rockman7892,
Too bad you are doing this now as opposed to a year from now; I might be able to share some real values with you. I am currently helping to implement a program at a large aggregate producer to accurately measure and record power consumption right down to each individual continuous load motor. There are aggressive energy savings programs in our area that require proving the reduction in consumption, which of course implies that you know the use under previous normal circumstances. We are installing a system of communications capable motor protection relays to continuously monitor them, but in the mean time, we have been doing preliminary observations as a way to justify the expenditure. Here are our initial observations, based solely on clamp-on ammeters compared to motor nameplate FLAs.
Crushers (cones, HSIs, Rollers etc.) tend to run at about 85 - 95% FLA, in fact most operators are monitoring crusher current as a way to maximize yield by controlling the speed of the infeed conveyors. I even once implemented a PID feedback loop on one where I looked at crusher motor current as the PV and infeed conveyor speed as the OP so the operator just dialed in 80 - 90% of the crusher FLA as the SP. I really wanted to use a belt weighing system as the PV feedback and use TPH as a setpoint, but it was all "too automated" for the operators (you probably know what I mean) and they went back to a manual system. But it was interesting.
There is a trend now to implement VFDs on VSI crushers as a way to tailor the output sizing, and if turned down, the power can drop significantly. But so does the TPH, so I would leave even those at 80-90% FLA for your purposes.
Stackers and inclines tend to run at or near FLA, in fact some even run into the service factor if they are telescoping and run out to their peak height. I attribute that to the motor selection software that is out there now and the fact that many OEMs are on tight budget constraints so they no longer leave that "fudge factor" in if they don't have to.
Under crusher and infeed conveyors tend to run at 70-80% FLA (less if there is a VFD), probably because NOBODY wants to dig one out if it overloads!
Overland conveyors are a crap shoot. My user stays conservative and wants the motors sized with that 25% fudge factor because unlike the stackers and inclines, changing out the motors is a bigger deal, usually out in a high traffic area where they have to shut down operations to let the riggers and electricians change out a motor. But I have certainly seen my share of those running close to the bone as well.
Screens tend to run around 70 - 75% FLA because most people apply standaqrd Design B motors to them and have to oversize them to get the necessary starting torque.
So all in all, I think for your rough budgetary guesstimate approximation, your process is sound, but not likely as conservative as you might think. The biggest problem with estimating energy usage in crushing operations only on motor loading only is what is called the "Recycle Rate" which does not show up as motor HP or kW, it only shows up as kWH. What I mean by that is, if more of your rock doesn't make it through the screen and goes back through the crusher again, you are expending energy to recycle and re-crush that rock. The crusher and return conveyor HP use remains the same, but the usable TPH is lower! That means then that your system has to run longer to finish the job, increasing your kWH. So in my opinion if you really want a conservative value, add about another 10% to your kWH figures to cover the recycle rate.
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