Inverter Features to protect pump ...similar to shear pins???
Inverter Features to protect pump ...similar to shear pins???
(OP)
We have an Inverter driven motor driving a pump through a 40:1 gear reducer box. We keep breaking shear pins in the coupling between the gearbox and pump.
Is there a fearture in a typical invert which would protect the equipment in a similar fashion as the shear pins? (Inverter is Allen Bradley 1336 Pluss II.
I suspect you would see a drastic increase in motor load (.i.e. current) just before the shear pins break. What happens is the viscosity of the product changes and becomes so thick that it prevents the pump from turning. Or sometimes a fairly solid chunk of product comes downstream and gets caught in the pump. In all cases I would rather have the inverter stop on a programmed fault of some kind instead of replacing the shear pins each time (sometimes 4 -5 times in a row before the bad product is eliminated).
CAF
Is there a fearture in a typical invert which would protect the equipment in a similar fashion as the shear pins? (Inverter is Allen Bradley 1336 Pluss II.
I suspect you would see a drastic increase in motor load (.i.e. current) just before the shear pins break. What happens is the viscosity of the product changes and becomes so thick that it prevents the pump from turning. Or sometimes a fairly solid chunk of product comes downstream and gets caught in the pump. In all cases I would rather have the inverter stop on a programmed fault of some kind instead of replacing the shear pins each time (sometimes 4 -5 times in a row before the bad product is eliminated).
CAF





RE: Inverter Features to protect pump ...similar to shear pins???
You can set this from 100% of the nameplate or FLC to upto 200% (for a short duration) of the FLC/Name plate current.
RE: Inverter Features to protect pump ...similar to shear pins???
RE: Inverter Features to protect pump ...similar to shear pins???
A month ago,I wouldn't think I would be sayng this.
Did you check the possibility of using a "Magnectic Coupling".They can be set for a given torque rate and stop transmiting torque everytime you exceed that rate.Once excess load is removed it will return to normal use on its own.I have not used one of these things myself,but I see where this technology can be a viable option.
Try their Website "magnadrives.com"
GusD
RE: Inverter Features to protect pump ...similar to shear pins???
RE: Inverter Features to protect pump ...similar to shear pins???
Hello J. Bartos.I am curious to know why you caution the use of Magnetic Couplings.Do you have any reason for your concern regarding these couplings?We have never used this particular technology in our plant,but the idea is intriguing nevertheless.
As for stopping the breaking of shear pins,it requires a positive braking system that cannot easily be provided by the inverter itself.PHASE reversal would probably act fast enough,but the cure may cause some problems to the system
itself.I believe that in this application, you have to have positive braking at the motor or gearbox.Rapid Inverter Deaccel. or Dynamic Braking won't solve this problem.
GusD
RE: Inverter Features to protect pump ...similar to shear pins???
CAF
RE: Inverter Features to protect pump ...similar to shear pins???
The type of pump, brake Hp of the pump, motor Hp, and VFD Hp rating would be very helpful.
The VFD, somewhat depending on size, may not be sensitive enough to protect the pump drive train from damage, lots of gear reduction and oversized VFD/motor I would bet. If you eliminate the shear pin, someone will program the VFD so that it will not "nuisance trip" and end up with a damaged pump. The shear pin is doing it's job, protecting the pump!
RE: Inverter Features to protect pump ...similar to shear pins???
Please go ahead & try. You will get the required info. in the drive manaul.
RE: Inverter Features to protect pump ...similar to shear pins???
RE: Inverter Features to protect pump ...similar to shear pins???
I'm guessing that if you stuck a wrench in the pump impeller, there's no electrical or electronic solution available that would be fast enough to keep the pin from shearing. The inertia of the motor/shaft would probably shear the pin even if power was disconnected.
I suspect that mechanical couplings would prevent the wrench from shearing the pin, though.
For smaller overloads, electronic methods would probably be helpful.
RE: Inverter Features to protect pump ...similar to shear pins???
CAF
RE: Inverter Features to protect pump ...similar to shear pins???
1. Flux or magnetising current
2. Torque producing current
Torque producing current is in phase with the voltage (resistive), while flux current lags the voltage (inductive).
I would suggest using one of the digital outputs to "At Torque". This could then be used to shut down the drive. You will need to enter a value in the "Dig Out Current" setting of the drive that is of an appropriate value (dependant on motor and load characteristics).
I have used this feature many times with success.
RE: Inverter Features to protect pump ...similar to shear pins???
Hello J. Bartos.I am curious to know why you caution the use of Magnetic Couplings.
///I just mentioned a word "avoid" in a sense of "option" rather than "caution." Incidentally, this Forum offers eng-tips.\\\
Do you have any reason for your concern regarding these couplings?
///There might be some as already posted by gannu0716 June 17.\\\
We have never used this particular technology in our plant,but the idea is intriguing nevertheless.
As for stopping the breaking of shear pins,it requires a positive braking system that cannot easily be provided by the inverter itself.PHASE reversal would probably act fast enough,but the cure may cause some problems to the system
itself.I believe that in this application, you have to have positive braking at the motor or gearbox.Rapid Inverter Deaccel. or Dynamic Braking won't solve this problem.
///However, the electromagnetic brake could with some mechanical side effects.\\\
GusD