Process Improvement Boosts Sugar Production

Significant returns are beginning to flow as Imperial Sugar Company continues its process improvement strategy at its sugar refinery in Gramercy, Louisiana. Most recently, the focus was on white sugar refining.

With two days of training, a seven-member team comprised of Imperial Sugar employees embarked on five weeks of intense process improvement that would bring an increase in throughput of 10 percent.

Work began by recording centrifugal downtime and comparing actual cycle times against supposed fixed times.

Gramercy Centrifuge Throughput DMAIC team memebers included: (l-r)Byron Bailey, white sugar centrifugal operator; Nelson Rouillier, centrifugal mechanic; Kelly Salassi, instrument/electrical technician, River Parish Contractors; Mick Becnal, process manager; Erin Hymel, human resources assistant; Dennis Roper, remelt sugar boiler; Chris Caldarera, shift superintendent; and Ron Wagoner (not pictured), assistant process superintendent.

Before the centrifugal machines – a critical step in the sugar production process – do their work, sugar liquor is boiled and evaporated in vacuum pans to form sugar crystals. The resulting mixture of sugar crystals and syrup is dropped into a mixer and then periodically fed into the centrifugals, where the syrup is spun off to isolate the crystals for further drying.

A complete cycle consists of loading a centrifugal basket with about 19 cubic feet of the sugar-syrup mix, spinning and washing, and then plowing out the recovered sugar through a hole in the bottom. The fixed cycled time, which is supposed to run 70 seconds, was actually taking 90.

Initial findings showed the centrifuge process was running 10 percent slower than its listed capability, resulting in a loss of 10,000 cubic feet of sugar production a day.

“The team discovered the average cycle time was taking 20 seconds too long,” said Mike Becnel, Gramercy process manager. “When you take into account there are 13 centrifugals operating around 5,500 cycles a day, that 20 seconds starts to add up.”

The team identified and repaired a number of mechanical problems that were causing the increased centrifugal cycle times.

One key problem involved the mixer gates that open and close to feed each centrifugal with the syrup and sugar crystal mixture. The trouble was, after the gates closed, some of the syrup was still dripping into the centrifugal during run time, resulting in color and moisture problems. The excess moisture caused the operators to run the centrifugals longer than required.

Several other consequences followed because of the leaking gates. The excess moisture caused sugar to build up and clog the output hole at the bottom of the centrifugal basket. The plow that cuts and pushes out the sugar was taking longer to go down and would sometimes get stuck – all of which slowed the flow of sugar.

A couple of ideas put forth by the team effectively solved the problem.

First, the plant mechanics made and installed drip pans to divert syrup leakage from the gates during run time.

Byron Bailey, white sugar centrifugal operator, spray cleans with water the newly installed drip pan.

Second, the team designed and installed a hot water spraying system on the bottoms of the centrifugals to routinely clean the sugar discharge openings.

After running more tests, it also was determined that the process cycle time could be reduced without any adverse effects on the quality of the sugar output.

Many other solutions were implemented, involving a total of 103 action items.

At the end of the team’s work, average total cycle times were reduced in some cases by up to 9.6 percent.

Team member Ron Wagoner, assistant process superintendent at the Gramercy plant, said there was a time when he thought he knew all the problems and most of the answers. “I’ve been here 28 years, and in our process improvement efforts, we identified and corrected problems I didn’t know existed.”

When asked how she felt about the team’s work, Human Resource Assistant Erin Hymel said: “I was especially proud how a team made up of a diverse workforce came up with two unique solutions to a problem: the centrifugal spraying system and the newly installed drip pans.”

Centrifuge before newly installed spray system was installed, and after.

To help keep things running properly for the long term, a log sheet was developed to track what each centrifugal operator does per shift.

“I liked the way the team worked together. Everybody gave 150 percent,” said Becnel. “We were given the chance to make improvements in our area that needed to be done for years – improvements that resulted in immediate benefits.”

Becnel believes the same mindset that made these initial improvements possible will carry over into the team’s everyday work.

Imperial Sugar worked with Hagen & Co., using its trademarked “Control Factor Analysis” process that derives from a Six Sigma technique called DMAIC (Define, Measure, Analyze, Improve, Control).

Members of the white sugar refining DMAIC team were: Byron Bailey, white sugar centrifugal operator; Dennis Roper, remelt sugar boiler; Nelson Rouillier, centrifugal mechanic; Ron Wagoner, assistant process superintendent; Mick Becnal, process manager; Chris Caldarera, shift superintendent; Erin Hymel, human resources assistant; Kelly Salassi, instrument/electrical technician, River Parish Contractors. The team was mentored by Hagen Consultant Stephen Downey.