Finding hidden value at the bottom of a sediment tank

Crossposted from Clean Water Stories

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A big mechanical job at our West Point Treatment Plant replaced a special part of our sedimentation tanks. The sedimentation tanks are part of how we clean everyone’s sewer water.

What’s the real cost?

Have you ever been undecided when buying an appliance, trying to choose between a standard or select model? You probably wished you had some data to help you make an informed choice. Well, by studying costs and crunching the numbers, maintenance engineers at West Point determined that what looked like a higher priced option for certain replacement parts was actually the best value in the long run.

The cost of equipment isn’t just the cost of buying it. We work on being smart about how we take care of all our “stuff” and look at all of the costs, or “life-cycle” cost. We ask questions like:

  • What does it cost to buy it – or design and build it?
  • What does it cost to maintain / operate it – including labor and energy costs?
  • How long does it last?
  • What does it cost to recycle or dispose of it when we eventually replace it?

Investing in performance

When we clean wastewater, one of the steps is to let it flow slowly through sedimentation tanks, also called a settling tanks or clarifiers. It allows particles in the water to settle to the bottom as the water flows slowly through the tank.

At the bottom of the tanks, where all those particles are collecting, suction ducts sweep the floor, scooping up that settled sludge to move it to a different part of the plant for more treatment.

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Suction ducts sweep the floor of the tank, scooping up the particles that settle out of the sewer water (sludge) to move it to a different part of the plant for more treatment.

The now “old” suction ducts were a standard type back when they were installed. But their ‘plain steel’ was rusting and corroding – and the ducts were failing.

Our maintenance teams at West Point helped the ducts last longer by repeatedly applying galvanized and epoxy protective coatings over the years, but eventually they needed to be replaced.

Initially, it seemed that new stainless steel suction ducts might cost too much, but they’re highly resistant to corrosion, eliminating the need for overhauls and coatings every few years. Virtually rustproof, the amount of money we would save in lower maintenance offset the cost of the higher grade steel.

Cultivating mastery

Replacing heavy, crumbling, decades-old ducts requires technical expertise, and West Point maintenance crews were up to the task. Patrick Perrin, industrial maintenance mechanic, devised a method, with a few extra welds, that allowed a two person team to do the work of four. The work also provided valuable service time for industrial maintenance mechanic and project lead Mike Wallace to earn his Master Mechanic certification.

Working on our values

Replacing West Point clarifier suction ducts with cost efficient, stainless steel upgrades shows our employee’s commitment to finding innovative maintenance solutions and being responsible stewards of taxpayer dollars.

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Workers inspect the alignment of the new ducts.