By Jim Montague, Executive Editor
Lots of jobs are harder than they first appear. Most look simple from a distance, but snags emerge as you get closer and actually try to do them.
For instance, washing the gleaming, silvery tanks on the trailer trucks that deliver all kinds of liquid products might seem relatively straightforward. However, liquid sugar is a lot less viscous than corn syrup, and so sugar is easier to clean off the inside of these tanks than syrup. In addition, temperature changes also make it harder or easier to scrub the tanks depending on the season. Naturally, thick syrup and cold weather are a nasty combination. And, while the saying "slower than molasses in January" is well-known, the real experts also know it's more difficult to clean tanks that have been filled with it, especially during the winter.
One company that deals with these issues all the time is L&S Sweeteners Co. (www.lssweeteners.com) of Leola, Pa., which manufactures and hauls a variety of sweeteners to its many customers. To keep up with demand and deliveries, L&S has to clean and sanitize a constant stream of tanks on shipping trailers moving through its wash bays (Figure 1). The core of this clean-in-place (CIP) process involves boilers and pumps that feed a 360° rotating spinner that sprays the inside of the tanks with 185 °F water for about 15 minutes, though higher temperature and time profiles are sometimes performed to meet the requirements of particular customers. This FDA-approved CIP process also includes a series of water rinses at pre-determined times and temperatures to ensure the removal of any residual product and the sanitization of the trailer's interior. The whole cleaning and sanitizing process used to take more than 1 hour.
Figure 1: Tanker trailers at L&S routinely need their insides washed and sanitized before being filed with a variety of sweeteners for shipping, but more viscous sweeteners and cold weather can make this difficult."What we really needed was a different CIP program for different customers and products," says Brant Widrick, L&S's quality control supervisor.
New Controls, New Interface
The company's former CIP system and operator interface included an elderly PC running an old DOS-based operating system, while the wash bay controls consisted of an outdated PLC. L&S reports that these controls could do little more than turn the boilers and pumps on and off.
"The existing wash bay system was outdated and getting difficult to support. Programming changes were impossible to manage. It was decided that modernizing the wash bay controls would help attract new business by instilling more confidence in L&S' capabilities," says Jeffrey Itell, sales engineer for Cemtech Energy Controls Inc., which represents Yokogawa Corp. of America (www.yokogawa.com) in L&S' area of Pennsylvania.
Consequently, L&S worked with Cemtech to implement Yokogawa's FA-M3 programmable logic control (PLC) system in its wash bays. The system also includes three of Yokogawa's EJA 530 pressure transmitters for tank level measurement, two RTDs to check supply and return temperatures, and two UM 330 temperature indicators to provide both signal conditioning for the RTDs and give operators a local display of those process temperatures (Figure 2).
Meanwhile, Iconics' (www.iconics.com) GraphworX32 software was chosen as the HMI for the FA-M3 system. It enables operator control, storing of wash data to a database and production of wash tickets for the drivers' records. GraphworX32 also performs the following functions:
- Offers password protection for the operators.
- Generates a wash ticket when a wash cycle is done.
- Generates a circular chart attached to the wash ticket.
- Allows the operator to perform a wash in manual mode.
- Gives operators the ability to reprint a wash ticket.
- Allows operators to select a custom wash procedure.
- Uses Microsoft Access to store all ticket data.
- Allows custom wash cycles based on seasonal changes and clients' requirements.
"Both Yokogawa and Iconics offered technical assistance to aid in developing this application. FA-M3 PLC offered a simple interface for communicating to Iconics' HMI software. The configuration was no fuss, and the documentation for communications was easy to understand and implement," says Itell. "Iconics has a strong commitment to being Microsoft-compatible, and this made Iconics a better choice because L&S needed to interface to other Microsoft software. For this application, Microsoft Access was chosen as the database for handling all information."
Customizing with Sequential Batch
To fulfill its desire for different CIP programs that would enable it to run customized wash cycles, L&S and Cemtech also decided to develop a sequential batch program using Microsoft Access as its core element and based it on principles in the ISA's S88 batch standard.
"Over a couple of years, L&S kept coming up with slight changes to its wash bay program, which required altering the PLC program, but they didn't have a staff engineer to do it every time someone wished to try something different," explains Itell. "However, L&S was very comfortable with Microsoft Access, so we needed a way for L&S to use Access to generate programs that could be executed in the PLC."
After examining the wash bay application more closely, L&S and Cemtech decided it fit the description of a sequential batch application because it also has steps that that were executed based on a time or an event. "All that was needed was a way to send a request written in Access to the PLC," explains Itell. "This was done with a Visual Basic (VB) macro in the GraphworX software. Iconics makes it easy to write VB modules that integrate with the HMI."
Consequently, Access was used to create the sequential batch program by first entering segment times, output states, inputs and logical events into a software table, and saving these entries as a unique database with a folder on the operators' computer. They can then select from all programs in that folder which program they wish to download to the FA-M3 system. Once downloaded, the program will be executed until a different program is downloaded.
Also, when a wash cycle is finished, a wash ticket is generated. This records completed washes and serves as a record for billing. GraphworX's HMI also generates a circular chart showing a trend of the supply and return temperatures to provide proof of sanitization of the tank.
"Now we can do it ourselves. We can add CIP recipe changes right on the PC in the Microsoft Access database, rather than calling our Yokogawa rep every time we need to change our software programming," explains Widrick. "For example, we can do a separate CIP program for heavy corn syrup that extends the pre-wash stage.
Previously, we had to do two full washes, so just extending the pre-wash saves a lot of water, energy and time."
Gains Secured, More Coming
The first major improvement that L&S gained by using FA-M3, GraphworX, Microsoft Access and its sequential batch program was that individual tank wash cycle times were reduced to about 40 minutes per trailer, so it can now complete 10 to 20 wash cycles per day. In fact, cutting wash times by 50% saved about eight hours per day, or a whole shift, in labor costs.
Besides saving time, L&S also learned that its FA-M3 and GraphworX system could help it save energy, too. For example, L&S uses its flexible CIP programs to adjust boiler performance. "We used to keep the boiler running for a whole 15-minute cycle, but the trailer tanks are well insulated and retain heat. So we realized we could maintain the required water temperature, but use the CIP program to turn off the boiler 10 minutes earlier than before, and save about 33% on our energy costs," adds Widrick. "Because we could play with the software and see how our process was working, we also found that we only needed 10 in. of water in the tanks, instead of 40 in., and this is saving a lot more water and energy."
Because of its success in the wash bay area, L&S is looking at using its sequential batch program in its blending department to help automate its sugar blending application.