QC Inspection

Uncured Coatings


One of the more interesting construction defects observed at a plant in Asia is a nearly universal application of coatings that did not cure.

As background, modern "paint" used in a power plant is a complex engineered product often applied in two or three layers. This is because each layer has a purpose. For example, inorganic zinc is often used as a primer, but not suitable as a top coat. Similarly, epoxy is used as a second coat, but not a top coat because it is poor at enduring UV unlike a urethane. 

Each of the layers must be properly mixed, and usually is catalyzed with a hardener. The proportion of hardener to base product is very important. Too little, the coating never cures and perpetually stays soft. It's a failed coating. Another important factor is to keep water (rain and condensation) from the coating components.  Water affects curing also.

At the plant in question, easily 70% of the coated plant (large coal plant) had coatings that were not cured.  To test this defect, ASTM has a MEK (Methyl Ethyl Ketone) wipe test which roughly involves a clean cloth, a little MEK, and... Read more

Contractor Savings

None.

Repair Costs

Collosal.  Left unrepaired...

Pillars of Salt & Sand (and Plastic)...


Piers are structural. This necessitates that they are installed correctly with every detail.

As with most construction defects, this is a simple problem of unskilled and unsupervised workers. The problem is compounded by a contractor culture that allows a QC program to run as a "paper" generating endeavor completely disassociated from the facts of field performance. In many cases, it's evident that there is no inspection. This is such a case...

Grout must be installed where to concrete conditions conform to the manufacturers recommendations to assure a strong bond between the materials (concrete and grout).  Typically, this involves a rough surface, clear of debris, and free of any existing concrete surface coating, and similar.

Well, in this case, it's hard to imagine how these piers ended up with plastic bags being embedded at the bonding joint, among other concerns.

One certainty, there was no engaged contractor QC or owner involvement.

Contractor Savings

Essentially none...

Repair Costs

In the future, the piers will need to be re-grouted as routine maintenance.  Unknown cost.

Settle for More!


In nearly every developing country location, plants evaluated by EPR have exhibited very poor performance of soil compaction, especially related to area paving.

At one facility, a more extensive review was conducted because significant settling was evident in dozens of areas. In the first photo, not only is the area paving soil consolidating, so is the soil below the pipe support foundation, which rendered the support ineffectual.  Some of the other pictures show images taken from a borescope beneath a slab where the soil had consolidated in the 12 months after the slab was poured. The findings included exposed rebar, construction debris, form work, voids, unconsolidated concrete, and improper slab thickness/finish. In all, technically nothing about the installation was acceptable.

In the last photo, a small crew can be observed preparing soil for finish grade.  It exhibits pretty well the nature of the problem.  Simply, the crew did not have the tools or knowledge to perform the work correctly. QC was also not likely to be involved to verify soil density.  However, it's a safe bet the QC... Read more

Contractor Savings

Minimal.

Repair Costs

Owner will live with poor conditions and possible operator injury.  Ongoing O&M cost.

Mechanical Damage


In many developing country locations, a recurring problem is the mechanical damage to otherwise properly applied coatings due to handling abuse.

For most plants, structural steel is shop (off site) fabricated, loaded on trucks or ships, and delivered to the construction site for erection.  This is an important process because it can become quite expensive and time consuming to field repair coatings.  This can be even more true in locations with high humidity because a proper repair must be effected within the coating manufacturers indicated limitations.  This is sometimes hard to achieve.

An owner should likewise be concerned because a repaired coating system is never as durable as the original coating.  The first photo shows a typical "handling" problem.  The subsequent photos show poor repairs and unrepaired damage.  Both are so common, it seems normal.

One plant in Asia had structural steel and piping that was so abused with mechaincal damage that the plant looked 15 years old even before COD.

Contractor Savings

Nothing.  It costs nothing to handle coated pipe/steel carefully.

Repair Costs

If all teh repairs were affected, it would have cost severeral tens of millions of $.

Inspection Futility


Often field quality suffers from a lack of oversight; quality control, supervision, or owner involvement.  Sometimes a contractor and owner set out to assure their interests are protected, but it fails anyway.

Using a large international source inspection firm tends to be where problems arise.  Those firms use local inspectors to keep costs down by limiting travel.  However, local inspectors are often the same people that visit particular shops and due to familiarity, a relationship develops which compromises the effectiveness of the shop inspection.  Instances exist in remote areas where inspectors are relatives of shop owners.  The main take-away, is that inspections by ineffective, conflicted, or technically limited personnel with no personal connection to your project is wrought with peril.

The opinion of the author is that if an inspection is worth performing by an owner, send your own people, or an inspector well known and hired directly.  It will be more cost than outsourcing with a large international inspection firm, but it will be worth it.

At one facility, the contractor... Read more

Contractor Savings

None.

Repair Costs

$150k +/- and wasted time.

Getting Touchy


Coatings are typically shop applied and touched up in the field.  On a large power station, there is considerable touch-up and it must be done correctly.

Briefly, as mentioned elsewhere in this Blog, coatings are not "paint", they are an engineered product that requires skilled personnel to apply properly.  In this case there are three coats in the system.  A zinc primer, epoxy mid-coat, followed by a urethane top coat.  Details... No coating will stick to steel substrate that is dirty, too smooth, or otherwise not prepared to the coating manufacturers requirements.  An epoxy mid-coat sticks well to a zinc primer, but does not stick to a urethane top coat.  If epoxy is left without a urethane top coat, it deteriorates from UV.  Urethane in most case needs to be applied over epoxy.

So, if a repair needs to be made, the existing paint needs to be taken off down to the primer, or mid-coat, depending on the damage.  However, epoxy (mid-coat) cannot be "slapped on" as to overlap onto existing urethane.  It will not stick.  Also, coatings cannot be applied over corrosion or dirt; seems obvious... Read more

Contractor Savings

No savings.

Repair Costs

Varies by plant, but to re-perform is significant.  If unrepaired, O&M is constantly painting, or lets plant rust.

Pinholes...


Engineered coating systems are complex, as mentioned in other postings.  When the manufacturer's recommendations are followed, these coatings are very good at preventing corrosion to the substrates.  However, if proper prep, mixing, contamination control, etc., is not followed there can be many different defects that render the coatings useless.

One such defect is known as "pinholes".  Often, or usually, this defect is not observable with the naked eye without magnification.  It's almost like worms ate holes down through the layers of coating.  Sometimes pinholes exist in a top coat, or maybe also the intermediate coating layer, but not penetrate the primer.  In other instances, the pinholes may extend all the way to the base metal.  If the coating is fairly new and pin point rusting is observed, chances are pretty good the pinhole goes to the base metal.

The remedy in such instances, is removal of the paint layer with the defect.  If the primer also exhibits the defect, all the coating material needs to be removed.  So, a "paint job" may look impeccable, but be a complete failure under... Read more

Contractor Savings

None.

Repair Costs

ROM - $25mm and a year of time by a well staffed painting contractor.