Swing in the sugar crystallizer - Garlock 3-D Seal maintains vacuum and moves with the shaft.

Sugar production is a rather moving business. To crystallize the sugar, the syrup is heated to evaporate the water content. This process is best carried out in a vacuum, as lower process temperatures are possible and the risk of discoloration (burning) of the sugar crystals is considerably reduced. During crystallization a viscous slurry is produced. Agitators keep this slurry in motion so that the sugar crystals can grow.

A major global cane sugar producer approached Garlock with a very specific problem. Their crystallizer was housed in a three-storey building and comprised a 6.7 m long shaft with a diameter of 15 cm, with a support bearing at the bottom and a drive motor at the top. The system was designed so that the area where the shaft entered the crystallizer was sealed with a gland packing. The stuffing box packing allowed air to enter the system, increasing the risk of batch spoilage. The stuffing box contained seven PTFE packing rings. Maintenance personnel had to climb to the top of the crystallizer three to four times a week to balance the packing. This meant an increased safety risk for the personnel. Despite this work, the packing could not maintain the required vacuum.

Together with the customer, Garlock discovered that a mechanical seal would allow the system to operate in a vacuum. However, the shaft had a radial runout of 1.25 -1.27 cm. The objective was therefore to find the right seal that could maintain a vacuum and move with the shaft.

The Garlock 3-D Seal was the perfect solution. The Garlock 3-D Seal offers a combination of PS SEAL® technology to seal the rotary shaft without the need of external lubrication, a tight tolerance bearing to maintain seal concentricity on the shaft and a Garlock 214 PTFE expansion joint to allow the entire seal to "move" with the shaft.

The seal was designed to meet the customer's requirements so that it could be installed in the plant with only minor modifications. With this solution, maintenance times were significantly reduced. An inspection of the seal is now only required every year, unlike in the past when the seal had to be checked several times a week. The customer can also hold the vacuum pressure reliably and continuously.

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