Epoxy Repairs Corroded Pump
By Ian Goodland
Paper is a commodity that is often taken for granted. Most of us do not question its origin, nor do we concern ourselves with how it is produced. We simply write on it, fax it, mail it and maybe even shred it. Perhaps the only time we do not view...
By Ian Goodland
Paper is a commodity that is often taken for granted. Most of us do not question its origin, nor do we concern ourselves with how it is produced. We simply write on it, fax it, mail it and maybe even shred it. Perhaps the only time we do not view paper with a measure of indifference is when it appears as money. Yet even then, we do not value the actual paper, but rather what is printed upon it.
However, when you are in the business of manufacturing paper, you develop a certain appreciation for the pulp product. Prince George Pulp and Paper Ltd., a pulp and paper mill located in Prince George, B.C., understands this well. To Prince George Pulp, paper is a precious resource that is always in demand.
A subsidiary of Canadian-based Canfor Corporation, Prince George Pulp produces bleached, semi-bleached and unbleached kraft pulp, as well as bleached and unbleached kraft paper, for international distribution. The mill was built in 1965.
Prince George Pulp takes great pains to ensure that its manufacturing equipment operates at peak efficiency and is free from defects.
Consequently, when the primary Radiclone or “rad” pump developed holes in its steel casing, Prince George Pulp acted quickly. After all, this large centrifugal pump was essential to the manufacturing process, since it is used to pump pulp stock from a wirepit to the Radiclone cleaners.
According to Rick Nelson, maintenance planner for the machine room at Prince George Pulp, “During a routine plant shutdown, we discovered that hydrogen peroxide, an agent commonly used to bleach paper, corroded the pump and created gaping holes in the pump’s casing.”
“We tried patching the holes,” continued Nelson, “but soon discovered this was only a temporary solution. After four to six weeks, the peroxide would eat right through the patches. We decided that we had to either replace or restore the pump.”
Replacing the pump introduced a new set of problems. The damaged Radiclone pump was over 30 years old and would cost an exorbitant $180,000 to replace. Moreover, to replicate the design of this vintage pump, Prince George Pulp had to locate the original drawings in their corporate archives. All in all, installation would take as long as a year to complete.
“Obviously, we could not afford to wait a year for the new pump,” said Nelson. “In fact, each day that the problem went unresolved, we faced the possibility of a spontaneous plant shutdown.”
Prince George Pulp turned to a local industrial distributor, BC Bearing Engineers Ltd. of Burnaby, B.C., for help. After evaluating the severity of the pump’s corrosion, BC Bearing recommended an on-site evaluation by Devcon Corporation of Danvers, Mass. Devcon is a world leader in the manufacture of maintenance, repair and adhesive bonding technology.
To restore the pump, Devcon technicians implemented a timesaving, cost-effective repair process using the company’s Cleaner Blend 300, Brushable Ceramic, Ceramic Repair Putty and Wearguard Fine Load Epoxy.
First, the worn, damaged steel surface of the rad pump was grit-blasted, then cleaned with Cleaner Blend 300, a multi-purpose, non-trichlorethane degreaser used to clean heavy grease and oil deposits.
A primer coat was applied using Brushable Ceramic, high-precision repair epoxy that is corrosion, chemical and abrasion resistant. Formulated in two colours, red and blue, to ensure uniform coatings in multi-coat applications, Brushable Ceramic Red was used for the curing process.
After the larger holes were filled with Wearguard, the remaining cavities were filled with Ceramic Repair Putty. This alumina-filled epoxy compound is ideal for rebuilding and protecting processing equipment that has been exposed to corrosion, erosion, chemicals and acids.
To ensure that all cavities were filled, the Ceramic Repair Putty was applied to the entire casing.
“At this point the rad pump was nearly restored to pristine condition,” said Nelson, “and we could have resumed a normal manufacturing schedule. However, the Devcon technicians recommended one final, preventive repair application.” They applied a finish coat of Brushable Ceramic Blue. This provided a smooth, seamless protective barrier against future wear or chemical attack.
The blue colour is used to alert maintenance personnel. Any colour visible through the blue indicates that the topcoat is wearing off and the unit should be scheduled for repair.
“Our primary rad pump has been operating at peak efficiency since it was restored with Devcon’s repair solution,” said Nelson. “In fact, it’s been working so well that we will wait until our next major plant shutdown … to inspect the pump again.”
“Thanks to Devcon’s expertise, the primary rad pump has been reborn. Subsequently, we are considering Devcon products for other applications throughout our plant operations.”
Since the repair, the mill has continued to use the products for other repairs, and Devcon conducted several seminars on the process at the facility last year.
The repaired pump was eventually replaced (at a cost of $180,000) after a year in service, but it has been kept as a spare since it was showing no signs of wear.