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D5275-20 – Standard Test Method Technical Guide
📐 Overview and Scope
The D5275-20 standard specifies the Fuel Injector Shear Stability Test (FISST) for measuring the percent viscosity loss at 100°C of polymer-containing fluids. This test evaluates the shear stability of polymers by passing the fluid through a diesel injector nozzle, causing degradation that reduces viscosity. Units are in SI, with allowances for PSI and HP in specific instruments.
| 🟦 Referenced Standard | 📏 Title |
|---|---|
| D445 | Test Method for Kinematic Viscosity of Transparent and Opaque Liquids |
| D2603 | Test Method for Sonic Shear Stability of Polymer-Containing Oils |
| D3945 | Test Method for Shear Stability of Polymer-Containing Fluids Using a Diesel Injector Nozzle (Withdrawn 1998) |
| D7042 | Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer |
⚠️ Safety: The standard does not address all safety concerns. Users must follow specific precautionary statements in Section 7.
⚙️ Test Method and Procedure
The polymer-containing fluid is passed through a diesel injector nozzle at a high shear rate. Less stable polymer molecules degrade, reducing kinematic viscosity. The percent viscosity loss at 100°C is reported, indicating shear stability. This method minimizes thermal or oxidative effects and is not intended for predicting field service performance across different polymer classes or lubricant formulations.
| 📐 Parameter | 🎯 Detail | ⚡ Condition |
|---|---|---|
| Shear Device | Diesel Injector Nozzle | High shear rate |
| Temperature | 100°C | Viscosity measurement |
| Reported Result | Percent viscosity loss | Shear stability indicator |
| Unit System | SI (exceptions for PSI, HP) | Standard practice |
💡 Note: This test method was originally Procedure B of D3945. Due to frequent differences with Procedure A, FISST was established as a separate test method.
❓ Frequently Asked Questions
🔍 What is the Fuel Injector Shear Stability Test?
It is a test method for measuring percent viscosity loss at 100°C of polymer-containing fluids due to shear degradation in a diesel injector nozzle.
💡 Why is the test performed at 100°C?
The viscosity loss is measured at 100°C to standardize the evaluation of shear stability under consistent thermal conditions.
⚡ What equipment is required for the FISST?
The test requires a Fuel Injector Shear Stability Test apparatus, including a diesel injector nozzle and viscometer for measuring kinematic viscosity.
📌 What standards are referenced in D5275-20?
Key references include D445, D2603, D3945 (withdrawn), and D7042 for viscosity measurement and shear stability assessment.