August 01, 1999
by Teresa Acklin
Molinos de Puerto Rico's modernization project boosts flour milling capacity while utilizing fewer staff.
By L. Joshua Sosland
By most standards, the original Molinos de Puerto Rico flour mill in San Juan was not antiquated when the company made the decision in 1996 to begin a modernization project. Built in the late 1950s, the original flour mill was technologically comparable to many in the United States. It is only when it is compared with the new completely automated mill that has replaced it that the original facility suddenly seems almost prehistoric.
Consider, for example, the bulk flour loadout system at the mill. At the original mill, built by the company's parent, ConAgra, Inc., in 1959, loading bulk flour into a truck took about two and a half hours. The process required the work of both a mill employee and the oversight of a mill supervisor, in addition to the truck driver.
By contrast, the mill's new system cuts an astonishing 97% of the time out of the process. The loadout system fills a truck in less than five minutes with only the briefest participation by mill operatives. In this “self-serve” system, the truck driver is handed a key by the milling superintendent who, from a computer terminal, allows the driver to fill his truck without any direct miller supervision.
The loadout system is by no means an isolated example of the facility's increased automation. Because the large majority of its flour is shipped in sacks rather than bulk, the original mill had a large staff manning its packing carousels. The new mill has reduced overall staffing at the mill complex by 66%.
Concurrent with the staff reductions and the mill modernization, the mill initiated a Hazard Analysis and Critical Control Point program that is unique in the flour milling industry (see related story on Page 13).
The decision to spend U.S.$20 million to build a new mill in Puerto Rico was not made lightly. When it comes to setting the bar high for justifying capital expenditures, ConAgra, Inc. could be said to have “written the book.” In the mid-1970s, following a wrenching corporate restructuring, the company declared a commitment to building shareholder value through a series of financial objectives, including a 20% after-tax cash earnings return on year-beginning common stockholders' equity.
The company's remarkable growth over the past 25 years has been credited in part to a discipline of making capital investments only when the company was confident it would be able to meet these criteria. More recently, the company has initiated Operation Overdrive in an effort to further improve its financial performance.
Yet, even against this disciplined backdrop, the company's decision to spend U.S.$20 million modernizing its flour mill in Puerto Rico could be called, using a popular expression, a “no brainer.”
In the modernization completed in 1997, Molinos de Puerto Rico cut its work force significantly while raising its flour milling capacity. In the flour mill alone, only three employees hold full-time positions.
Molinos de Puerto Rico has recently begun an expansion of the new mill that will raise daily milling capacity to about 500 tonnes (11,300 cwts) of wheat flour from the current 385 tonnes (8,500 cwts). No additional employees will need to be hired to run the expanded mill.
The original modernization project featured the construction of a completely new flour mill. The mill comprises six stories with 3,240 square meters of work space.
The large majority of the equipment was made by Buhler, Inc., Minneapolis, Minnesota, U.S., including the control systems using Siemens programmable controllers. Evergreen Builders, Inc., Neodesha, Kansas, U.S., handled the civil work and mechanical and electrical installation.
The lights out mill operates through the night with no operatives at the plant. When a sensor detects a problem at the mill, a designated operative who is “on call” is automatically paged with a message telling where in the mill the fault has occurred. Using a personal computer and modem, the miller can assess the situation.
“I can sit at my home and check the problem,” said Eloy A. Nieves, flour operation manager. Tapping into the mill software, the miller can handle a number of issues remotely. “In some cases, a sensor may become dusty and be tripped incorrectly,” Mr. Nieves said. “I can resume mill operations from my P.C.”
Mr. Nieves said that the system has worked exceedingly well, though soft wheat is usually avoided in the mill and cleaning houses at night because of a higher probability of operation interruptions from these wheat types.
The milling process begins with seven raw grain bins with 2,500 tonnes of capacity. The bins were part of the original mill, though new transfer systems and conveyors were installed.
The transfer to the cleaning house is fully automated. For instance, the milling superintendent will instruct the system to make a blend of wheat taking 45% of a batch from one bin and 55% from another, set the total quantity and note the tempering bin where it will be conveyed after cleaning. The milling superintendent can schedule a number of wheat mixes to move through the cleaning process in sequence.
The compact cleaning house begins with an aspirator to rid the grist of light material, followed by a Buhler Combicleaner, which combines four functions classifier, separator, destoner and aspirator. The device removes items such as corn kernels, large dockage or foreign materials and stones.
Prior to tempering, a Buhler infestation destroyer eliminates unsound kernels, which are then aspirated. A magnet is the final step ahead of tempering.
A Buhler MYFA monitor measures moisture of cleaned wheat and then automatically calculates tempering time to achieve desired moisture levels. “We generally temper hard wheat 15 to 20 hours,” Mr. Nieves said. “Six to eight hours for soft wheat.”
After tempering, a Buhler scourer MHXS and air recycling aspirator provide intensive cleaning of the surface of the grain before going to first break.
