The facility was facing a number of issues, including: excessive equipment corrosion by contact cooling water (CCW), excessive leakage from hydraulic system into CCW, excessive makeup water use, excessive energy use to pump groundwater for makeup water, excessive costs incurred from hydraulic fluid replacement, equipment repair and replacement, water chemicals, energy and downtime.
Problems were first realized in mid 2007 when corrosion rate began to compromise the structural steel in our caster spray chamber and other locations. Corrosion coupons confirmed this with readings of 7.7 mils/yr. Root cause analysis showed:
1. Hydraulic fluid system leakage enters contact cooling water (CCW) via indoor CCW water flumes.
2. Hydraulic fluid acts as food source for microorganisms that quickly multiply as food source increases.
3. Large bleach (12% sodium hypochlorite) additions required to control microorganism growth.
4. Increased salt concentration increases CCW corrosivity.
5. Hydraulic fluids and salt cause increased CCQW turbidity and conductivity requiring increased CCW blow down requiring increased groundwater use for makeup.
A pollution prevention team was formed.
A daily report card was developed to illustrate hydraulic fluids loss rates from the Melt Shop, TX I and TX Roll Mills.This information was communicated to the entire team daily. An aggressive training program was given to all team members encouraging leak identification and repair. The training stressed that one gallon of hydraulic fluid leaked into the CCW generates a cost of $7 ($5 to replace and $2 to treat). In 2007, 72,000 gallons of hydraulic fluid leaked into the CCW system. This was a direct loss of $504,000 for that year.
Details of Reductions
Additional Information :
Nucor Steel Texas manufactures 1 million tons per year of rebar, angle, flat, round and square bar products from scrap steel using electric arc furnace, continuous casting and rolling technologies.