Modern sieves slash changeover downtime

Switching to modern sieves can cut product changeover downtime by 300%.

By Del Williams

In processing industries where products share production lines, speed of product changeover can make the difference between healthy and not-so-healthy margins. In the quest for greater margins, no processor can afford excess downtime at product changeovers. Nor can they afford excess labor to clean and maintain cumbersome, outdated machines. Yet to avoid cross-contamination, especially in bulk powder applications, no corners can be skipped. That's why streamlining the production process from input to final product screening can be critical.

When a coatings processor avoided a production bottleneck by upgrading to a new sieve technology, it saw product changeover accelerate, with rapid payback that added to the bottom line.

"We cut downtime from product changeover by a third and enhanced product quality by switching to the Russell Finex Compact Sieves," says Bob Minton, maintenance manager at Deloro Stellite's coatings operations in Goshen, Ind. "By expediting cleaning, preventing cross-contamination and aiding product quality, we achieved ROI on the compact sieves in a few months."

A need for speed

Deloro Stellite is a global provider of solutions to industrial wear problems where heat, corrosion and abrasion can limit component life. It produces proprietary metal alloys from cobalt and nickel, which have metallurgical and physical properties suited to industrial wear challenges.

At its coatings operations, sieving was a critical process because the size of powdered metals controls its flowability into customers' weld points in a range of applications. To streamline production and enhance quality, the company planned to add a new sieving process for all initial powder inputs and final powder products at its Goshen, Ind., plant.

The company used traditional sieves for lower volume powder classifying, but Minton felt traditional sieves were too slow and complex for Deloro Stellite's current needs.

"With 5,000 product variations, we'd have to take apart each sieve, clean it and put it back together 10 to 12 times a day," explains Minton. "We needed a sieving technology that was easier to use than the same old type that's been on the market for 40 years."

The traditional sieves were cumbersome to work on, take apart, clean and put back together. And if the seals weren't aligned properly, they could leak, potentially ruining a product batch.

"Band clamps wore out, bent, broke or cracked, and the seal had to line up all the way around the flange," says Minton. "It took two people to work the seal around large diameter units, with no alignment pins or guides."

Fine powder sometimes worked its way into the clamp bolt threads on these traditional sieves too. When this happened, the sieve operators would call maintenance to have the bolt cut off and replaced with a new one. Maintenance was also called whenever sieve vibration adjustments were needed. All this added to production downtime.

At a bulk powder processing show, a traditional sieve supplier promised to show him an assembly shortcut, but was unable to put the unit back together. Minton decided he'd had enough of traditional sieves. He began a search for low-maintenance units to streamline the production process.

Speed delivered

Minton turned to a compact sieve from Russell Finex of Pineville, N.C.. The unit's design and ease of use impressed Minton, who felt it would expedite product changeover and improve bulk powder processing. A trial proved him right, and now there are four compact sieves at the Goshen plant.

"One operator can take apart and put together a compact sieve in less than a minute with no tools," says Minton. "Just undo four latches by hand, lift the top off, and then lift the screen out. To assemble it, reverse the process. It seals perfectly. Because the screen drops into a recess, there's no chance of misalignment; and cleaning is easy with a vacuum line."

"Everything's right there, easily accessible," says Minton. "Pop a cap off the end of the motor and there are your vibration adjustments. It's so easy to do adjustments that one of our junior process engineers realigned it. We showed him once, and he was comfortable enough to make the adjustments himself."

Minton estimates the new sieve technology saves about an hour a day in production downtime, compared to the cumbersome product changeover process required by traditional sieves. Product output and quality are also improved.

Traditional designs incorporate a spring-mounted base and a custom motor with a pair of eccentric weights at the end of the motor shaft. However, this design lacks accuracy in controlling the force of vibration imparted to the mesh screen, and is typically limited to a speed of 1,200 rpm.

In contrast, these sieves omit the need for springs and instead use a rubber suspension system. Combining this with a high-speed, 1,800-rpm vibratory motor and easily adjustable weight system allows much higher forces to be transferred through the mesh screen itself. This creates a more finely tuned and vigorous action, raising sieving efficiency.

"The adjustable weight system makes it easy to set the machines up," says Minton. "It helps us get the right time on the screens to get every bit of powder possible, while minimizing product loss to oversize."

The design of these sieves can go a step further to increase throughput by using the Russell Vibrasonic deblinding system in conjunction with the screen. By energizing the wires of the screen mesh with an ultrasonic vibration, the friction between the product and the screen is effectively removed. Mesh “blinding” is eliminated, helping to move material through the screens faster.

Because the sieves are crevice-free and constructed from polished stainless steel, including their stands, all surfaces are easily cleaned.

"The compact sieves make it easy for our operators to quickly and cleanly complete product changeovers without tools," says Minton. "They help with output, product purity and product loss. Saving even one product batch from possible cross-contamination could pay for the cost of the sieves. With the new sieves, our customers get a better quality product and better deliverability in the long run."

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