Vacuum Conveying Fills a Void

Customization, automation and safety enhance its appeal

By Alan S. Brown, Contributing Editor

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Vacuum systems are relatively easy to maintain because they contain no moving parts. Over the years, vendors have solved many of the problems that once plagued the systems.

"I've worked in vacuum conveying for 17 years, and I can remember systems that workers had to whack to get product moving," recalls Piab's Wilson. "Now we have much better filtration systems and fluidizers to break up caked powders in hoppers. No one wants to have to babysit their system today."

Piab and other vendors also have made their systems easier to pull apart to service.

"Every aspect of our vacuum pump is modular, from the air shock housing to air ejectors. The average pump lasts seven years before it requires maintenance, and if something breaks or fails, you can replace just that component," notes Wilson. "It is designed so that even a small stature operator can take it apart. The parts are small and easy to lift. The only thing you need a tool for are three hex nuts," he says.

Hapman has made its filters easier to clean by shifting the filter door to the side of the housing from the top, where traditionally it's located. "It's safer because maintenance people don't have to get on top of a silo or hopper and remove the top cover with the filter attached. We can now put our filters right up to the ceiling," notes Grant.

IEDCO's Heller points out that many of these innovations — high reliability, easy maintainability, quick cleaning, and tight material containment — started in the pharmaceutical industry and spread to fine chemical and other manufacturers.

Piab has introduced a less expensive system specifically for non-pharmaceutical manufacturers that don't require the corrosion resistance of Type 316L stainless steel. "It's for companies that make food, neutraceuticals, spices and fine chemicals. Its ability to have a full open bottom valve gives it very high throughput," explains Wilson.

The new piFlow system (Figure 3) costs 40% less than a similar 316L system, he says. Savings stem not just from switching materials but also from use of a more basic control system and the need for less extensive validation. In addition, the system boasts fewer optional features (such as fluidization).

Hapman and some other vendors argue that using electric blowers rather than plant air (from large compressed-air systems) saves money over the long term. "Plant air is very expensive to generate, and vacuum conveyors consume a lot of it. While both systems are similar in price initially, over the long run electric motors are cheaper to run than plant air systems," says Grant.

Hayes disagrees: "Vacuum systems only use plant air when actually conveying material. They do not run continuously. When you are refilling your hopper, you can't stop and start an electrical motor without ruining it, so what do you do? You leave the motor running and purge the air through a bypass system. So you're paying to pump air into atmosphere.

"With a plant air system, I take a 10-lb slug to the hopper, stop, and discharge. When I discharge, I cut the airflow. What that allows us to do is reverse-pulse the filter to clean it out. So I'm cleaning the filters when I'm not pulling a vacuum.

"People say it costs more money for compressed air, but when it stops it costs you nothing. When you're running a motor, you have to run it all the time and that costs money," says Hayes.

IEDCO's Heller also cites benefits of plant air. "IEDCO's mantra is: 'We don't mess around with things that go around… We try and design rotating machinery out of the equation. Compressed-air-driven vacuum pumps have no moving parts and are easier to maintain." However, the company isn't rigid about only using plant air. "So instead of pushing compressed air down our customers' throats, we also provide rotary claw, or bush, pumps. We've actually fallen in love with them. They have very flat vacuum performance and they can pull nearly as much vacuum as a compressed air system… By offering them, we can provide more flexibility in how we configure our lines."

Plant air systems also are much quieter than electric pumps and are intrinsically safe.

Hayes likes to talk about reducing the risk of explosions. He points to the 2008 explosion at an Imperial Sugar refinery, where a spark set off sugar dust that had accumulated in the rafters, killing 14 workers, injuring 40 others, and totaling the facility. (See: "Dust Gets Its Due")

Vacuum systems not only reduce the likelihood of sparks, but also prevent product from leaking into the plant.

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