASTM D6022

The viscosity index test is particularly applicable for modified lubricity evaluation of lubricants formulated with viscosity index improvers such as multigrade engine oils (SAE 0W-20, 5W-30, 10W-40, etc.), applicable in both automotive and heavy-duty applications. Hydraulic fluids, which are predominantly used in systems for the construction, manufacturing, and aviation industries, also undergo relevant PSSI testing to ensure long-term reliability. Gear oils that go into the transmission systems, differentials, and input/output sides of industrial machinery must have a shear stability clause preventing perilous shifts in performance.

Common Challenges and Troubleshooting in ASTM D6022 Testing

Many factors can affect the accuracy of PSSI calculations. Rigidities are considered as the external conditions of shear tests, which include the pressure, temperature, or shear duration, and may lead to erroneous results if there exists any inconsistency among them. Hence, standardizing testing conditions reduces these discrepancies. Errors in viscosity measurement occur primarily from contamination of the samples and wrong calibration of the viscometer. Regular calibration of the equipment and proper handling of samples result in better accuracy.

Safety and Best Practices in ASTM D6022 Testing

Best practices guarantee safe and proper testing conditions. Proper care and handling of lubricants are important; laboratory personnel need to wear gloves, lab coats, and splash goggles to avoid contacting oils and additives. Instruments must also be calibrated regularly to ensure the accuracy of viscometers and shear test equipment.

Importance of ASTM D6022

The Permanent Shear Stability Index is considered the most important parameter for the evaluation of lubricants in terms of performance and durability. ASTM D6022 provides a harmonized method for determining the shear stability of lubricants, which can assist industries to develop and select lubricants without much concern for viscosity retentionistic degradation as time passes. The absence of viscosity stability brings premature wear and the mechanical failures that shorten the life of engines and appliances.