Quality Blog

Quality Blog Introduction

EPR’s project management, restructuring, and consulting experience is highly varied resulting in a unique industry perspective. Poorly managed construction may have many problems such as safety, schedule, escalated cost, etc... However, plant quality is the most significant determinant of the forward asset (plant) value.

This blog is not presented as deep technical reference but a discussion-level view.  It is assumed the more technical reader will understand the basis for these observations. However, our intention is to bring a real-world perspective of how construction quality impacts an owner, with enough technical content to provide context. If the reader wants to know more about a technical subject (i.e. PWHT of P91) please refer to the reference codes, standards, and specifications for your project (i.e. ASME).

All the problems identified in this Blog could have easily been avoided with skilled proactive oversight and usually minimal or no incremental cost.  If your project is near COD or early in construction and exhibiting some of these concerns or entering commissioning with a need to avoid enduring latent commissioning defects, EPR can help.

To discuss your project needs, please contact EPR...

Pipe Rack Bolting

The consequence of structural failure in a power plant is operationally serious and can be life threatening.
When structures are designed for bolted connections usually "high-strength" fasteners are indicated (ASTM A325/A490).  If these bolts are not installed properly, per the standard (AISC/RCSC, or other), the joint does not support the loads expected by the engineer.  So, when loose bolts are observed in completed facilities, it is alarming because it is an indicator the contractor's bolting program was flawed.  Properly installed bolts are verified to be pre-tensioned, which practically eliminates nuts backing off for any reason.

So what constitutes proper pre-tensioning?  The code guidelines are specific, however, in simple terms bolts must achieve a certain amount of stretch.  The complicating factor is that pre-tensioning varies depending on manufacturing lot, and environmental conditions like moisture because of variable thread friction.  This means that daily testing (for each lot) is required to determine a "torque value" for the assembly.  If this is not... Read more

Contractor Savings

Little or none.

Repair Costs

Contractor: RCSC arbitration is moderately expensive.  Owner: Risks structural failure and personnel injury.

Coatings Delamination

EPC Contract indicated “the project site is subjected to moist and heavily polluted salt laden air”…

While the contractor took precautions to properly specify the coating systems, the surface prep and coatings application was flawed anyway. Normally, an effective shop (or field) inspection program will catch the problem early and be resolved in favor an effective coating process. In this facility, there was extensive evidence that either no QC program existed, or the inspector(s) were compromised.

After 18 months in operation, the coatings appear 15 years old. To varying degrees, most of the structural steel coating systems in the subject plant are in a progressive state of failure with the substrates rapidly and increasingly unprotected. 

It was determined much of the steel coatings suffer from varying failure mechanisms.  However, this photo is an example of improper surface prep (NACE/SSPC) and inconsistent dry film thickness, often with a top-coat greatly exceeding manufacturers requirements.

Contractor Savings

Minimal to no cost savings. Some time may have been saved if rework in the shops had been required.

Repair Costs

Owner: Coating system will need an aggressive repair program as opposed to the anticipated touch-ups. Magnitude large but unknown.

General Welding

In a completed facility inspected by EPR, there was a noticeable level of unacceptable general welding.  As a frame of reference, this plant was purchased to be built by an experienced contractor to western standards (AWS) in a location where suitable labor was available.

During the initial stages of the review, it became clear that some workmanship lapses were so pervasive that a plant-wide cataloging of the defects was impractical.  Therefore, a detailed review was conducted on one power train to determine a representative condition of the whole plant related to general welding.  

171 welds on pipe supports, electrical cable tray/conduit supports, and gallery steel were evaluated per the visual acceptance criteria standards of AWS D1.1, Sections 5 and 6.  20 (twenty) were found to meet the most basic “stand-back” visual acceptance criteria of the AWS D1.1.  Effectively, at least 89% of the welds did not meet the AWS visual acceptance criteria, and many (most) failed with multiple defects.  Keep in mind this investigation did not get into real detail with the use of Cambridge or fillet... Read more

Contractor Savings

Clearly some money was saved, but it could not have been significant.

