Coal, O&M

Cooler cleaning method reduces time and expense

Issue 2 and Volume 100.

FIELD NOTES

Cooler cleaning method reduces time and expense

Cleaning and maintaining 30 heat exchanger coolers each year is no small task for Virginia Power`s Mt. Storm plant, which has 14 single-pass coolers, 12 double-pass lube oil coolers and four hydrogen coolers on the plant`s turbine and associated auxiliary equipment.

Previously, to keep the coolers in top condition, plant maintenance personnel would build scaffolding around each cooler, take off both cooler heads and manually rod and wash out debris. The process was slow and labor intensive, with an annual cost of $50,000 or more.

Virginia Power management began looking for a better way, researching alternative methods. A Slug Flush cleaning process from Hydro Chem Industrial Services was chosen. The cleaning process consists of dropping off only the outlet header on the bottom of the vertical single-pass coolers and installing a three-inch nominal pipe thread nipple on the inlet header after the cooler`s shutoff valve.

On the two-pass vertical coolers, HydroChem dropped off the inlet and outlet shutoff valves and installed three-inch nipples. The coolers were fed with 6- and 8-inch cooling water lines. The process required little or no scaffolding, increasing efficiency.

The Slug Flush method applies a frothed slug of water containing biodegradable degreasing and dispersant chemistry. Shots of the fluid dislodge sludge and debris from the cooler tubes. The frothed slugs of water are formed in a chamber and pushed through the heat exchanger with high velocity air bursts.

Cleaning the 30 coolers required only 36 hours, with a total cost of less than $250,000. The work was completed with the unit on line at reduced load while cleaning one exchanger at a time.

Measuring temperature and pressure drop showed heat exchange equipment performance to be equal to the results of the old mechanical method and visual inspection confirmed that the coolers` internal tubes were clean.

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Virginia Power`s Mt. Storm power plant