Grease Oxidation Stability Tester (Oxygen Bomb)

What is the Grease Oxidation Stability Tester (Oxygen Bomb)?

A grease oxidation stability tester heats grease films in a sealed oxygen-filled bomb and records the pressure drop over hundreds of hours. It shows resistance to oxygen uptake during storage or service, following ASTM D942, and helps compare base oils and antioxidant packages.

Overview

Five grams of grease is spread in a thin layer in each of five glass dishes stacked in a pressure vessel, which is filled with oxygen at 110 psi (about 760 kPa) and heated to 99 °C in a bath or block. A pressure gauge or transducer records pressure over time, with a decline indicating oxidation. Results are reported as pressure drop at specified hours, such as 100 and 500 hours, or as hours to a given drop. The test is long, so multiple bombs and continuous recording with alarm functions are useful. High-temperature variants run at 120 to 180 °C. Oxygen handling needs oil-free regulators and pressure-rated equipment, and bombs must be leak-tested before each run.

How does it work?

Grease is a dispersion of a thickener, such as lithium or calcium soap, polyurea or clay, in base oil with additives. Its behavior is non-Newtonian, so tests measure structure rather than viscosity. Consistency is measured by letting a standard cone sink into the sample for five seconds and reading the penetration depth in tenths of a millimeter, usually after working the grease in a standard worker. Dropping point is the temperature at which the first drop falls from a heated cup, indicating thermal limit of the thickener structure. Oil separation measures how much base oil bleeds through a wire cone under storage conditions. Oxidation tests heat grease in oxygen and record pressure drop, and water washout tests spray or immerse grease to find the percentage lost. Standard cup, cone and temperature geometry give comparable results.

What are the key features?

• Multiple oxygen bombs in one heating bath or block
• Pressure transducer with continuous data logging
• Safety relief and oxygen-compatible fittings
• Temperature control 99 °C standard, high-temp option
• Alarm for leak or excessive pressure drop

What are the technical specifications?

A typical grease oxidation stability tester (oxygen bomb) configuration offers test temperature of 99 °C (up to 180 °C option), oxygen pressure of ≈ 760 kPa (110 psi), sample mass of 5 g × 5 dishes, number of bombs of 1–8, pressure range of 0–1.6 MPa and pressure resolution of ≈ 1 kPa. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Grease Oxidation Stability Tester (Oxygen Bomb) is used in antioxidant additive evaluation, storage stability of greases and base oil selection for long-life greases. Across the wider Grease Testing class, laboratories also deploy it for grease batch quality control, NLGI grade determination and high-temperature grease development.

Which standards and certifications apply?

Relevant standards and methods include ASTM D217, ISO 2137, ASTM D566, ASTM D2265, IP 396, ASTM D942, ASTM D1264 and ASTM D6184. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Grease tests are sensitive to sample handling. Fill cups without air pockets, and bring samples to 25 °C in a bath before penetration testing. Keep cones and worker plates clean and undamaged, and verify penetrometer zero and cone mass and dimensions. Calibrate temperature sensors in dropping point blocks. For oxidation bombs, check pressure transducers and leak tightness, and treat oxygen with care: use clean, oil-free regulators and a ventilated area. Replace consumables such as wire cones and cups per the method. Keep grease waste separate from solvents, and record reference grease checks with certified materials to support laboratory accreditation.

How do I select the right Grease Oxidation Stability Tester (Oxygen Bomb)?

Select an oxygen bomb tester when grease specifications require oxidation stability over hundreds of hours. Choose multiple bombs for higher throughput. Specify the number of bombs, high-temperature capability, recorder type, oxygen-supply arrangement and safety features. For lubricating oils use rotating pressure vessel equipment instead.

How does it compare with other Grease Testing variants?

Choose equipment according to the grease properties in your product specification. Every grease plant needs a penetrometer and grease worker for NLGI grade, plus a dropping point apparatus. Formulators of high-temperature and long-life greases add oxidation stability testing. Storage and bearing-application tests such as oil separation and water washout support quality control and complaint handling. Consider whether the penetrometer needs automatic operation, full-scale or quarter-scale cones, and heating capacity for the dropping point block, which is often 260 to 400 °C for high-temperature greases. Check compatibility with the standard edition cited by customers, and whether consumables such as wire cones, cups and wheel bearings are available. In the RFQ, list methods, sample throughput and the thickener types tested.