โ Scribed by O'Hanlon, John F.
No coin nor oath required. For personal study only.
Pumping speed is a quantity few of us measure. We are usually content with published data; however, we should know how speed is measured, so that we can meaningfully interpret data. Pumping speed is measured by established, standard techniques. Recommended practices have been improved; however, much data taken in old test domes pervades the literature. We should know the accuracy of the available data. We may also wish to measure the pumping speed to check for proper pump operation, or to provide specialized information. For example, the pumping speed may be needed for a specific gas, pump temperature, or pump fluid. If we know the correct pumping speed at the inlet of a pump and the correct connecting conductance, we can calculate the pumping speed at the chamber entrance with reasonable accuracy.
We begin by defining pumping speed and then describe its measurement in mechanical and high vacuum pumps. We include a simplified technique for checking an operating system, and we discuss the measurement of water pumping speed in high vacuum pumps. We conclude with a discussion of the errors inherent in standard test fixtures.
Pumping speed is the volumetric rate at which gas is transported across a plane. In mathematical terms speed is the gas throughput divided by the pressure at the plane of the pressure gauge.
๐ SIMILAR VOLUMES
In this chapter we review the operation of five low vacuum pumps (the rotary vane and piston, scroll, screw and diaphragm pump), and two medium vacuum pumps (the lobe or Roots pump and the claw pump). Vane and piston pumps are widely used for backing high vacuum pumps and for initial chamber evacuat
Organic fluids are used in rotary vane, piston, screw, scroll, lobe, turbomolecular, and diffusion pumps. In a rotary vane or piston pump fluids provide a vacuum seal between the moving surfaces and lubricate and cool the low-speed bearings and sliding surfaces. Screw, scroll, lobe, and turbomolecul