Repair Costs

Owner:  Could be as little as occasional maintenance labor for failed items, or significant when important failures occur costing operating hours/days.

HRSG Bolting

Large (HRSG) equipment erection is about attention to detail, but not overly complex. However, the structural and thermally cyclical nature of these units demands that proper methods and OEM instructions be observed.

In this case, a large new plant with 12 units was inspected one year after COD by EPR. There were so many deficiencies it is clear proper procedures were not followed. For high-strength bolting (ASTM A325/A490) proper pre-tension testing must occur, in addition to proper substrate alignment, thread engagement, and other details. The pertinent requirements, in addition to being code stipulated, were cascaded with clarity in the Contractor’s own specs and procedures, so they should have been followed and QC verified.

For both slip-critical and direct-tension applications bolting was observed to be missing, loose, installed in flame-cut holes, loose plies, and a variety of concerning problems. Over time, this condition will worsen and result in two safety concerns; falling fasteners, and unsafe structures.

Contractor Savings

Minimal.  It takes no more time to pretention bolting by the iron worker.  Further, QC checks should have been performed.

Repair Costs

Owner: Safety and outage concern. Repairs need to be affected.  EPCC: ~$25,000 per unit for equipment, new bolting, and man-lifts.

Not-So-Structural Grating

After noticing an unusual number of severe workmanship issues with grating penetrations, a study was conducted on one portion of a recently visited facility (one power block).

In the subject area, 231 penetrations through grating or deck plate did not conform to the requirements of contractor’s own Structural Erection Procedure, which states that all cuts of 3 grating bearing-bars shall be banded, and further, that field-cut openings shall clear insulation by 1”.  The contractor’s own structural drawings also indicate a requirement/detail showing the penetrations of grating and checker plate reinforced with toe plate and banding.

Of the 231 inspections, 39 were missing banding, 174 had no toe plate, 10 did not meet the required insulation clearance, and 8 open holes were left in the grating.  In total, roughly 100% of the penetrations were out of compliance with normal practice and the contractor’s criteria indicated above.

More concerning, is that the workmanship is so poor in some instances that almost none of the bearing-bars remain intact leaving the structural integrity of the... Read more

Contractor Savings

Labor/Supervision savings and probably some material.

Repair Costs

Contractor:  Some material expense and labor.  Scaffold in some locations perhaps.  Owner: Risks injuring O&M personnel or worse.

Steam Vents at Platform

EPR observed that steam safety valves had lifted at some period in the past during a load transient. The energy from an un-silenced steam release at 1,000F is violent and typically includes a powerful supersonic noise wave. Debris remains impaled on nearby structural steel and equipment from the force of the previous steam discharge.

A serious safety concern is that a personnel access platform is above and adjacent to the five (5) vent stacks. If any personnel would have been located on the platform during a release, they would have no doubt been seriously injured and burned. The owner's operators are exposed to a serious risk until this condition is resolved.

This safety problem persists because of a failure of engineering, piping construction, and the contractors commissioning team to resolve the issue prior to COD.

This is a very dangerous design and all 5 relief valve vents need to be extended above the structure or vented away from the access area.

Contractor Savings

Minimal cost to extend the vent stacks to a safe elevation.

Repair Costs

Owner: Potential O&M personnel injury or fatality with associated costs. Contractor: Minimal cost to extend the vent stacks to a safe elevation.

HRSG Stack Welding

HRSG Stacks are subjected to accelerated corrosion where sulfur is present in the fuel (gas/oil). An engineered solution is to protect stack internals with a coating which contains glass flake. For the coating to adhere it must be applied on a properly prepared substrate (NACE/SSPC/Manufacturer’s Recommendations). Glass flake coatings cannot be effectively patched.  

In this case, the stack field welds were not compliant with AWS D1.1, 5.24.4 (visual examination criteria), the construction contract criteria. This poor workmanship necessitated rework of the welds and stack coatings. Concerns include welder qualification, lack of weld inspection, lack of coatings prep inspection, and pervasiveness of defect (full length, all stacks). Additionally, the stack alignment lugs were not ground smooth in preparation for the coatings.

