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RBOT procedure to determine oxidation stability available from Particle Test

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article image RBOT procedure for determining oxidation stability

The RBOT procedure, available from Particle Test , employs severe oxidation conditions to determine oxidation stability. The RBOT procedure is suitable for both new and in-service oils, and is applicable to many types of petroleum oils. The sample is oxidised in the presence of water and a copper catalyst in a stainless steel pressure vessel under an initial pressure of 90psi (620kPa). Pressure inside the vessel is recorded electronically or mechanically while the vessel is rotated at 100rpm at constant temperature, and the amount of time required for a specified drop in pressure is the oxidation stability of the sample. A variation of the RBOT method is the ‘Thin Film Oxidation Uptake Test’ (TFOUT) for gasoline automotive engine oils.

Constant temperature bath rotates oxidation pressure vessels at 100rpm at an angle of 30° in accordance with ASTM specifications. The RBOT procedure includes drive system and oil bath with electronic solid state temperature control. It meets ASTM requirements for heat transfer capability and temperature control precision.

A carriage arrangement allows the oxidation vessels to be inserted quickly and securely in the drive system. A strong magnet holds the vessel in place while locating pins in the carriage engaging the base of the vessel. PTFE guides support the pressure vessel stem for stability. If the vessel becomes obstructed for any reason, the magnetic carriage releases it to prevent damage. A chain and sprocket drive system powered by a heavy duty capacitor start motor rotates the vessel carriages at 100rpm. Drive shafts ride on PTFE fluorocarbon bearings, which provide extended service and are compatible with silicone heat transfer fluids and other types of bath oils.

Bath temperature is controlled within ASTM specified limits by an electronic solid state controller with °C/°F switchable digital setpoint and display. Overtemperature protection is provided by a built-in limit control that automatically interrupts power to the bath when bath liquid temperature exceeds 16.7°C (30°F) above the temperature setting or 177°C (350°F). Power must then be manually restored by the operator after checking the cause of the problem. Pressure vessel carriage vanes circulate the bath oil during testing to ensure temperature uniformity, and an auxiliary stirrer can be operated between tests to prevent sludging of non-silicone bath oils.

The bath interior is constructed of welded stainless steel and is fully insulated. A hinged section of the bath cover provides easy access to the vessel carriages. Vapour barriers in the cover close around the vessel stems to contain vapours from the hot bath medium. A chemical resistant polyurethane finish protects the bath exterior and the control cabinet.

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