Cementing a Relationship

The wet cement process offers a challenging set of applications for centrifugal slurry-handling pumps. Solids are crushed in rod mills, then mixed with water and viscosity-controlling chemicals during the initial processing, which results in heavy solids contents of 60 percent and greater. Mill discharge is similar to other processes: The slurry is sent to an oversize control screen and on to holding tanks to feed continued processing into the dry product known as "Portland cement."

GIW pumps were first installed at a Northeastern Mississippi cement plant that was experiencing high maintenance costs and inefficient movement of slurry with a competitor's pumps. The competitor's design utilized a centrifugal seal consisting of multiple moving parts. The design was unfriendly to the maintenance personnel involved in keeping the plant process running smoothly.

The first installation for GIW was the replacement of a slurry transfer pump. GIW installed the new pump on one of the holding tanks receiving product from the grinding circuit. Solids were maintained at 68 percent, and the tank was used to feed other, smaller holding tanks downstream, which ultimately fed the rotary kilns.

The existing pump in this case had a 200-horsepower motor and was continuously drawing more than 55 amps. In addition to the high maintenance issues, the existing pump would not remove slurry from the feed tank below an eight-foot level. This flaw led to a huge deposit of dewatered solids that formed a small mountain in the center of the tank and eventual blockage of the discharge piping and tank shutdown. To put the tank back into service, plant personnel had to perform several steps to remove the solids.

The cement company selected a 12x14LCC28.4M pump as the replacement. The installed model utilized the existing 200-horsepower motor and a side-by-side v-belt–driven configuration. A duty point of 6,000 gpm at a discharge pressure of 28 psi set the pump operating very close to its best efficiency point.

Because the pump was in a transfer duty, it was not imperative to meet a particular flow rate, and this fact has contributed to the outstanding performance of this equipment. Suction performance of the LCC has enabled the plant to effectively pump down the feed tank until the level falls below the inlet piping, which is only a foot above the floor of the tank. This improvement has led to a huge savings in reduced tank downtime and lost product from the removal of the mountain of solids in the center of the tank.

Startup of this pump was without incident. Although it seems that most startups require at least some adjustment, the LCC28 came up to speed smoothly and the discharge pressure gauge pegged exactly at the planned 28 psi and stuck there without wavering. (It was the most perfect startup of all time! Surely something must require adjustment — no startup goes this well!) To add to the strangeness of the day, snow even started falling during the four hours of initial monitoring!

The amp draw, which was more than 55 for the competitor's pump, went down to 25 for the GIW pump using the same motor. The cement company is pleased with the savings of the installation, which includes this reduced energy consumption of 50 percent.

The success of this initial installation has led to the installation of eight more GIW pumps, which have systematically moved out all but three of the competitor's pumps at the cement plant. GIW now has units installed at the facility to carry out the following services:

1. Cement slurry transfer
2. Cement holding tank recirculation
3. Kiln feed pump

In addition, we're presently quoting a rod-mill-discharge system for the customer.

To learn more about how GIW products can reduce production expenses for your company, contact us at 1.888.TECHGIW (832-4449) or visit http://www.giwindustries.com.