When examining efficiency in machine design, it is arguable that the human body contains some of the best-automated systems around. The circulatory system, for example, contains chambers and valves that efficiently direct and pump blood from the heart to the organs and the extremities of the body and back to the heart at a regular rate appropriate for production demands. Aside from operator error or the occasional faulty piece of hardware somewhere along the line, the fully automated circulatory system requires little to no maintenance to keep its production at sufficient levels. Moreover, it does so while recycling the same material repeatedly.
In the mechanical world of the manufacturing industry, many engineers seek the same clockwork-like regularity and effortless operation as seen in the human body. Okonite Co., based in Ramsey, N.J., which has been producing premium insulated wire and cable since 1878, has found such a method in a custom-designed pneumatic conveying system that “keeps the area clean, the powder contained within the system, and minimizes the amount of waste we have at the end of the day in this operation,” said Chris Wagner, director of facilities engineering at Okonite.
This particular operation at the Orangeburg, S.C., plant utilizes a proprietary three-step process to coat wire cable with super absorbent polymer (SAP). The SAP serves as a blocking agent so water cannot run inside the conductor if the insulation system of a cable or wire is breached in an underground or wet environment, such as in the utilities, petrochemical, and railroad industries.
While the fine powder is very responsive to moisture and effective at protecting wires, and therefore systems from shorts, in production it is prone to gumming up with exposure to moisture. Exposure of SAP to the humid air of South Carolina alone can cause clumping and, just like cholesterol buildup in a heart, can affect the efficiency of productivity.
A Focused Fix
The process at the S.C. plant runs between 400 feet and 600 feet (122 m and 183 m) of cable per minute through a 4-foot-long (1 m) atomizer chamber that blows the SAP around in a cloud that coats the wires. Prior to contacting pneumatic conveying manufacturers, an in-house system with a single-filter housing was used to capture product for reuse, but each time the filter needed cleaning, the chamber would switch from negative pressure to positive pressure. Powder would escape through the holes where the cable entered and exited the chamber and release into the plant atmosphere.
“When we contacted VAC-U-MAX, our goal was to make the system truly negative to reclaim the product and remove excess air,” said Wagner. “We needed to control the environmental end of the process and that is exactly what they did. It is a focused application.”
The dual conveyor system, supplied by the conveyor manufacturer, has an automatic changeover that works essentially like that of a pumping heart. First, cable enters into a chamber at about 400–600 feet (122–183 m) per minute while an atomizer simultaneously injects positive air and SAP into the chamber where it coats the cable fibers. At that same time, the dual conveyor system sucks air out of the chamber at a faster rate than it enters into the coating chamber, creating the negative pressure system where SAP cannot escape into the air external to the coating chamber.
At this point, the material enters into the first of two valved chambers for a number of seconds. After that specified period of time, the first valve closes while opening the second valve and chamber. When the first valve is closed, air is blasted into the filter to release any particulates to the bottom of the system where another routing system returns the SAP back into the hopper for re-use. This filtration cleaning process is repeated for a few seconds until the first filter is entirely clean, and then the second valve closes for its own identical process.
What seems like a complicated procedure is rather simple to an expert pneumatic conveying manufacturer. “We just told them how much powder we were moving, how much CFM, how much powder we were wasting on the over-spray and they put in a filter that was big enough to reclaim it,” noted Wagner.
Just as the efficiency of the heart includes the regular and economical re-use of blood throughout the cardiovascular system, so is the ideal in the manufacturing processes. In the case of Okonite, Wagner said, “we were losing about seven percent of our material per shift with our former system. The VAC-U-MAX system has brought that loss down to nearly zero.”
In addition to the dual conveying system, the conveyor manufacturer also supplied a bag unloading station to further eradicate moisture from the system and reduce the amount of SAP particles into the plant environment, slashing housekeeping time. Instead of releasing into the air, the unloading station now has enough negative pressure to remove the material before it has a chance to enter the air around the operator and become airborne within the plant environment. Because the powder is contained, the only protective gear the crew members need to wear are safety shoes and glasses.
“The bag unloading station that we have now does a much better job than before with not clogging up the powder in the system and it is healthier for the operators,” said Wagner. “It’s all integrated to this re-use system so it doesn’t go into a wasted dust collector; it goes into a re-use dust collector.”
Maintaining the health of a heart requires little effort save for the recommended occasional care for the muscular machine. Just as it is recommended that humans make sure passageways don’t get clogged by routine maintenance, the machinery in a plant should also require only routine touch ups.
Wagner explained that what little maintenance the system needs is made very simple by building a mezzanine above the coating chamber where the VAC-U-MAX system is housed. However, by implementing a fully automated system wherein the VAC-U-MAX system cleans its own filters, maintenance has become nearly non-existent. “The system works flawlessly and performance is maintained by following recommended periodical maintenance, just changing filters at recommended intervals,” he explained.
Maintenance of the relationship between the two manufacturers has also been without effort. “We ran a couple tests at their plant before they shipped it and everything worked as specified,” noted Wagner. “As with implementing any custom system, there were only two minor hiccups, and VAC-U-MAX handled them immediately. Everything they said they could do for us, they did.”