New at Piping Design Central: 03 November 2002

A bunch of pump-related articles from Pump Magazine:

Steel Pipe
http://www.pipingdesign.com/steelpipe.html

Metallurgy - is 316SS Soft or Hard?

<<Why is stainless steel so good against cavitation? - if it were soft, wouldn't the imploding bubbles erode the material away at no time? The reason for such excellent resistance of stainless steel to cavitation is it work-hardening property.>>

Pumps
http://www.pipingdesign.com/pumps.html

How Does Pump Suction Limit the Flow?

<<One of the claimed advantages of the centrifugal pumps over positive displacement pumps is their ability to operate over a wide range of flow. Since a centrifugal pump operates at the intersection of a pump curve and a system curve, by varying the system curve the operating point of the pump is easily changed.>>

Relief Valves for PD Pumps - Internal or External?

<<Positive Displacement pumps are knows as "flow generators", while centrifugal pumps can be thought as pressure (or head) generators. It is easy and convenient to control the centrifugal pump with a discharge valve: it changes a system curve, resulting in pump operating at different flows (see Article "How does pump suction limit the flow?"). Not so for the positive displacement pumps. All types of a PD pump (piston, rotary gear, lobe, vane, etc.) have a major similarity, which distinguishes them from the centrifugal pumps: PD pump curves show that they produce almost (depending on viscosity and internal clearances) the same flow, regardless of the differential pressure.>>

Pump Out Vanes

<<The main reason to use pump-out vanes (POV) is to change the pump axial hydraulic thrust. The rotation of the impeller results in "dragging into rotation" of the fluid in the gap between the impeller and casing walls. This is similar to a motion of a teaspoon in a cup, or a disk spinning inside containment. The resulting motion is referred to as "forced vortex"
.>>
Received on Sun Nov 03 20:57:00 2002