Product category:
Drives, motors and power transmission, couplings, clutches
News Release from: Lenze-ACTech | Subject: MC3000 series meter
Edited by the Manufacturingtalk Editorial
Team on 06 February 2007
Metering and pumping at chemicals
company
Chem-Flow used the PID feature on AC Technology's MC3000 series meter to hold the desired setpoint based on feedback from the process.
The challenge was keeping a tight rein on what's being pumped through Chem-Flow's dispensing and mixing systems The PID feature in the MC 3000 Series allows a drive to hold the desired setpoint based on feedback from the process
This article was originally published on Manufacturingtalk on 31 May 2001 at 8.00am (UK)
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Variables such as pressure levels, liquid flow rate, and liquid level, are detected by a transmitter, which sends the signal to a PLC.
The feedback is then communicated to the variable frequency drive, which uses it to adjust itself to hold the setpoint.
Chem-Flow, based in Chicago, IL, and in business since 1958, is an engineering company that specialises in manufacturing chemical feed systems.
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They serve a wide range of chemical processing markets, each with different needs and concerns.
Customers often come to Chem-Flow with a hard-to-solve dispensing problem, or an unusual metering application.
In developing the most appropriate solution Chem-Flow will pay a lot of attention to choosing the right drives.
As VP of Operations, Henry Glick, explains, "When you're designing systems whose function is to perform precise metering, transferring and mixing of multiple chemicals, drives are obviously an intrinsically crucial component, and our customers need to take their performance for granted." Add the fact that the ingredients are often quite expensive and sometimes can deteriorate quickly, the need for error-free operation becomes even more important.
A malfunctioning drive can shut down a production line; an inaccurate drive will ruin a batch of product; a hard-to-operate drive affects efficiency, and the list can go on.
According to Glick, Chem-Flow has been using the entire range of AC Technology Corporation's drives, "We've been working with AC Tech's Michael Kenney, taking advantage of the company's willingness to retrofit drives and software in order to meet our needs to the last spec." As far as the technology itself, Glick particularly appreciates the capabilities he gets through the MC 3000 Series drive's PID (Proportional Integral and Derivative) loop.
"The PID lets our customers keep a tight rein on what's being pumped," he explains.
What is a PID Controller and what's its role in Chem-Flow's dispensing and mixing systems? The PID feature allows a drive to hold the desired setpoint based on feedback from the process.
Variables such as pressure levels, liquid flow rate, or liquid level, are detected by a transmitter, which sends the signal to the variable frequency drive, for comparison to the setpoint.
Process systems often require a system-controlled parameter, such as motor speed, to be able to react to variable situations in order to keep another system attribute constant - pressure, flow, temperature, etc.
A simple example is a metering and dispensing system that has multiple discharge valves.
For flow to be repeatable at each valve, the pressure in the supply manifold must be held constant.
If the pump supplying this system is powered by a drive, the drive speed will need to increase as valves are opened, and the drive speed will need to be reduced as valves are closed, in order to maintain a constant pressure in the manifold.
A means to meet this requirement is to use a "set point controller," where the pressure in the manifold is measured with a pressure sensor and this value is compared with a "set point" indicating the value that you want the pressure to be.
A set-point controller compares the set-point value to the actual value and generates a speed command to the drive to correct the variance or error.
The AC Tech MC3000 builds this set point controller function into the drive. Request a free brochure from Lenze-ACTech ...
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