Is there any technique to check whether a gear pump is fully primed or not before operation?

Sir, if the pump was old, I recommend checking clearances between gears and gaskets. If not, you maybe face a cavitation problem. The first step is to diagnose the pump for noise, capacity loss, and pitting are three major indicators, but also let’s you know what your true NPSHA is. Install a compound gauge (one that measures both vacuum pressures as well as light positive gauge pressures) into the suction port of the pump or as close as you can in the suction piping. When the pump is running, the reading from this gauge will be equal to your NPSHA, less vapor pressure. If after subtracting vapor pressure this value is less than the pump’s NPSHR, you have confirmed that this is a cavitation problem. Installing a booster pump will raise the suction head for sure to solve this issuebut always remember it's not a good solution for the gear pump's total efficiency.

for the sake of pump noise you have to open the pump and check the clearance between the gears and adjust the tolerance of the gears thay might be too conjusted or too far so they cannot making required pressure and producing sound.

When your pump is fitted. Fill it with hydraulic oil. Then insure your suction line is full when fitted. Thats the only andsafest way. Gearpumps can not take a lot of punishment. When it keeps making a sound you should put on a flowmeter and check the flow against working pressure.

If your system pressure is200 bar the pump should deliver a certain amount of flow depending on cc of pump.

first of all PD pumps dosnt required priming first they pumped out air then suc fluid and pumpedout make sure suction line should sealed properly and dont take air.

noisy gear pumps is a headeach, idea of flow meter on del will definately help, realease air from suction vent .for less pressure check port gaskets and valve seat, valve seat gauging /surface making will help.

teeth clearances will be indicative with oil leakage