Earthwise Environmental, Bensenville, Ill., surveyed and inspected the process, finding that while the new equipment was top-notch, the equipment upgrade did not include proper commissioning and anticorrosion treatment of long sections of newly installed black iron piping.
Earthwise's engineering survey also found that the overall system contained numerous "dead legs" in piping runs as well as galvanic couples throughout the plant - factors contributing to bacteria buildup in the system. The water contained high iron and copper levels, and a low pH. In addition, Earthwise technicians discovered possible cross-connection and cross-contamination between the cooling tower and the chilled-water loop feeding water into the injection process.
To solve the multiple issues and reduce unnecessary production downtime, Earthwise confirmed the presence of sulfate-reducing bacteria (SRB) from the tower cross-connection and implemented on-line sterilization with a bio-dispersant and SRB biocide. A silica-polymer blend replaced existing nitrite treatment.
Once the system was sterilized, Earthwise developed a program to automate the feed of biocide/inhibitor and perform routine system-water biological testing.
The facility's review also resulted in equipment adjustments to improve overall efficiency and water quality. Dual filters were installed for the five molding machines to eliminate downtime during changes as well as labor costs. The existing 125-micron filtration system with a screen-type backwash filter was eliminated in favor of a 10-micron bag-type full-flow filter vessel. The series of galvanic couples were replaced with stainless steel manifolds, and a color-coded hose system was put in place to eliminate cross-contamination of the water tower and chilled-loop system.
The benefits of the changes were quickly felt. The injection molder realized the following improvements.
- Immediate
reduction in labor costs through the elimination of filter changes. Prior to
implementation of the Earthwise recommendations, facility employees spent an
average 20 minutes per filter change three times a week on five machines,
totaling six hours of labor weekly at a cost of $750 per hour. The filtration system
translated to more than $200,000 saved annually and a 60-day return on
investment, plus shorter production time.
- Changeover from galvanic
couples to stainless steel manifolds lowered the labor and capital costs
associated with corrosion and piping replacement.
- Long-term protection of
the chilled piping system eliminated the need for future replacement, a costly
capital expenditure.
- Reduced energy costs through increased heat transfer efficiencies due to elimination of the biofouling through the SRB biocide program.
