Centrifugal screeners keep pace
with process changes at toll processor

Centrifugal sifters provide versatility and mobility needed for the constantly changing size reduction, blending, and screening services of large toll processor CTSP Corp.

Combination size reduction/screening jobs typically yield 97-99 percent of usable powder to CTSP customers. Mounting of the sifter on a frame with casters offers mobility between processing rooms.

The custom processor screens a variety of plastics and other materials in small and large volumes in conjunction with ambient and cryogenic grinding, jet pulverizing, blending and mixing. CTSP finds that centrifugal sifters, being adaptable and easy to move, best link with these frequently reconfigured processes.

Alternative large rectangular vibrating shaker screeners lack the flexibility CTSP needs, says Craig Davis, sales and marketing manager.

As a result, CTSP gains one-third more uptime compared to rectangular screeners, which is made possible by the Kason Centri-Sifter^® centrifugal screeners' mobility and quick screen changes. It takes CTSP less than 20 minutes to identify a problem and replace the unit's cylindrical screens. "This compares with more than one hour to remove and comb through 8-12 rectangular screens of a shaker type screener," Davis says.

Sifters' Mobility Improves Uptime
Mobility improves uptime as the toll processor mounts the 2'6" (760mm) high by 5' (1525mm) long sifters on stands with casters so they can be easily moved between processing rooms. Davis says a rectangular shaker screener, because of its turbulent motion, requires a heavy-duty steel stand that is impractical to relocate without a forklift and proper structural support.

Screen breakage, he says, is at acceptable levels. "When screening abrasive material, wear on the screens is always a factor with any screener, but the quick screen change time of the Kason centrifugal sifters keeps the average throughput rate of the process at a high level."

CTSP's size reduction and screening jobs typically yield 97-99 percent usable powder to the customer. In the Centri-Sifter separator, helical paddles rotating inside the horizontal cylindrical screen basket impart centrifugal force to the particles, propelling them continuously against and through the screen. By recycling the oversize particles discharging from the "overs" discharge spout into its grinding system, CTSP converts a minimum of 97 percent of the raw feed material to the specified size.

CTSP's Range of Work
CTSP performs a variety of work for the plastics, additives, food and pharmaceutical industries, and it repackages liquids and solids into containers ranging in size from bulk bags to small sample packs. Particle sizes range from 1 to 2000 microns. Throughput rates range from 20 to 2000 lbs/h (9 to 900 kg/h), depending on the number and type of processes being performed.

In one application, a wood derivative product was screened to remove particles coarser than 70 mesh at 1000 lbs/h (450 kg/h). CTSP processed approximately 700,000 lbs (320,000 kg) of the product with minimal screen breakage. In this process, a screw conveyor transported the powders to a centrifugal sifter for separation, after which the powder was packaged.

Another typical application involved milling plastic pellets and conveying them through a system that included a Centri-Sifter screener as the final screening step. A flexible screw conveyor deposited screened particles finer than 300 microns into a valve bagger at a rate of 400 lbs/h (180kg/h). The "overs" were recycled into the process.

Prior to production runs, the company runs trials to determine processing and screening characteristics. Equipment is then configured and adjusted, and operating protocols defined for optimum results. CTSP's quality control department analyzes samples of powders with particle measurement equipment to meet specifications.

Quality Powders through Sifters
Davis says, "Ease of changeover, ease of clean-out, mobility, and lower cost of screens allow CTSP to assure reliability in meeting customers' production requirements while saving $5000-7000 per year in labor and materials compared to rectangular screeners in the same application.

"As business grows, we need to be as efficient as possible to get the most out of our existing capacity." CTSP has expanded from 2 to 15 different milling operations in less than 3 years, and has installed a larger capacity Kason model YOB Centri-Sifter to classify up to 6000 lbs/h (2730 kg/h) of 500-micron powder, virtually doubling the capacity of the Centri-Sifter MO models currently used.