NPSHa is difference between suction pressure and vapour pressure of pumping fluid at that temprature provided by process engineer during pump sizing and NPSHr is provided by pump vendor. NPSHa > NPSHr to avoid cavitation due to vaporization of pumping fluid which is caused due to frictional loss between source tank to pump suction as a result suction pressure falls below vapour pressure and cavitation occur.
why NPSHr (from vendor) is have to be smaller than NPSHa (calculated by process engineer), shouldnt it be the higher the difference of suction pressure and vapor pressure, the less the cavitation will occur?
How about diaphragm actuators..say Shutdown valve air actuated where pressure inverse proportion to area applies...with less area force is more thereby u can actuate such a huge valve 30 inch valve too
I love the way you start to explain in simple terms then jump to trigonometry. Then you come back to simple terms and jump back to calculus. All over the spectrum with one brush stroke
Didn't get it can you elaborate? I understand that A increase by continuity equation velocity increase (Q= AV ) so by Bernoulli equation if total energy is constant and veleocity (kinetic energy) is increasing the pressure must be reduced so total E remain constant, inshort I understand a decrease, pressure decrease & vice versa a increase pressure increase (relatively) but I would like to understand by your pov @@mr.write1433
@core engineering : Sir are you sure that Area increase then pressure increase? If it is so than kindly answer that area of 8" pipe is higher or 6" pipeline . I am surprised that people are still comments nice explanation and all. What you explain is totally wrong. If area increase then pressure decreases that's all.
Don't get confused , simple thing is here …..according to Bernoulli's equation when we increase area so pressure will increase. For example we all use water pipe to give water in garden so In this situation we push a pipe so water will fastly go as far away, Hence when we push pipe it means we are decreasing area of pipe so pressure will decrease and velocity will increase.
@@Coreengineers Dear sir, Yes now you are correct that if area decrease then pressure increase. Kindly review your video because in video what you are explaining is totally Opposite. That's why I comment. Bernoulli equation is right and I am not confused but kindly check what you explained in your video. You will come to know that in video you explained wrong.
your point is right when considering a pressure of liquid at rest(P=F/A),but in motion always pressure is directly proportional to Area.(As per bernoulis Law)
But if at discharge, velocity is increasing then as per bernoulli eqtn the pressure will decrease at discharge, will it not cause back pressure sir....
No It'll not create back pressure as pump is used to increases the pressure of the fluid and at suction side we increase the dia because of cavitation prevention. For back pressure we use the nrv btw
What would happen if the suction line is smaller than the discharge line? Suction line is 3" and discharge of pump is at 2 1/2" but a reducer is used so it becomes 4".
I think that the NPSH is the sum of the pressure head and the velocity head in the suction of the pump minus the Vapor pressure of liquide .so this sum is still constant if we applie Bernoulli equation so the variation of npsh it’s from aspiration pressure losses that’s why we use bigger diameter to reduce the velocity only
