Nozzle Testing

Simple question - How much pressure do you need to drive water through a 17 mm hole at the rate of 16 litres per second. For a perfect nozzle, i.e.  C=1, the answer is 2600 KPa (or depending on your age and general disposition, 370 psi). But what if the particular hole and the approach to it, is not only not perfect, but perhaps has a C value of .53, which is what the textbooks talk about for a "re-entrant nozzle"

Then the pressure needed would be around 10,400 KPa ( 1500 PSI)

Our customer needed an accurate answer. We faced two main problems. Firstly we had to supply a pump which would provide the these sort of pressures, together with piping connections which would operate safely. Secondly, the test set up, which would run for only a few minutes, should be an economical mobilization.

The pressure needed would easily be achieved with a positive displacement plunger pump, but the flow of 16 l/s requires very large plungers. Our Union TX125 will get to 5000 kPa at this flow, but mobilization was felt to be a bit costly, and we were concerned about the effect of pressure pulsations .

We might have used one of our multistage high pressure pumps with 2900 rpm drive motors, but the electrical power requirement would be a problem, and we would need to refurbish the pump before attempting to operate at these pressures.

In the event we decided to use one of our diesel driven multistage pumps, which could provide the required head at diesel speed (say below 2000 rpm). The selected pump being a Weisse 200x150 – 4 stage radially split pump, with balance drum thrust control.

The engine to give the lowest mobilization cost was the Detroit 16V71T, with a rated output of anything up to 700 hp , to do a job, which we expected would need around 100 hp.The job was carried out to the customer’s satisfaction, and we have the impressive picture that goes with this story.

WHAT WAS THE ANSWER?

5200 KPa (750 PSI) C= 0.7 (note ,this applies only to the specific pipe/nozzle tested)