We have here a two stage centrifugal pump, 157gpm capacity, at 995 ft head.This pump is in a water injection service supplying three streams, the flow is controlled via valves which are throttled to meet requirement.
The motor driver is 100HP.According to the pump curve this HP is sufficient for the pump, in fact the actual HP required is 85HP.
The problem is the motor is running above the overload (24.3 amps).This is baffling to us , the ammeter was checked,we did a shut off head test ....this was ok,so we ruled out the possibility of pump inefficiency, however on further opening of the valves ,the ammeter reading went as far up as 30 amps, flow went off scale.
What next...what are we not seeing??!!

A few possibilities occur to me.  Another post already mentioned verification of voltage.  At lower voltage you will get high amps.  There is also a chance that you lost one of the three phases to the motor.  A three phase motor with one dead phase will draw very high amps on the other two. The ammeter is probably only reading one leg.  Check the amps on all three legs.  They should be equal.  I assume you are indicating that you are still getting high amps at rated flow with all three flow paths regulated to the correct flow rate.  I would check the calibration on those three flow meters.  If the flow is actually much higher than you think, this would require higher amps from the motor. And in water wash service, there may not be any other indication of excessive wash water rate.  You might be able to verify total wash water if you can measure sour water flows collected downstream. 

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