Cryosta离心泵基本原理演示文稿.pptVIP

21.10.1998 Basic Theory CP Basic Theory Centrifugal Pumps Definitions Lubrication Pump systems EIGA / IGC and CGA guidelines Performance Flow / pressure Efficiency Pump speed Pump curve Definitions The term centrifugal pump is applied to all types of pumps with an impeller having fixed blades housed in a suitably shaped casing, so that when the impeller rotates, momentum is applied to liquid in the pump casing transposing it from the inlet to the outlet side. To achieve this the pump casing has to be full off liquid. A centrifugal pump comprises an impeller and a casing together with a driving shaft. The point at which the shaft enters the ca-sing requires a seal. Sleeves, neck rings, wearing rings etc. are provided at the points where stationary and rotating parts are close together. The shaft requires journal and thrust bearings and a coupling from the driving unit. With radial flow impellers, liquid enters and discharges radially. The head developed is due to the centrifugal force extended on the fluid by the impeller. Definitions (cont’d) Centrifugal pumps can be either single stage or multi-stage. In multi-stage units, the total head is the end result of a series of impellers, all aligned within the one casing. Cryostar pump casings are radially split and the pumps can be horizontally or vertically positioned, they are non self-priming and have closed impellers (except C0 120). The major operating characteristics of a centrifugal pump are the Flowrate (Q), the Head (H), the Power (P) and the Efficiency (?). These characteristics are influenced by certain variables including the speed (N) and the diameter of the impeller (D). The parameter which classifies impellers according to geometry and operating characteristics is known as the specific speed. The value at the operating conditions corresponding to best efficiency is called the specific speed of the impeller. A centrifugal pump unit consists of: “Cold end” (the pump itself), one or more stag