Cooling Water Control Boosts Production
PCT Engineered Systems of Davenport, Iowa, builds the BroadBeam brand of electron beam machines that can be used for everything from cross-linking plastics to drying inks, curing adhesives and sterilizing surfaces. Because the machines produce up to 350,000 V, the company uses a cooling water system to test the units before they are sold. Booming business led the company to expand its facility in 2013.
PCT's presentation at this year's Siemens Industry Automation Summit highlighted how the company used a new automation scheme to boost its production of electron beam machines.
With its expanding business, PCT found that its existing water circulation system couldn't handle higher the production rates because the unit was outdated, undersized and had only one water circuit. "We needed a reliable, automated system with a larger capacity that could supply enough water to let us test from one to 12 machines at a time," said Tim Riess, PCT electrical and controls engineer.
To address the problem, Riess said the company built a more advanced system that separates process water from cooling water, includes a water-to-water heat exchanger and features a sophisticated pump control system.
The process water circuit of the design consists of a 2,000-gallon tank, one low-volume pump and three variable-speed, high-volume pumps. The cooling water circuit has a 5,000-gallon tank, two circulation pumps and a 370-ton cooling tower. The two circuits meet int the middle at a large heat exchanger.
PCT's design used a Siemens controller with digital, analog and thermocouple signal modules, a 22-inch touch-screen HMI, ac drives to control the pumps, and motor starter controllers with voltage and current monitors, as well as soft starters.
Through Siemens' TIA Portal, the company programmed the HMI via its Step 7 V12 and WinCC Advanced V12 software, and the other components with Starter and Simocode ES software.
The control scheme has the individual water circuits controlled independently. PID loops control two of the process water circuit VFDs, ensuring that when the water demand from the manufacturing facility increases, the pumps provide more water, with the third pump acting as backup as necessary. Automatic control maintains process water at constant pressure.
For the cooling water circuit, automatic control maintains process water below set temperature. The operator interface for both main circuits allows changing of set points and other variables available on the screen.
The benefits of the new water circulation system include easy diagnostics via the PLC display, remote access to the HMI, and HMI networked data logging, Riess said, adding that the automated system requires little supervision and works so well that in addition to upping production, it let the company build an extra-large version of the electron beam machine.