Not only electrical, but...

[Strahan]

If I was going to design that system, I would probably use positive displacement gear pumps with DC motors.

Flow control could be acheived by using RPM sensors on each pump motor.

The sensors would produce input signals to a small PLC that would in turn supply a reference voltage for the DC drive(s) that operates the pumps.

Size the pumps for the maximum flow that you require, and let the PLC turn the motor(s) speed up or down according to a pre-selected ratio.

The positive displacement pumps will give you a accurate and consistent flow rate that is dependant on the pump RPM.....control the speed, control the flow.

Just a idea
steve

Sounds good but what happens when the pump fails may still be rotating but not pumping any fluid? IMO a flowmeter would be the most efficient and fail safe way to go here. yes more expensive but is the outcome worth it or not? Rosemount mag flowmeter either 4-20ma out to the PLC or pulse frequency out to a counter card. Use a modulating valve with a feedback positioner for precise operation. Within the PLC use the PID instruction for proper control.

 

[hillbilly]

Good idea.

I would however use AC motors and would count the rotations then compare and adjust.

I considered AC motors with inverter drives, which I'm sure would do the same job as the DC motors, and even cost less.....however....

Since I'm much more familiar with DC drives and their application....especially the speed control aspect....I would use DC.

That's why I said "If I was going to design that system".:smile:

"Count the rotations then compare and adjust"....exactly.

steve

 

[wallyworld]

I've found 2 sources that have packages all ready and many in the field. Both basically use a PD pump with variable speed controls for injecting the bio into the low-sulpher diesel. They meter both products (the diesel is pumped with a standard submerged pump in the diesel tank) and modify the bio diesel to obtain the correct blend. Both claim to have accuracy to less than 1%.

Thanks all.

I think Dresser Wayne is building a dispenser to do this.Not sure if its out yet or not?