Effective Cooling Tower Lay-up

By Ashish Gandhi
October 1999

The Author is is the Water Treatment and Mothballing Sales Manger at Cortec Corporation in St. Paul, MN. Mr. Gandhi (651-407-2770) is a chemical engineering graduate from University of Minnesota and a member of AIChE and NACE.

Introduction:

Every year, in Mid-West, it feels like fall and winter begins a week sooner than the previous year. For maintenance engineers, this first hint of fall signifies that the time to lay-up their cooling towers is fast approaching.

Most of the cooling towers in Mid-West are laid up dry. Towers are drained out to avoid water freezing in the system. Big and small water treatment companies usually treat cooling water, for a cooling tower, through out the year. When it comes to seasonal lay-up, most conventional methods fall far short of delivering the best combination of ease of use, economically, and environmentally sound program.

Problem:

Conventional seasonal lay-up programs often use an oil-based product that does not apply evenly; they can cause significant gunk balls in the equipment and these products poses a tough challenge of disposal. This practice is environmentally unsound. Another problem with using oil-based products is that they react with rubbers in the system and with roof tars. Oil-based products are a good source of nutrients for various kinds of bacteria, including anaerobic bacteria. This leads to promoting microbiological growth in the cooling tower system and hence bacterial corrosion.

The major shortcoming of conventional lay-up products is that they are strictly contact corrosion inhibitors (CCI). They can only protect the parts of the system that they contact. The overhead spaces, crevices and other such hard to reach spaces ends up being left unprotected. These parts of the system tend to corrode during the down time because they lack protection. Due to all of the above reasons it becomes important that a thorough cleaning of the system, using expensive chemicals, is done before commissioning the tower back for normal usage.

Solution:

There is a real need for a systematic and easy approach to lay-up cooling towers during down time. Cortec Corporation, (St Paul, MN) has devised an environmentally safe, inexpensive and easy way, which is far superior to conventional methods using oil-based products in cooling towers. These products will eliminate the use of hazardous chemicals for this process.

Cooling Tower Frogs & Cooling Loop Gator are two products that contain Cortecīs proprietary (Vapor Corrosion Inhibitor) VCI powders. Packaged in convenient water-soluble bags, they are perfect for seasonal or long-term lay-ups. VCI consist of blend of compounds that volatilize and create a VCI environment in the system. VCIs are adsorbed onto the metal surfaces forming a monomolecular layer. These protect both the anode and cathode sites of the metal surface. (See illustration)

Compared to conventional CCIs, Vapor Phase Corrosion Inhibitors protect not only in liquid phase (and hence as classic CCI) but also in vapor phase and at the interface of water and vapor, to protect surfaces in contact with air.

This unique approach enables VCIs to protect even small crevices from corrosion. Cortecīs VCIs are multi-metal formulation that protects various metals including galvanized steel.

Illustration

Method of application:

Dry Lay-up:

Flushing Lay-up:

Wet Lay-up:

Summary:

Cortecīs Cooling Tower Frog and Cooling Loop Gator provide:

There are many opportunities to improve cooling tower system efficiency through the use of chemical treatments. Protecting a cooling tower properly during a lay-up period is an important aspect of cooling tower operation. It can improve efficiency of the system during the operation and save the maintenance engineer lot of time and money if done right.

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Copyright © 1999, ECO Services International