Hello from India

[Supreeth]

What is the reason behind most positive displacement pumps have expanding cavity on the suction side and a decreasing cavity on the discharge side..? pl help clear my doubt :confused2:

 

[TBN Support]

Welcome to the forum. :welcome:

I'm going to move your thread over to where more people should see it. Hopefully someone can answer your question.

 

[2ndhalf]

Hello from USA... But I don't know the answer. But Welcome!

 

[pwright]

Welcome! I don't know squat about pumps but in googling your question I found this:

These pumps provide a constant flow of fluid at a given pump speed, regardless of the discharge pressure required. A pressure relief needs to be used with these pumps to protect both the pump and the process in which it is installed.

at this page.

This page and this page pretty much say the same thing.

So my take then is that specific configuration is about maintaining a constant rate of flow.

 

[KennyG]

In a well designed system, all types of pumps will have a larger suction pipe and smaller discharge pipe. The large suction pipe reduces the velocity and pressure (head) loss. Low pressure on the suction side will lead to cavitation (localized flashing of liquid to gas, i.e. water to steam) which will cause flow instability and potential erosion of pump internal parts. At the high pressure discharge, pressure drops are not so critical.