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Extending System Service

Advanced corrosion of steel piping systems has become a serious and expensive problem to many facility managers and plant engineers.  At a growing number of commercial properties and process plants, high corrosion rates have forced the replacement of critical piping systems – some within as short a period of time as three or four years.  At others, it has created loss of service, equipment damage, excessive maintenance demands, high energy costs, major repairs, and overall unnecessary expense.

While lower quality pipe and restrictions on the use of specific corrosion inhibitors and biocides have clearly contributed to the problem, it remains a fact that many building properties and plant facilities regularly maintain open system corrosion levels in the 1 mil per year (MPY) and below range.  Excellent corrosion control and high operating efficiencies can, in fact, be achieved by carefully evaluating current operating conditions and implementing certain precautionary, and often necessary, changes.  Careful corrosion monitoring is critically important.

• Good Corrosion Control Possible

In order to prevent the damaging effects of uncontrolled corrosion, CorrView International strongly advises incorporating as many of the following general recommendations as feasible into any building operation and maintenance program.  While the benefits may not be immediately apparent, such steps will better ensure reliable and trouble free system operation over the long term.

• • • Evaluate the present status of the various piping systems using ultrasound to provide a baseline of corrosion activity.  Identify the existing corrosion rate, and past or present problems involving generalized corrosion, bacterial fouling, microbiologically induced corrosion (MIC), or pipe blockages, etc.
    • Develop a strict water treatment program which addresses the operating needs of the property.  Discuss specific concerns and solicit recommendations from your chemical water treatment contractor.  Avoid low bid situations as the sole criteria of selecting a water treatment contractor.  Maintain a detailed water treatment log book. Regularly review the results of the program with the water treatment contractor.
    • Establish a performance standard of corrosion loss tolerated for the water treatment contractor to meet.
    • Consider the services of an independent outside consultant or testing company to review all test results and evaluate the effectiveness of the chemical treatment program.
    • Fully automate all chemical feeds based upon cooling tower make-up water usage.  Automate biocide feed and blowdown.
    • Evaluate the layout of any open condenser water system for areas where sediment may accumulate to produce higher under deposit corrosion and focus any ultrasonic investigation in those areas.  Careful review of the piping system will help pinpoint common trouble areas to focus upon.
    • Mechanically clean all cooling tower basins twice per operating season, or more frequently if evidence of fouling or deposits exist.
    • Chemically clean and sterilize all open water systems twice per operating season.  Chemically clean and sterilize all closed systems every five years.
    • Install drip pan covers on the cooling tower in order to shield open water areas from direct sunlight, thereby reducing organic growth.
    • Substitute non-oxidizing biocides for oxidizing biocides such as chlorine and bromine.  Use oxidizing biocides for periodic sterilization only.
    • Eliminate any low flow areas within the piping system to prevent heavy particulates from depositing.  Horizontal piping, as well as the furthermost extremes of any circulating system, are particularly susceptible to the settling of deposits.  Other areas of concern are dead ends, by-pass lines, lead/lag equipment, future tie-in lines, free cooling heat exchangers, and abandoned piping, etc.
    • When possible, periodically run the circulating pumps at idle systems.  Higher corrosion rates are often identified in non-circulating systems.
    • Install side stream filtration to help control the buildup of particulates.  Both open and closed systems can greatly benefit from the volume of particulates removed by as little as 10% side stream filtration.  Full flow filtration is always preferred.
    • Install the take-off point to any filtration unit in a straight line to its flow, not perpendicular as predominantly exists.  Installing a tee in place of an elbow and reducing the straight through line to the filter while forcing the water to turn as normally will dramatically improve the filtration efficiency of any water filter.
    • Establish one or more centrally located spool pieces of 3 in. or greater diameter pipe which can be periodically removed for visual inspection.
    • Incorporate monthly biological plate count analysis into the regular chemical testing program.  Log and track the results.
    • Incorporate a supplemental chemical dispersing agent into the water treatment program for all systems.
    • Avoid draining down entire systems if possible during winter months.  Lay-up idle systems using a strong passivating agent or VIC inhibitor in order to prevent excess corrosion on unprotected metal surfaces.

• Fault Remains

In most ultrasonic investigations CorrView International has been involved, a major corrosion problem can be traced back to a failure to administer many of the above recommendations.  And the larger, more serious, and more expensive the corrosion problem – the more likely responsibility and blame is sought.

While in rare instances excellent corrosion control can be produced by purchasing a standard water treatment program and little else, such results are becoming far more rare due to the far greater negative influences against pipe which exist today.  Some of the best efforts toward producing an effective corrosion mitigation program have been met with failure due to special circumstances beyond an owner’s or operator’s control.

It is our strong opinion that added steps toward corrosion control are necessary today, rather than an option.  The benefits far outweigh the annual costs involved, and where the replacement of an entire piping system is the unfortunate end result, such preventative measures become invaluable in terms of money and careers saved.

© Copyright 2024 – William P. Duncan, CorrView International, LLC