Another concern with unacceptable weld profiles in the stack is weld failure due to expansion and contraction of the stack during outage cycles and wind loads, especially in the presence of sulfur.

Blasting, weld repair, and recoating of one stack... Read more

Contractor Savings

Minimal. It takes no more time to weld properly, but perhaps some minor labor savings was gained with an unqualified welder

Repair Costs

Owner: 2 month outage, revenue loss at $35,000/day =~$2,000,000. EPCC: ~$400,000 to repair welds and recoat.

Weld Slugs

Proper power plant construction is typically based on layers of processes and checks.  Often observed quality problems are concerning due to their possible systematic nature and origin as a supervision problem.

In the realm of field welding, few defects speak as clearly about poor contractor quality and a loss of accountability than a slugged weld.  The attached photo reveals that a piece of “all-thread” rod was used to fill several weld passes.  Even worse, the welder didn’t even feel compelled to bury the slug under the cap and so it remained exposed.  This indicates a site ethic existed, where the welder felt there was no consequence to being caught, or perhaps the welder was confident that no one would verify his work.

There may be several codes or standards that cover this type of activity, but it violates the general welding standards of AWS.  The practical reason “slugs” are not acceptable is due to the uncontrolled and usually low-grade nature of the material used as “slugs”.  This implies a possible structural deficiency, which is of course not acceptable.

In this facility,... Read more

Contractor Savings

The joints need welding, to do it wrong saves no time.  Unqualified labor may be marginally cheaper, but not if the work is rejected!

Repair Costs

Contractor: Cost of repair is small; but brand damage is meaningful.  Owner:  Structural failure risk increases, but small. Concerning indicator of plant quality!

Galvanized Hardware (Or Not)

When a plant is built in a moist, heavily polluted, and/or salt laden environment, corrosion protection is a serious consideration.  At a minimum, hot dipped galvanized hardware (nuts, bolts, washers, clips, etc.) is usually specified for outdoor service.

In a recently visited new facility, aggressive corrosion was exhibited almost universally on the hardware.  What was discovered is that wherever galvanized was specified, electro-galvanized, electroplated zinc, or zinc plated, (different terms, same thing) was substituted by the contractor.  This results in a 3 to 12 micron coating that gives it a much lower degree of corrosion protection than hot dipped galvanized with an 85 to 90 micron layer of zinc. IEC indicates these coatings degrade (in this environment) at 4-8 microns/year.  It's then easy to see why there is so much aggressive corrosion and advancing stages of metal loss after only a couple years.

In the rare cases where hot dipped galvanized was provided, it seemed to perform well.

Contractor Savings

Marginal material cost savings; No labor savings.

Repair Costs

Contractor: Substantial cost (Labor/Material) to replace fasteners in bulk.  Owner: Fasteners failing is significant.  Electrical system risks increase over time. 

Dirt... and Fuel Gas

As background, one critical system in a power plant is fuel gas.  Typically, every system is cleaned to a condition that is nearly spotless.  This is especially true of fuel gas because it feeds the turbines and duct burners.  EPR evaluated a plant that was physically very large.  The fuel gas header was 1.5+ miles long, inside the plant downstream of the supplier custody-filters.  The system changed elevations, had countless fittings, and pipe size changes.  Clearly, this is a difficult system configuration to clean well for an inexperienced crew.

Prior to EPR being involved, roughly 50 warranty claims were raised against the EPC contractor that enumerated roughly 300+ failures of valves, flame scanners, regulators, and really anything in the system with a seat or rubber O-ring.  The EPC contractor refused to address the issue on-the-whole with a proper RCA (root-cause analysis), instead dealing with each item as if unrelated.

The attached photographs tell the story.  This system is so full of dirt and contamination that it's not defensible to indicate proper, or perhaps any, commissioning... Read more

Contractor Savings

No Savings.  Contractor went through "motions" of cleaning system, just didn't!

Repair Costs

Just in terms of Owner down-time for needless repairs this is millions of $'s.  Parts, labor, etc...