Koehler K18325 / K18345 / K18347 Grease Mechanical Stability Tester (Roller Type)

Overview

The Koehler K18325, K18345, and K18347 Grease Mechanical Stability Testers (Roller Type) are precision-engineered instruments designed to evaluate the mechanical shear stability of lubricating greases under controlled thermal and rotational stress. Based on the standardized roller test principle—where grease samples undergo defined mechanical agitation inside rotating cylindrical drums—the instrument quantifies structural degradation via measurement of penetration consistency before and after testing (i.e., worked vs. unworked cone penetration per ASTM D217). This method directly correlates to real-world performance in bearings and other high-shear applications where grease thickener breakdown can lead to leakage, oxidation acceleration, or loss of lubricity. The system operates by subjecting sealed grease-filled test tubes to regulated rotation at either 10 rpm (low-shear simulation) or 165 rpm (high-shear simulation) within a thermally stabilized chamber, enabling reproducible assessment of structural resilience across industry-relevant temperature profiles.

Key Features

• Modular configuration options: single-, dual-, and quad-unit systems (K18325, K18345, K18347) support parallel sample processing while maintaining individual thermal and rotational control.
• PID-controlled microprocessor temperature regulation ensures rapid thermal equilibration and stability within ±1°C (±2°F) across the operating range—up to 93.3°C standard, extendable to 160°C with the optional high-temperature module (K18347).
• Dual-line LED display shows both setpoint and real-time chamber temperature simultaneously in °C or °F units, supporting laboratory-standard unit flexibility.
• Robust drive system featuring a heavy-duty motor coupled with interchangeable gear trains enables seamless switching between 10 rpm and 165 rpm without manual recalibration or mechanical reconfiguration.
• Integrated safety architecture includes automatic overheat cutoff circuitry that de-energizes the heating system upon exceeding user-defined thermal limits, plus physical protective guards over all heated and moving components.
• Thermally optimized enclosure constructed from insulated steel with durable polyurethane enamel finish resists corrosion and maintains consistent internal thermal gradients during extended operation.
• Uniform heat distribution achieved via 1200 W heating element paired with cast-aluminum axial fan, minimizing radial and vertical temperature stratification within the test chamber.

Sample Compatibility & Compliance

The Koehler Grease Mechanical Stability Tester accommodates standard ASTM D1831-compliant test tubes (including optional K183-0-1A and K183-0-4 accessories: stainless steel rollers weighing 5 kg, needle caps, and O-ring seals). Its design fully conforms to ASTM D1831 “Standard Test Method for Mechanical Stability of Lubricating Grease (Roller Stability Test)” and MIL-G-10924SA specifications for military-grade grease qualification. The high-temperature module (available with K18347) permits deviation testing beyond the nominal D1831 time/temperature envelope—enabling R&D evaluation of next-generation thickeners, complex soap formulations, or synthetic base stocks under accelerated aging conditions. All models support GLP-aligned documentation workflows when integrated with optional RS232 data logging and third-party LIMS platforms.

Software & Data Management

While the base instrument operates via embedded firmware with front-panel controls, optional RS232 serial communication enables integration with external PCs for automated data capture, temperature profiling, and audit-trail generation. When used in regulated environments (e.g., ISO/IEC 17025-accredited labs or FDA-regulated manufacturing sites), the system supports 21 CFR Part 11-compliant electronic records when paired with validated software solutions—ensuring traceability of test parameters, operator IDs, timestamps, and calibration logs. Temperature ramping profiles, dwell times, and speed transitions can be pre-programmed and recalled, reducing inter-operator variability and supporting method transfer across multi-site operations.

Applications

• Quality control of finished grease products against specification limits for mechanical stability.
• Formulation development of lithium, calcium sulfonate, polyurea, and clay-thickened greases.
• Comparative evaluation of additive packages affecting shear resistance and fiber network integrity.
• Accelerated aging studies assessing long-term structural retention under elevated thermal stress.
• Failure analysis of field-failed greases to determine root cause (e.g., thickener collapse vs. oil separation).
• Regulatory submission testing for OEM approvals requiring ASTM D1831 or equivalent military specifications.

FAQ

What standards does this instrument comply with?
ASTM D1831 and MIL-G-10924SA are fully supported; optional high-temperature operation extends test capability beyond these standards for research applications.
Can multiple samples be tested simultaneously?
Yes—configurations include single (K18325), dual (K18345), and quad (K18347) independent test units, each with autonomous temperature and speed control.
Is the high-temperature module factory-installed or retrofittable?
The 160°C high-temperature module is available as a factory-integrated option on K18347 units; retrofitting to existing standard units is not supported due to thermal and safety certification requirements.
How is temperature uniformity verified across the test chamber?
Chamber homogeneity is validated per ASTM E742 using NIST-traceable PT100 probes at nine spatial points; typical deviation is ≤ ±0.8°C at 93.3°C steady state.
Are consumables and accessories supplied with the instrument?
Standard delivery includes test tubes, roller assemblies, sealing components, and calibration certificates; replacement parts such as O-rings, needle caps, and calibrated thermometers are available under catalog numbers K183-0-1A and K183-0-4.