“Each of the cleaning devices operates with a different principle for its different cleaning activity,” Mr. Nieves said. “The Combicleaner saves space and money.”
Running through the mill's layout, airlocks and filters are on the sixth floor, sifters on the fifth, bran dusters and purifiers on the fourth, impact detachers for bran removal and more bran dusters on the third, roll stands on the second and more impact detachers, as well as lifters on the first.
The mill utilizes the Buhler MYRA system, an NIR on-line laboratory, which measures on a continuous basis to ensure that a flour quality is within targeted specifications for protein, ash, moisture, absorption, color and starch damage. “The miller can use this information to fine-tune the flour mix later in the process,” Mr. Nieves said.
The mill has 12 bulk flour bins of 90 tonnes each plus one 30-tonne bin for flour from the mill start-up. The blending plant mixes to customer specifications. The computer system maintains a data base of customer specifications so that the miller selects the product from a drop-down menu rather than inputting each specification each time. The database includes precise information on additives and their proportions.
“We usually will pull flour from a number of different bins to achieve our desired blend,” Mr. Nieves said. “This helps provide the customer with greater consistency than if all the flour came from a single batch.”
To continuously track the mill's operating performance, a system of on-line scales tracks raw wheat, screenings, bran, patent flour and clears.
The facility has 11 loadout bins that hold 20 tonnes of flour each two for family flour packaging, four bins for bulk loadout and five bins in the highly automated carousel packager.
Agitators manufactured by Great Western Manufacturing Co., Inc., Leavenworth, Kansas, U.S., are used for chlorine before flour bins are loaded.
Sensors located throughout the mill to gauge flow, levels and proximity are manufactured by Bindicator Co., Port Huron, Michigan, U.S.
While it is an issue anywhere, sanitation maintenance takes on added importance in a tropical climate. The new mill was built with sanitation in mind, Mr. Nieves said. The building has a very tight seal with no 90 degree columns where dust could gather. A specially controlled air system provides an added measure of security.
The mill laboratory is located on the first floor. “Its location there is no accident,” said Manuel Orlando Herrera, president. “It is very close to the loading station, control room and packing area, right in the middle of the action.”
Because of the on-line quality monitoring system, the mill laboratory functions more as a calibration center to keep the Buhler MYRA system in check. A primary device is a Percon Inframatic 8600, which checks for a large number of qualities in 20 seconds. The Percon, in turn, is calibrated through a number of other devices. A Thermolyne 1400 calibrates for ash and a Blue M Electric Co. oven calibrates moisture. The Leco FP428 does the same for protein.
Other laboratory equipment includes C.W. Brabender Instruments, Inc., farinograph and amylograph, a Perten Instruments, Inc., Falling Number #1800 and a Chopin device for starch damage analysis. A Fisher Scientific pH meter checks flour with chlorine. A Perten Glutomatic system checks for gluten qualities. The lab also contains a quantitative bromate testing set-up and a test mill.
The mill warehouse is 2,700 square meters and capable of storing 900 tonnes of flour.
Molinos de Puerto Rico produces a wide range of flour, including high gluten, French-type flour, cake and mid-protein for bread. The company also offers product for sweet dough, pizza, turnovers and artisan bread.
Its Especial 50 brand has 12.5% protein and is used by bakers in northern and central Puerto Rico who freeze their dough overnight before baking a practice that takes a toll on bakery flour, necessitating greater strength than would otherwise be dictated by the end products baked from the flour.
The San Juan facility's maize mill has a simpler layout than the flour mill, consisting of three roll stands, a sifter and two degerminators as well as filters, scales and other ancillary devices.
The mill grinds 136 tonnes of maize daily into three granulations plus hominy feed. The finest granulation, called farmacal, is purchased primarily by the pharmaceutical industry. Because of tax considerations, Puerto Rico has a disproportionately large pharmaceutical presence.
The maize mill has its own series of bulk storage and loadout bins as well as the packing carousel that is shared with the flour mill.
Molinos de Puerto Rico is part of ConAgra's Trading Division. All of the grain milled at Molinos de Puerto Rico is imported. Every three weeks, a 20,000-tonne barge arrives with U.S. wheat. The barge also contains maize and a range of feed ingredients that the company merchandises. The grain is shipped from the Paulina, Louisiana, port of the Peavey Co., another ConAgra subsidiary.
While the mill is new and current management has been there for less than 10 years, the complex is not without connections with the past. The miller with the longest tenure at Molinos de Puerto Rico is Luis Diaz, Mr. Nieves said. Mr. Diaz worked at the mill from the time it opened in 1959, and, while he is partly retired, continues to help in the transition in the new mill.
Pointing to Mr. Diaz making adjustments at the computer terminal, Mr. Nieves said the veteran operative is fully comfortable with the state-of-the-art technology. At the same time, Mr. Diaz teaches younger staff members the art of milling, Mr. Nieves said.
“Luis helped open both pages of Molinos de Puerto Rico's history,” he said.
L. Joshua Sosland is executive editor of World Grain's sister publication, Milling & Baking News.