Pump Flow

Looks like another person cheating on homework!!!

I know the answer because I've run centrifugal pumps the wrong way. I'm not going to tell you the answer out right but think about what is happening in the pump. Fluid at the eye of the impeller is thrown outwards by the centrifugal force of the impeller turning. This generates a lower pressure area at the eye thus drawing more fluid in. Now imagine the impeller has straight vanes. What do you think would happen? Now what would happen if the direction of the impeller where to change.

And hey presto you have answered your own question with the application of some logical thinking

There's no better teacher than experience. Why don't you try it out for yourself and find out? Oh, and please post the answer here. Better yet, post a link to a video of you doing it so that everyone here can learn (or be entertained).

Been there. 2 x 75kW inlet pumps to a clean water treatment works....

<...Reverse flow?...>

Is there a non-return valve in the line?

Who cares - the silly thing can only pump in one direction never mind what the direction of rotation.

hi ,i found this article which may help ..
(( When dealing with a centrifugal device - either a pump, fan, or compressor - the possibility of causing or provoking a reverse flow is sometimes present. And what I mean by "reverse flow" is that the normal direction of flow (i.e., from the suction piping - through the pump - through the discharge side of the pump and into the discharge piping) is reversed. In other words, the higher pressure existing at the discharge of the pump is allowed to overcome the lower pressure that is always present at the suction side of the pump. This is a situation that is always possible - if one allows it to happen. This is so because it is the primary reason for having a pump in the first place: we want to transport a liquid from a source of low pressure to a target that has a higher pressure. In the process of doing that, some unfortunate things can happen:

• The mechanical coupling that connects the normal electrical motor driver to the pump shaft may suddenly break and disconnect the pump from its driver;
• The electrical power source supplying the electrical motor driver may suddenly fail - causing a "black out".
• The pump may suddenly lose its suction prime - such as sucking air or a vapor, or "cavitating" (a phenomena where the pumped fluid is vaporized because it reaches its vapor pressure temperature and then suddenly collapses). The net result of any of these things is that the pump suddenly stops pumping for a while - which means that it stops generating a discharge fluid pressure to overcome that which exists at the target of its flow.

The result of the above is that the high pressure fluid existing in the discharge side of the pump will seek a lower pressure. If there is no check valve (a device called a "non-return valve" in areas outside the Western Hemisphere) in the discharge or suction lines, there will be a flow through the pump in a direction opposite to the normal flow (reverse flow). That is why almost all centrifugal pump installations have a check valve installed in their piping configurations. Some install a check valve in both the suction and discharge sides of the pump))