Tech Tip 7: Rotary Pump Maintenance – Oil changes and Use of the Ballast Valve

Most GC-MS vacuum systems comprise of a two-stage pumping arrangement - an initial low-vacuum, high capacity stage consisting of a rotary oil pump or diaphragm pump; and a second high stage, low capacity vacuum pump such as a diffusion or turbo-molecular pump.  The first stage or low-vacuum pump requires maintenance to ensure optimum pumping performance.  Two aspects that are often overlooked are the use of the ballast valve on the vacuum pump and replacement of the pump oil at the correct intervals.

Tech Tip 4: Random loss in sensitivity of injected samples through a batch

Most problems that occur in Gas Chromatography either gradually increase in severity over time or suddenly become a large issue, preventing further analysis by the instrument.

Random problems occurring infrequently are often ignored for long periods of time as the sample is simply re-analysed and the results are correct the second time. The problem itself can be hard to track down to determine the cause and then to provide a fix, as it isn't a continuous problem.

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